ORCID Profile
0000-0002-7625-562X
Current Organisation
University of Western Australia
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Astronomical and Space Sciences | Cosmology and Extragalactic Astronomy | Photonics, Optoelectronics and Optical Communications | Galactic Astronomy | Astronomical and Space Instrumentation
Expanding Knowledge in the Physical Sciences | Scientific Instruments | Expanding Knowledge in Technology | Electronic Information Storage and Retrieval Services |
Publisher: Oxford University Press (OUP)
Date: 19-02-2020
Abstract: We use the extended GALEX Arecibo SDSS Survey (xGASS) to quantify the relationship between atomic hydrogen (H i) reservoir and current star formation rate (SFR) for central disc galaxies. This is primarily motivated by recent claims for the existence, in this s le, of a large population of passive discs harbouring H i reservoirs as large as those observed in main-sequence galaxies. Across the stellar mass range 109 & M*/M⊙ & 1011, we practically find no passive (≳2σ below the star forming main sequence) disc galaxies with H i reservoirs comparable to those typical of star-forming systems. Even including H i non-detections at their upper limits, passive discs typically have ≥0.5 dex less H i than their active counterparts. We show that previous claims are due to the use of aperture-corrected SFR estimates from the MPA/JHU SDSS DR7 catalogue, which do not provide a fair representation of the global SFR of H i-rich galaxies with extended star-forming discs. Our findings confirm that the bulk of the passive disc population in the local Universe is H i-poor. These also imply that the reduction of star formation, even in central disc galaxies, has to be accompanied by a reduction in their H i reservoir.
Publisher: Oxford University Press (OUP)
Date: 13-01-2017
DOI: 10.1093/MNRAS/STX046
Publisher: Oxford University Press (OUP)
Date: 13-06-2012
Publisher: Oxford University Press (OUP)
Date: 22-09-2018
Publisher: Oxford University Press (OUP)
Date: 25-11-2020
Abstract: We perform a joint analysis of high spatial resolution molecular gas and star-formation rate (SFR) maps in main-sequence star-forming galaxies experiencing galactic-scale outflows of ionized gas. Our aim is to understand the mechanism that determines which galaxies are able to launch these intense winds. We observed CO(1→0) at 1-arcsec resolution with ALMA in 16 edge-on galaxies, which also have 2-arcsec spatial-resolution optical integral field observations from the SAMI Galaxy Survey. Half the galaxies in the s le were previously identified as harbouring intense and large-scale outflows of ionized gas (‘outflow types’) and the rest serve as control galaxies. The data set is complemented by integrated CO(1→0) observations from the IRAM 30-m telescope to probe the total molecular gas reservoirs. We find that the galaxies powering outflows do not possess significantly different global gas fractions or star-formation efficiencies when compared with a control s le. However, the ALMA maps reveal that the molecular gas in the outflow-type galaxies is distributed more centrally than in the control galaxies. For our outflow-type objects, molecular gas and star-formation are largely confined within their inner effective radius (reff), whereas in the control s le, the distribution is more diffuse, extending far beyond reff. We infer that outflows in normal star-forming galaxies may be caused by dynamical mechanisms that drive molecular gas into their central regions, which can result in locally enhanced gas surface density and star-formation.
Publisher: Oxford University Press (OUP)
Date: 16-12-2022
Abstract: Observations of the neutral atomic hydrogen (${\\rm H\\, {\\small I}}$) gas in galaxies are predominantly spatially unresolved, in the form of a global ${\\rm H\\, {\\small I}}$ spectral line. There has been substantial work on quantifying asymmetry in global ${\\rm H\\, {\\small I}}$ spectra (‘global ${\\rm H\\, {\\small I}}$ asymmetry’), but due to being spatially unresolved, it remains unknown what physical regions of galaxies the asymmetry traces, and whether the other gas phases are affected. Using optical integral field spectrograph (IFS) observations from the Sydney AAO Multi-object IFS (SAMI) survey for which global ${\\rm H\\, {\\small I}}$ spectra are also available (SAMI-${\\rm H\\, {\\small I}}$), we study the connection between asymmetry in galaxies’ ionized and neutral gas reservoirs to test if and how they can help us better understand the origin of global ${\\rm H\\, {\\small I}}$ asymmetry. We reconstruct the global Hα spectral line from the IFS observations and find that while some global Hα asymmetries can arise from disturbed ionized gas kinematics, the majority of asymmetric cases are driven by the distribution of Hα-emitting gas. When compared to the ${\\rm H\\, {\\small I}}$, we find no evidence for a relationship between the global Hα and ${\\rm H\\, {\\small I}}$ asymmetry. Further, a visual inspection reveals that cases where galaxies have qualitatively similar Hα and ${\\rm H\\, {\\small I}}$ spectral profiles can be spurious, with the similarity originating from an irregular 2D Hα flux distribution. Our results highlight that comparisons between global Hα and ${\\rm H\\, {\\small I}}$ asymmetry are not straightforward, and that many global ${\\rm H\\, {\\small I}}$ asymmetries trace disturbances that do not significantly impact the central regions of galaxies.
Publisher: American Astronomical Society
Date: 2023
Publisher: Oxford University Press (OUP)
Date: 15-04-2021
Abstract: Observations have revealed that disturbances in the cold neutral atomic hydrogen (H i) in galaxies are ubiquitous, but the reasons for these disturbances remain unclear. While some studies suggest that asymmetries in integrated H i spectra (global H i asymmetry) are higher in H i-rich systems, others claim that they are preferentially found in H i-poor galaxies. In this work, we utilize the Arecibo Legacy Fast ALFA (ALFALFA) and extended GALEX Arecibo SDSS Survey (xGASS) surveys, plus a s le of post-merger galaxies, to clarify the link between global H i asymmetry and the gas properties of galaxies. Focusing on star-forming galaxies in ALFALFA, we find that elevated global H i asymmetry is not associated with a change in the H i content of a galaxy, and that only the galaxies with the highest global H i asymmetry show a small increase in specific star formation rate (sSFR). However, we show that the lack of a trend with H i content is because ALFALFA misses the ‘gas-poor’ tail of the star-forming main-sequence. Using xGASS to obtain a s le of star-forming galaxies that is representative in both sSFR and H i content, we find that global H i asymmetric galaxies are typically more gas-poor than symmetric ones at fixed stellar mass, with no change in sSFR. Our results highlight the complexity of the connection between galaxy properties and global H i asymmetry. This is further confirmed by the fact that even post-merger galaxies show both symmetric and asymmetric H i spectra, demonstrating that merger activity does not always lead to an asymmetric global H i spectrum.
Publisher: Cambridge University Press (CUP)
Date: 06-2007
DOI: 10.1017/S174392130701438X
Abstract: The Arecibo L-band Feed Array Zone of Avoidance Survey (ALFA ZOA) will map 1350-1800 deg 2 at low Galactic latitude, providing HI spectra for galaxies in regions of the sky where our knowledge of local large scale structure remains incomplete, owing to obscuration from dust and high stellar confusion near the Galactic plane. Because of these effects, a substantial fraction of the galaxies detected in the survey will have no optical or infrared counterparts. However, near infrared follow up observations of ALFA ZOA sources found in regions of lowest obscuration could reveal whether some of these sources could be objects in which little or no star formation has taken place (“dark galaxies”). We present here the results of ALFA ZOA precursor observations on two patches of sky totaling 140 deg 2 (near l = 40°, and l = 192°). We have measured HI parameters for detections from these observations, and cross-correlated with the NASA/IPAC Extragalactic Database (NED). A significant fraction of the objects have never been detected at any wavelength. For those galaxies that have been previously detected, a significant fraction have no previously known redshift, and no previous HI detection.
Publisher: Elsevier BV
Date: 11-2011
DOI: 10.1016/J.IJNURSTU.2011.05.011
Abstract: The interests of users should lead service developments. However, it has been claimed that forensic mental health services have largely ignored examining users' views on the nature and quality of the service offered to them. Perceived social climate and perceived therapeutic relationship are viewed as important indicators of treatment outcome however previous findings about how these variables may be associated with satisfaction with forensic services are equivocal. This study aims to assess the levels of service user satisfaction in forensic in-patient settings in one mental health trust and explore how the perceived therapeutic relationship of the service users with their key-workers and the perceived social climate of the wards are associated with service user satisfaction. A cross-sectional survey design was chosen and an independent researcher facilitated the completion of three standardised assessments measuring service user satisfaction, therapeutic relationships and the social climate of the ward. Forty-four service users detained in secure settings completed the standardised assessments. The study was conducted in four medium secure and three low secure units in one NHS mental health trust. The data was analysed to examine the level of satisfaction with services and how both the therapeutic relationship and the ward environment were related to levels of satisfaction. The majority of service users who responded were generally satisfied with services "rehabilitation" and "perceived safety" were viewed most positively. Service users' perceptions about the social climate of the ward were found to have a significant relationship with service users' satisfaction with forensic services. However, the variables with the strongest association with satisfaction with forensic services are service users' perceptions about the nature of therapeutic relations with staff. This study indicates that service users' satisfaction with forensic services is strongly associated with their experiences of the therapeutic relationship with their key-workers and the social climate of the ward. The findings emphasize the importance of forming and maintaining effective therapeutic relations and reinforce the need to maintain a therapeutic environment free of aggressive tension and threats of violence. The results also highlight the potential for service users to be dissatisfied with their financial situation following admission.
Publisher: American Astronomical Society
Date: 20-04-2007
DOI: 10.1086/516635
Publisher: Oxford University Press (OUP)
Date: 28-06-2018
Publisher: American Astronomical Society
Date: 09-2022
Abstract: We present new results of a 12 CO( J = 1–0) imaging survey using the Atacama Compact Array (ACA) for 31 H i detected galaxies in the IC 1459 and NGC 4636 groups. This is the first CO imaging survey for loose galaxy groups. We obtained well-resolved CO data (∼0.7–1.5 kpc) for a total of 16 galaxies in two environments. By comparing our ACA CO data with the H i and UV data, we probe the impacts of the group environment on the cold gas components (CO and H i gas) and star formation activity. We find that CO and/or H i morphologies are disturbed in our group members, some of which show highly asymmetric CO distributions (e.g., IC 5264, NGC 7421, and NGC 7418). In comparison with isolated galaxies in the xCOLD GASS s le, our group galaxies tend to have low star formation rates and low H 2 gas fractions. Our findings suggest that the group environment can change the distribution of cold gas components, including the molecular gas and star formation properties of galaxies. This is supporting evidence that preprocessing in the group-like environment can play an important role in galaxy evolution.
Publisher: Cambridge University Press (CUP)
Date: 2023
DOI: 10.1017/PASA.2023.14
Abstract: The quenching of cluster satellite galaxies is inextricably linked to the suppression of their cold interstellar medium (ISM) by environmental mechanisms. While the removal of neutral atomic hydrogen (H i ) at large radii is well studied, how the environment impacts the remaining gas in the centres of galaxies, which are dominated by molecular gas, is less clear. Using new observations from the Virgo Environment traced in CO survey (VERTICO) and archival H i data, we study the H i and molecular gas within the optical discs of Virgo cluster galaxies on 1.2-kpc scales with spatially resolved scaling relations between stellar ( $\\Sigma_{\\star}$ ), H i ( $\\Sigma_{\\text{H}\\,{\\small\\text{I}}}$ ), and molecular gas ( $\\Sigma_{\\text{mol}}$ ) surface densities. Adopting H i deficiency as a measure of environmental impact, we find evidence that, in addition to removing the H i at large radii, the cluster processes also lower the average $\\Sigma_{\\text{H}\\,{\\small\\text{I}}}$ of the remaining gas even in the central $1.2\\,$ kpc. The impact on molecular gas is comparatively weaker than on the H i , and we show that the lower $\\Sigma_{\\text{mol}}$ gas is removed first. In the most H i -deficient galaxies, however, we find evidence that environmental processes reduce the typical $\\Sigma_{\\text{mol}}$ of the remaining gas by nearly a factor of 3. We find no evidence for environment-driven elevation of $\\Sigma_{\\text{H}\\,{\\small\\text{I}}}$ or $\\Sigma_{\\text{mol}}$ in H i -deficient galaxies. Using the ratio of $\\Sigma_{\\text{mol}}$ -to- $\\Sigma_{\\text{H}\\,{\\small\\text{I}}}$ in in idual regions, we show that changes in the ISM physical conditions, estimated using the total gas surface density and midplane hydrostatic pressure, cannot explain the observed reduction in molecular gas content. Instead, we suggest that direct stripping of the molecular gas is required to explain our results.
Publisher: Oxford University Press (OUP)
Date: 27-09-2023
Publisher: Oxford University Press (OUP)
Date: 28-11-2023
Abstract: We examine the H i gas kinematics of galaxy pairs in two clusters and a group using Australian Square Kilometre Array Pathfinder (ASKAP) WALLABY pilot survey observations. We compare the H i properties of galaxy pair candidates in the Hydra I and Norma clusters, and the NGC 4636 group, with those of non-paired control galaxies selected in the same fields. We perform H i profile decomposition of the s le galaxies using a tool, baygaud, which allows us to deblend a line-of-sight velocity profile with an optimal number of Gaussian components. We construct H i superprofiles of the s le galaxies via stacking of their line profiles after aligning the central velocities. We fit a double Gaussian model to the superprofiles and classify them as kinematically narrow and broad components with respect to their velocity dispersions. Additionally, we investigate the gravitational instability of H i gas discs of the s le galaxies using Toomre Q parameters and H i morphological disturbances. We investigate the effect of the cluster environment on the H i properties of galaxy pairs by iding the cluster environment into three subcluster regions (i.e. outskirts, infalling, and central regions). We find that the denser cluster environment (i.e. infalling and central regions) is likely to impact the H i gas properties of galaxies in a way of decreasing the litude of the kinematically narrow H i gas ($M_{\\rm {narrow}}^{\\rm {H\\, \\small {\\rm I}}}$/$M_{\\rm {total}}^{\\rm {H\\, \\small {\\rm I}}}$), and increasing the Toomre Q values of the infalling and central galaxies. This tendency is likely to be more enhanced for galaxy pairs in the cluster environment.
Publisher: Oxford University Press (OUP)
Date: 30-06-2011
Publisher: American Astronomical Society
Date: 05-1998
DOI: 10.1086/300314
Publisher: Cambridge University Press (CUP)
Date: 2022
DOI: 10.1017/PASA.2022.43
Abstract: We present the Widefield ASKAP L-band Legacy All-sky Blind surveY (WALLABY) Pilot Phase I H i kinematic models. This first data release consists of H i observations of three fields in the direction of the Hydra and Norma clusters, and the NGC 4636 galaxy group. In this paper, we describe how we generate and publicly release flat-disk tilted-ring kinematic models for 109/592 unique H i detections in these fields. The modelling method adopted here—which we call the WALLABY Kinematic Analysis Proto-Pipeline (WKAPP) and for which the corresponding scripts are also publicly available—consists of combining results from the homogeneous application of the FAT and 3DBarolo algorithms to the subset of 209 detections with sufficient resolution and $S/N$ in order to generate optimised model parameters and uncertainties. The 109 models presented here tend to be gas rich detections resolved by at least 3–4 synthesised beams across their major axes, but there is no obvious environmental bias in the modelling. The data release described here is the first step towards the derivation of similar products for thousands of spatially resolved WALLABY detections via a dedicated kinematic pipeline. Such a large publicly available and homogeneously analysed dataset will be a powerful legacy product that that will enable a wide range of scientific studies.
Publisher: American Astronomical Society
Date: 14-02-2020
Publisher: Oxford University Press (OUP)
Date: 16-02-2018
DOI: 10.1093/MNRAS/STY387
Publisher: American Astronomical Society
Date: 20-12-2016
Publisher: Annual Reviews
Date: 18-08-2022
DOI: 10.1146/ANNUREV-ASTRO-021022-043545
Abstract: The cold interstellar medium (ISM) plays a central role in the galaxy evolution process. It is the reservoir that fuels galaxy growth via star formation, the repository of material formed by these stars, and a sensitive tracer of internal and external processes that affect entire galaxies. Consequently, significant efforts have gone into systematic surveys of the cold ISM of the galaxies in the local Universe. This review discusses the resulting network of scaling relations connecting the atomic and molecular gas masses of galaxies with their other global properties (stellar masses, morphologies, metallicities, star-formation activity…) and their implications for our understanding of galaxy evolution. Key take-home messages are as follows: ▪ From a gas perspective, there are three main factors that determine the star-formation rate of a galaxy: the total mass of its cold ISM, how much of that gas is molecular, and the rate at which any molecular gas is converted into stars. All three of these factors vary systematically across the local galaxy population. ▪ The shape and scatter of both the star-formation main sequence and the mass–metallicity relation are deeply linked to the availability of atomic and molecular gas. ▪ Future progress will come from expanding our exploration of scaling relations into new parameter space (in particular, the regime of dwarf galaxies), better connecting the cold ISM of large s les of galaxies with the environment that feeds them (the circumgalactic medium, in particular), and understanding the impact of these large scales on the efficiency of the star-formation process on molecular cloud scales.
Publisher: Oxford University Press (OUP)
Date: 14-09-2023
Publisher: Oxford University Press (OUP)
Date: 12-01-2017
DOI: 10.1093/MNRAS/STX053
Publisher: American Astronomical Society
Date: 09-10-2017
Publisher: Cambridge University Press (CUP)
Date: 08-2006
DOI: 10.1017/S1743921306006028
Abstract: The Arecibo Galaxy Environment Survey (AGES, Auld et al . 2006) will map ~200 square degrees over the next years using the ALFA feed array at the 305-m Arecibo Telescope. AGES is specifically designed to investigate various galactic environments from local voids to interacting groups and cluster of galaxies. AGES will map 20 square degrees in the Coma-Abell1367 supercluster including the Abell cluster 1367 and its outskirts (up to ~2 virial radii). In Spring 2006 we nearly completed the observations of 5 square degrees in the range 11:34 RA 11:54, 19:20 Dec :20 covering all the cluster core and part of its infalling region reaching a 5 sigma detection limit of M(HI)~4×10 8 M ⊙ (assuming a velocity width ~200 km~s −1 ) at the distance of Abell1367 (~92 Mpc). An HI selected s le has been extracted from the datacube obtaining a catalogue of fluxes, recessional velocities, positions and velocity widths. We present a preliminary analysis of the properties of the HI sources and report the discovery of HI diffuse features within interacting groups at the periphery of Abell1367.
Publisher: Oxford University Press (OUP)
Date: 29-01-2020
Abstract: We use H i and H2 global gas measurements of galaxies from xGASS and xCOLD GASS to investigate quenching paths of galaxies below the Star forming main sequence (SFMS). We show that the population of galaxies below the SFMS is not a 1:1 match with the population of galaxies below the H i and H2 gas fraction scaling relations. Some galaxies in the transition zone (TZ) 1σ below the SFMS can be as H i-rich as those in the SFMS, and have on average longer gas depletion time-scales. We find evidence for environmental quenching of satellites, but central galaxies in the TZ defy simple quenching pathways. Some of these so-called ‘quenched’ galaxies may still have significant gas reservoirs and be unlikely to deplete them any time soon. As such, a correct model of galaxy quenching cannot be inferred with star formation rate (or other optical observables) alone, but must include observations of the cold gas. We also find that internal structure (particularly, the spatial distribution of old and young stellar populations) plays a significant role in regulating the star formation of gas-rich isolated TZ galaxies, suggesting the importance of bulges in their evolution.
Publisher: Oxford University Press (OUP)
Date: 14-05-2021
Abstract: We present results from neutral atomic hydrogen (H i) observations of Hydra I, the first cluster observed by the Widefield ASKAP L-band Legacy All-sky Blind Survey (WALLABY) on the Australian Square Kilometre Array Pathfinder. For the first time, we show that WALLABY can reach its final survey sensitivity. Leveraging the sensitivity, spatial resolution, and wide field of view of WALLABY, we identify a galaxy, ESO 501−G075, that lies near the virial radius of Hydra I and displays an H i tail. ESO 501−G075 shows a similar level of morphological asymmetry as another cluster member, which lies near the cluster centre and shows signs of experiencing ram pressure. We investigate possible environmental processes that could be responsible for producing the observed disturbance in the H i morphology of ESO 501−G075. We rule out tidal interactions, as ESO 501−G075 has no nearby neighbours within ∼0.34 Mpc. We use a simple model to determine that ram pressure can remove gas from the disc at radii r ≳ 25 kpc. We conclude that, as ESO 501−G075 has a typical H i mass compared to similar galaxies in the field and its morphology is compatible with a ram pressure scenario, ESO 501−G075 is likely recently infalling into the cluster and in the early stages of experiencing ram pressure.
Publisher: Oxford University Press (OUP)
Date: 05-12-2015
Publisher: Oxford University Press (OUP)
Date: 26-04-2016
DOI: 10.1093/MNRAS/STW801
Publisher: American Astronomical Society
Date: 02-2006
DOI: 10.1086/498713
Publisher: Oxford University Press (OUP)
Date: 29-11-2021
Abstract: The combination of gas-phase oxygen abundances and stellar metallicities can provide us with unique insights into the metal enrichment histories of galaxies. In this work, we compare the stellar and gas-phase metallicities measured within a 1Re aperture for a representative s le of 472 star-forming galaxies extracted from the SAMI Galaxy Survey. We confirm that the stellar and interstellar medium (ISM) metallicities are strongly correlated, with scatter ∼3 times smaller than that found in previous works, and that integrated stellar populations are generally more metal-poor than the ISM, especially in low-mass galaxies. The ratio between the two metallicities strongly correlates with several integrated galaxy properties including stellar mass, specific star formation rate, and a gravitational potential proxy. However, we show that these trends are primarily a consequence of: (a) the different star formation and metal enrichment histories of the galaxies, and (b) the fact that while stellar metallicities trace primarily iron enrichment, gas-phase metallicity indicators are calibrated to the enrichment of oxygen in the ISM. Indeed, once both metallicities are converted to the same ‘element base’ all of our trends become significantly weaker. Interestingly, the ratio of gas to stellar metallicity is always below the value expected for a simple closed-box model, which requires that outflows and inflows play an important role in the enrichment history across our entire stellar mass range. This work highlights the complex interplay between stellar and gas-phase metallicities and shows how care must be taken in comparing them to constrain models of galaxy formation and evolution.
Publisher: American Astronomical Society
Date: 04-2006
DOI: 10.1086/500171
Publisher: IOP Publishing
Date: 30-08-2022
Abstract: This paper presents data from a 21 cm H i emission drift scan observation of a field partially covering the NGC 4636 galaxy group with the Five-hundred meter Aperture Radio Telescope (FAST). We construct a pipeline to reduce the data, and use SoFiA for source finding. When not contaminated by Radio Frequency Interference (RFI), the FAST observations are capable of detecting all of the galaxies previously detected by the Arecibo Legacy Fast ALFA (ALFALFA) survey in the same region. Comparing to ALFALFA for the detections in common, the FAST data show consistent integrated spectra when the H i disks are spatially unresolved, and capture more flux when the H i disks are resolved. The FAST data further reveal 10 new detections in the region mutually covered with ALFALFA, and 18 new detections beyond the footprint of ALFALFA. All of the new detections have the matching optical counterparts. For the member galaxies of the NGC 4636 group, the detection limit of FAST is deeper by 0.4 dex in H i mass than that of the ALFALFA data. After correcting for the incompleteness caused by RFI contamination, we show that the H i detection rate of galaxies rises steeply with radius out to the virial radius of the group, and flattens beyond that. We also examine four spatially resolved galaxy systems with potential tidal interaction features in detail. Considering that the data have been taken during the “shared-risk” period before a major source of local RFI was eliminated, the results highlight the power of FAST in detecting extragalactic H i .
Publisher: American Astronomical Society
Date: 27-10-2015
Publisher: Oxford University Press (OUP)
Date: 12-2011
Publisher: Oxford University Press (OUP)
Date: 23-11-2017
Publisher: Oxford University Press (OUP)
Date: 20-06-2017
Publisher: BioResources
Date: 23-02-2018
Publisher: American Astronomical Society
Date: 15-10-2018
Publisher: Cambridge University Press (CUP)
Date: 2023
DOI: 10.1017/PASA.2023.28
Abstract: We investigate the ersity in the sizes and average surface densities of the neutral atomic hydrogen (H i ) gas discs in $\\sim$ 280 nearby galaxies detected by the Widefield ASKAP L-band Legacy All-sky Blind Survey (WALLABY). We combine the uniformly observed, interferometric H i data from pilot observations of the Hydra cluster and NGC 4636 group fields with photometry measured from ultraviolet, optical, and near-infrared imaging surveys to investigate the interplay between stellar structure, star formation, and H i structural parameters. We quantify the H i structure by the size of the H i relative to the optical disc and the average H i surface density measured using effective and isodensity radii. For galaxies resolved by $ $ $1.3$ beams, we find that galaxies with higher stellar masses and stellar surface densities tend to have less extended H i discs and lower H i surface densities: the isodensity H i structural parameters show a weak negative dependence on stellar mass and stellar mass surface density. These trends strengthen when we limit our s le to galaxies resolved by $ $ 2 beams. We find that galaxies with higher H i surface densities and more extended H i discs tend to be more star forming: the isodensity H i structural parameters have stronger correlations with star formation. Normalising the H i disc size by the optical effective radius (instead of the isophotal radius) produces positive correlations with stellar masses and stellar surface densities and removes the correlations with star formation. This is due to the effective and isodensity H i radii increasing with mass at similar rates while, in the optical, the effective radius increases slower than the isophotal radius. Our results are in qualitative agreement with previous studies and demonstrate that with WALLABY we can begin to bridge the gap between small galaxy s les with high spatial resolution H i data and large, statistical studies using spatially unresolved, single-dish data.
Publisher: Springer Science and Business Media LLC
Date: 25-10-2017
Publisher: College of Graduate Studies, Walailak University
Date: 15-01-2021
Abstract: The objective of this study was to investigate the most influenced levels of pressure and length of time on modulus of rupture (MOR) and modulus of elasticity (MOE) of teak laminated veneer lumber (LVL). Teak LVL was taken from the Faculty of Forestry’s forest plantation in Vientiane, Laos. The peeled veneer’s thickness was 2.3 mm. The veneer was air-dried until the moisture content reached the range of 6 to 10 %. Teak LVL panels were assembled from 9-ply panels of veneer using PL116- Liquid phenol-formaldehyde resin adhesive. The temperature was at 120 °C at 3 different pressure levels i.e., 1.5, 2 and 2.5 MPa and levels of time i.e. 9, 11 and 13 min. The experiment was conducted based on ISO16978. Intron Machine Model 5569 was used for the bending test of LVL with a dimension of 20×20×360 mm3. The bending test results on teak LVL showed significantly different MOR and MOE based on length of time and pressure levels of pressing.
Publisher: AIP
Date: 2010
DOI: 10.1063/1.3458573
Publisher: Springer Science and Business Media LLC
Date: 22-10-2019
Publisher: American Astronomical Society
Date: 30-12-2010
Publisher: Informa UK Limited
Date: 19-03-2018
Publisher: Oxford University Press (OUP)
Date: 09-03-2012
Publisher: Oxford University Press (OUP)
Date: 07-05-2021
Abstract: We characterize the conditional distributions of the H i gas-to-stellar mass ratio, $\\mbox{$R_{\\rm H\\,\\rm{i}}$}\\equiv \\mbox{$M_{\\rm H\\,\\rm{i}}$}/\\mbox{$M_{\\ast }$}$, given the stellar mass, M*, of local galaxies from M* ∼ 107–1012 M⊙ separated into centrals and satellites as well as into late- and early-type galaxies (LTGs and ETGs, respectively). To do so, we use (1) the homogeneous ‘eXtended GALEX Arecibo SDSS Survey’, xGASS (Catinella et al. 2018), by re-estimating their upper limits and taking into account them in our statistical analysis and (2) the results from a large compilation of H i data reported in Calette et al. (2018). We use the $R_{\\rm H\\,\\rm{i}}$ conditional distributions combined with the Galaxy Stellar Mass Function to infer the bivariate $M_{\\rm H\\,\\rm{i}}$ and M* distribution of all galaxies as well of the late/early-type and central/satellite subs les and their combinations. Satellites are on average less H i gas-rich than centrals at low and intermediate masses, with differences being larger for ETGs than LTGs at M* & 3−5 × 1010 M⊙ the differences are negligible. The differences in the H i gas content are much larger between LTGs and ETGs than between centrals and satellites. Our empirical H i Mass Function is strongly dominated by central galaxies at all masses. The empirically constrained bivariate $M_{\\rm H\\,\\rm{i}}$ and M* distributions presented here can be used to compare and constrain theoretical predictions as well as to generate galaxy mock catalogues.
Publisher: American Astronomical Society
Date: 30-09-2013
Publisher: Oxford University Press (OUP)
Date: 10-2006
Publisher: Oxford University Press (OUP)
Date: 21-12-2012
Publisher: Oxford University Press (OUP)
Date: 24-06-2011
Publisher: Springer Science and Business Media LLC
Date: 25-05-2022
Publisher: Oxford University Press (OUP)
Date: 24-06-2011
Publisher: Oxford University Press (OUP)
Date: 09-08-2021
Abstract: We present observations of the Eridanus supergroup obtained with the Australian Square Kilometre Array Pathfinder (ASKAP) as part of the pre-pilot survey for the Widefield ASKAP L-band Legacy All-sky Blind surveY (WALLABY). The total number of detected H i sources is 55, of which 12 are background galaxies not associated with the Eridanus supergroup. Two massive H i clouds are identified and large H i debris fields are seen in the NGC 1359 interacting galaxy pair, and the face-on spiral galaxy NGC 1385. We describe the data products from the source finding algorithm and present the basic parameters. The presence of distorted H i morphology in all detected galaxies suggests ongoing tidal interactions within the subgroups. The Eridanus group has a large fraction of H i-deficient galaxies as compared to previously studied galaxy groups. These H i-deficient galaxies are not found at the centre of the group. We find that galaxies in the Eridanus supergroup do not follow the general trend of the atomic gas fraction versus stellar mass scaling relation, which indicates that the scaling relation changes with environmental density. In general, the majority of these galaxies are actively forming stars.
Publisher: Oxford University Press (OUP)
Date: 12-01-2018
DOI: 10.1093/MNRAS/STY089
Publisher: American Astronomical Society
Date: 31-07-2007
DOI: 10.1086/521100
Publisher: BioResources
Date: 02-04-2018
Publisher: Oxford University Press (OUP)
Date: 25-07-2019
Abstract: Using a spectral stacking technique, we measure the neutral hydrogen (H i) properties of a s le of galaxies at z 0.11 across 35 pointings of the Westerbork Synthesis Radio Telescope. The radio data contain 1895 galaxies with redshifts and positions known from the Sloan Digital Sky Survey. We carefully quantified the effects of s le bias, aperture used to extract spectra, sidelobes and weighting technique and use our data to provide a new estimate for the cosmic H i mass density. We find a cosmic H i mass density of $\\Omega _{\\rm H\\,{\\small I}} = (4.02 \\pm 0.26)\\times 10^{-4} h_{70}^{-1}$ at 〈z〉 = 0.066, consistent with measurements from blind H i surveys and other H i stacking experiments at low redshifts. The combination of the small interferometer beam size and the large survey volume makes our result highly robust against systematic effects due to confusion at small scales and cosmic variance at large scales. Splitting into three sub-s les with 〈z〉 = 0.038, 0.067, and 0.093 shows no significant evolution of the H i gas content at low redshift.
Publisher: American Astronomical Society
Date: 04-02-2019
Publisher: Oxford University Press (OUP)
Date: 09-03-2018
DOI: 10.1093/MNRAS/STY242
Publisher: Oxford University Press (OUP)
Date: 14-07-2016
Publisher: Oxford University Press (OUP)
Date: 25-11-2020
Abstract: We examine how the post-processed content of molecular hydrogen (H2) in galaxies from the TNG100 cosmological, hydrodynamic simulation changes with environment at z = 0, assessing central/satellite status and host halo mass. We make close comparisons with the carbon monoxide (CO) emission survey xCOLD GASS where possible, having mock-observed TNG100 galaxies to match the survey’s specifications. For a representative s le of host haloes across 1011 ≲ M200c/M⊙ & 1014.6, TNG100 predicts that satellites with $m_* \\ge 10^9\\, {\\rm M}_{\\odot }$ should have a median deficit in their H2 fractions of ∼0.6 dex relative to centrals of the same stellar mass. Once observational and group-finding uncertainties are accounted for, the signature of this deficit decreases to ∼0.2 dex. Remarkably, we calculate a deficit in xCOLD GASS satellites’ H2 content relative to centrals of 0.2–0.3 dex, in line with our prediction. We further show that TNG100 and SDSS data exhibit continuous declines in the average star formation rates of galaxies at fixed stellar mass in denser environments, in quantitative agreement with each other. By tracking satellites from their moment of infall in TNG100, we directly show that atomic hydrogen (H i) is depleted at fractionally higher rates than H2 on average. Supporting this picture, we find that the H2/H i mass ratios of satellites are elevated relative to centrals in xCOLD GASS. We provide additional predictions for the effect of environment on H2 – both absolute and relative to H i – that can be tested with spectral stacking in future CO surveys.
Publisher: Oxford University Press (OUP)
Date: 23-11-2018
Publisher: American Astronomical Society
Date: 09-09-2008
DOI: 10.1086/592328
Publisher: Informa UK Limited
Date: 10-2018
Publisher: Oxford University Press (OUP)
Date: 11-12-2017
Publisher: American Astronomical Society
Date: 16-07-2009
Publisher: Oxford University Press (OUP)
Date: 18-07-2016
Publisher: Oxford University Press (OUP)
Date: 29-11-2010
Publisher: Cambridge University Press (CUP)
Date: 2022
DOI: 10.1017/PASA.2022.50
Abstract: We present WALLABY pilot data release 1, the first public release of H i pilot survey data from the Wide-field ASKAP L-band Legacy All-sky Blind Survey (WALLABY) on the Australian Square Kilometre Array Pathfinder. Phase 1 of the WALLABY pilot survey targeted three $60\\,\\mathrm{deg}^{2}$ regions on the sky in the direction of the Hydra and Norma galaxy clusters and the NGC 4636 galaxy group, covering the redshift range of $z \\lesssim 0.08$ . The source catalogue, images and spectra of nearly 600 extragalactic H i detections and kinematic models for 109 spatially resolved galaxies are available. As the pilot survey targeted regions containing nearby group and cluster environments, the median redshift of the s le of $z \\approx 0.014$ is relatively low compared to the full WALLABY survey. The median galaxy H i mass is $2.3 \\times 10^{9}\\,{\\rm M}_{{\\odot}}$ . The target noise level of $1.6\\,\\mathrm{mJy}$ per 30 ′′ beam and $18.5\\,\\mathrm{kHz}$ channel translates into a $5 \\sigma$ H i mass sensitivity for point sources of about $5.2 \\times 10^{8} \\, (D_{\\rm L} / \\mathrm{100\\,Mpc})^{2} \\, {\\rm M}_{{\\odot}}$ across 50 spectral channels ( ${\\approx} 200\\,\\mathrm{km \\, s}^{-1}$ ) and a $5 \\sigma$ H i column density sensitivity of about $8.6 \\times 10^{19} \\, (1 + z)^{4}\\,\\mathrm{cm}^{-2}$ across 5 channels ( ${\\approx} 20\\,\\mathrm{km \\, s}^{-1}$ ) for emission filling the 30 ′′ beam. As expected for a pilot survey, several technical issues and artefacts are still affecting the data quality. Most notably, there are systematic flux errors of up to several 10% caused by uncertainties about the exact size and shape of each of the primary beams as well as the presence of sidelobes due to the finite deconvolution threshold. In addition, artefacts such as residual continuum emission and bandpass ripples have affected some of the data. The pilot survey has been highly successful in uncovering such technical problems, most of which are expected to be addressed and rectified before the start of the full WALLABY survey.
Publisher: Springer Science and Business Media LLC
Date: 15-10-2022
Publisher: Oxford University Press (OUP)
Date: 30-01-2012
Publisher: Oxford University Press (OUP)
Date: 07-10-2022
Abstract: Misalignments between the rotation axis of stars and gas are an indication of external processes shaping galaxies throughout their evolution. Using observations of 3068 galaxies from the SAMI Galaxy Survey, we compute global kinematic position angles for 1445 objects with reliable kinematics and identify 169 (12 per cent) galaxies which show stellar-gas misalignments. Kinematically decoupled features are more prevalent in early-type assive galaxies compared to late-type/star-forming systems. Star formation is the main source of gas ionization in only 22 per cent of misaligned galaxies 17 per cent are Seyfert objects, while 61 per cent show Low-Ionization Nuclear Emission-line Region features. We identify the most probable physical cause of the kinematic decoupling and find that, while accretion-driven cases are dominant, for up to 8 per cent of our s le, the misalignment may be tracing outflowing gas. When considering only misalignments driven by accretion, the acquired gas is feeding active star formation in only ∼1/4 of cases. As a population, misaligned galaxies have higher Sérsic indices and lower stellar spin and specific star formation rates than appropriately matched s les of aligned systems. These results suggest that both morphology and star formation/gas content are significantly correlated with the prevalence and timescales of misalignments. Specifically, torques on misaligned gas discs are smaller for more centrally concentrated galaxies, while the newly accreted gas feels lower viscous drag forces in more gas-poor objects. Marginal evidence of star formation not being correlated with misalignment likelihood for late-type galaxies suggests that such morphologies in the nearby Universe might be the result of preferentially aligned accretion at higher redshifts.
Publisher: Oxford University Press (OUP)
Date: 15-09-2021
Abstract: The kinematic morphology–density relation of galaxies is normally attributed to a changing distribution of galaxy stellar masses with the local environment. However, earlier studies were largely focused on slow rotators the dynamical properties of the overall population in relation to environment have received less attention. We use the SAMI Galaxy Survey to investigate the dynamical properties of ∼1800 early and late-type galaxies with log (M⋆/M⊙) & 9.5 as a function of mean environmental overdensity (Σ5) and their rank within a group or cluster. By classifying galaxies into fast and slow rotators, at fixed stellar mass above log (M⋆/M⊙) & 10.5, we detect a higher fraction (∼3.4σ) of slow rotators for group and cluster centrals and satellites as compared to isolated-central galaxies. We find similar results when using Σ5 as a tracer for environment. Focusing on the fast-rotator population, we also detect a significant correlation between galaxy kinematics and their stellar mass as well as the environment they are in. Specifically, by using inclination-corrected or intrinsic $\\lambda _{R_{\\rm {e}}}$ values, we find that, at fixed mass, satellite galaxies on average have the lowest $\\lambda _{\\, R_{\\rm {e}},\\rm {intr}}$, isolated-central galaxies have the highest $\\lambda _{\\, R_{\\rm {e}},\\rm {intr}}$, and group and cluster centrals lie in between. Similarly, galaxies in high-density environments have lower mean $\\lambda _{\\, R_{\\rm {e}},\\rm {intr}}$ values as compared to galaxies at low environmental density. However, at fixed Σ5, the mean $\\lambda _{\\, R_{\\rm {e}},\\rm {intr}}$ differences for low and high-mass galaxies are of similar magnitude as when varying Σ5 ($\\Delta \\lambda _{\\, R_{\\rm {e}},\\rm {intr}} \\sim 0.05$, with σrandom = 0.025, and σsyst & 0.03). Our results demonstrate that after stellar mass, environment plays a significant role in the creation of slow rotators, while for fast rotators we also detect an independent, albeit smaller, impact of mass and environment on their kinematic properties.
Publisher: American Astronomical Society
Date: 13-04-2010
Publisher: American Astronomical Society
Date: 28-12-2018
Publisher: JMIR Publications Inc.
Date: 29-06-2016
DOI: 10.2196/RESPROT.5619
Publisher: Oxford University Press (OUP)
Date: 14-06-2018
Publisher: Oxford University Press (OUP)
Date: 09-2013
Publisher: Oxford University Press (OUP)
Date: 16-01-2018
DOI: 10.1093/MNRAS/STY127
Publisher: American Astronomical Society
Date: 09-2005
DOI: 10.1086/432543
Publisher: Oxford University Press (OUP)
Date: 20-12-2018
Publisher: American Astronomical Society
Date: 07-2021
Abstract: This study uses H i image data from the Widefield ASKAP L-band Legacy All-sky Blind surveY (WALLABY) pilot survey with the Australian Square Kilometre Array Pathfinder (ASKAP) telescope, covering the Hydra cluster out to 2.5 r 200 . We present the projected phase–space distribution of H i -detected galaxies in Hydra, and identify that nearly two-thirds of the galaxies within 1.25 r 200 may be in the early stages of ram pressure stripping. More than half of these may be only weakly stripped, with the ratio of strippable H i (i.e., where the galactic restoring force is lower than the ram pressure in the disk) mass fraction (over total H i mass) distributed uniformly below 90%. Consequently, the H i mass is expected to decrease by only a few 0.1 dex after the currently strippable portion of H i in these systems has been stripped. A more detailed look at the subset of galaxies that are spatially resolved by WALLABY observations shows that, while it typically takes less than 200 Myr for ram pressure stripping to remove the currently strippable portion of H i , it may take more than 600 Myr to significantly change the total H i mass. Our results provide new clues to understanding the different rates of H i depletion and star formation quenching in cluster galaxies.
Publisher: Oxford University Press (OUP)
Date: 08-09-2022
Abstract: We use a s le of 559 disc galaxies extracted from the eXtended GALEX Arecibo SDSS Survey to study the connection between baryonic angular momentum, mass, and atomic gas fraction in the local Universe. Baryonic angular momenta are determined by combining H i and H2 integrated profiles with 2D stellar mass surface density profiles. In line with previous work, we confirm that specific angular momentum and atomic gas fraction are tightly correlated, but we find a larger scatter than previously observed. This is most likely due to the wider range of galaxy properties covered by our s le. We compare our findings with the predictions of the analytical stability model developed by Obreschkow et al. and find that, while the model provides a very good first-order approximation for the connection between baryonic angular momentum, mass, and gas fraction, it does not fully match our data. Specifically, we find that at fixed baryonic mass, the dependence of specific angular momentum on gas fraction is significantly weaker, and at fixed gas fraction, the slope of the angular momentum versus mass relation is shallower than what was predicted by the model. The reasons behind this tension remain unclear, but we speculate that multiple factors may simultaneously play a role, all related to the fact that the model is not able to encapsulate the full ersity of galaxy properties in our s le.
Publisher: Oxford University Press (OUP)
Date: 27-04-2022
Abstract: The stellar surface density within the inner 1 kpc (Σ1) has become a popular tool for understanding the growth of galaxies and its connection with the quenching of star formation. The emerging picture suggests that building a central dense core is a necessary condition for quenching. However, it is not clear whether changes in Σ1 trace changes in stellar kinematics and the growth of dispersion-dominated bulges. In this paper, we combine imaging from the Sloan Digital Sky Survey with stellar kinematics from the Sydney-AAO Multi-object Integral-field unit and Mapping Nearby Galaxies at Apache Point Observatory surveys to quantify the correlation between Σ1 and the proxy for stellar spin parameter within one effective radius (λre) for 1599 nearby galaxies. We show that, on the star-forming main sequence and at fixed stellar mass, changes in Σ1 are mirrored by changes in λre. While forming stars, main-sequence galaxies remain rotationally-dominated systems, with their Σ1 increasing but their stellar spin staying either constant or slightly increasing. The picture changes below the main sequence, where Σ1 and λre are no longer correlated. Passive systems show a narrower range of Σ1, but a wider range of λre compared to star-forming galaxies. Our results indicate that, from a structural point of view, passive galaxies are a more heterogeneous population than star-forming systems, and may have followed a variety of evolutionary paths. This also suggests that, if dispersion-dominated bulges still grow significantly at z ∼ 0, this generally takes place during, or after, the quenching phase.
Publisher: Oxford University Press (OUP)
Date: 07-10-2019
Abstract: We present a structural decomposition analysis of the galaxies in the extended GALEX Arecibo SDSS Survey (xGASS) using (gri) images from the Sloan Digital Sky Survey. Utilizing the 2D Bayesian light profile fitting code ProFit, we fit single- and double-component models taking advantage of a robust Markov chain Monte Carlo optimization algorithm in which we assume a Sérsic profile for single-component models and a combination of a Sérsic bulge and near-exponential disc (0.5 ≤ n ≤ 1.5) for double-component models. We investigate the effect of bulges on the atomic hydrogen (H i) content in galaxies by revisiting the H i-to-stellar mass scaling relations with the bulge-to-total ratio measured in the ProFit decompositions. We show that, at both fixed total and disc stellar mass, more bulge-dominated galaxies have systematically lower H i masses, implying that bulge-dominated galaxies with large H i reservoirs are rare in the local Universe. We see similar trends when separating galaxies by a bulge-to-total ratio based either on luminosity or stellar mass, however, the trends are more evident with luminosity. Importantly, when controlling for both stellar mass and star formation rate, the separation of atomic gas content reduces to within 0.3 dex between galaxies of different bulge-to-total ratios. Our findings suggest that the presence of a photometric bulge has little effect on the global H i gas reservoirs of local galaxies.
Publisher: American Astronomical Society
Date: 11-02-2008
Publisher: EDP Sciences
Date: 27-07-2012
Publisher: Oxford University Press (OUP)
Date: 07-02-2019
DOI: 10.1093/MNRAS/STZ380
Publisher: Wiley
Date: 09-09-2021
Abstract: Being able to assign sex to in iduals and identify autosomal and sex‐linked scaffolds are essential in most population genomic analyses. Non‐model organisms often have genome assemblies at scaffold‐level and lack characterization of sex‐linked scaffolds. Previous methods to identify sex and sex‐linked scaffolds have relied on synteny between the non‐model organism and a closely related species or prior knowledge about the sex of the s les to identify sex‐linked scaffolds. In the latter case, the difference in depth of coverage between the autosomes and the sex chromosomes are used. Here, we present “sex assignment through coverage” (SATC), a method to assign sex to s les and identify sex‐linked scaffolds from next generation sequencing (NGS) data. The method works for species with a homogametic/heterogametic sex determination system and only requires a scaffold‐level reference assembly and s ling of both sexes with whole genome sequencing (WGS) data. We use the sequencing depth distribution across scaffolds to jointly identify: (i) male and female in iduals, and (ii) sex‐linked scaffolds. This is achieved through projecting the scaffold depths into a low‐dimensional space using principal component analysis (PCA) and subsequent Gaussian mixture clustering. We demonstrate the applicability of our method using data from five mammal species and a bird species complex. The method is freely available at opgenDK/SATC as R code and a graphical user interface (GUI).
Publisher: Oxford University Press (OUP)
Date: 03-2021
Abstract: Galaxy internal structure growth has long been accused of inhibiting star formation in disc galaxies. We investigate the potential physical connection between the growth of dispersion-supported stellar structures (e.g. classical bulges) and the position of galaxies on the star-forming main sequence at z ∼ 0. Combining the might of the SAMI and MaNGA galaxy surveys, we measure the λRe spin parameter for 3289 galaxies over $9.5 \\lt \\log M_{\\star } [\\rm {M}_{\\odot }] \\lt 12$. At all stellar masses, galaxies at the locus of the main sequence possess λRe values indicative of intrinsically flattened discs. However, above $\\log M_{\\star }[\\rm {M}_{\\odot }]\\sim 10.5$ where the main sequence starts bending, we find tantalizing evidence for an increase in the number of galaxies with dispersion-supported structures, perhaps suggesting a connection between bulges and the bending of the main sequence. Moving above the main sequence, we see no evidence of any change in the typical spin parameter in galaxies once gravitationally interacting systems are excluded from the s le. Similarly, up to 1 dex below the main sequence, λRe remains roughly constant and only at very high stellar masses ($\\log M_{\\star }[\\rm {M}_{\\odot }]\\gt 11$), do we see a rapid decrease in λRe once galaxies decline in star formation activity. If this trend is confirmed, it would be indicative of different quenching mechanisms acting on high- and low-mass galaxies. The results suggest that whilst a population of galaxies possessing some dispersion-supported structure is already present on the star-forming main sequence, further growth would be required after the galaxy has quenched to match the kinematic properties observed in passive galaxies at z ∼ 0.
Publisher: EDP Sciences
Date: 27-02-2023
DOI: 10.1051/0004-6361/202244718
Abstract: Aims. In this Virgo Environment Traced in CO (VERTICO) science paper, we aim to study how the star formation process depends on the galactic environment and gravitational interactions in the context of galaxy evolution. We explore the scaling relation between the star formation rate surface density (Σ SFR ) and the molecular gas surface density (Σ mol ), also known as the Kennicutt-Schmidt relation, in a subs le of Virgo cluster spiral galaxies. Methods. We used new Atacama Compact Array and Total Power (ACA+TP) observations from the VERTICO-Atacama Large Millimeter/submillimeter Array (ALMA) Large Program at 720 pc resolution to resolve the molecular gas content, as traced by the 12 CO (2 − 1) transition, across the disks of 37 spiral galaxies in the Virgo cluster. In combination with archival UV and IR observations used to determine the star formation rate (SFR), we estimated the parameters of the Kennicutt-Schmidt (KS) relation for the entire ensemble of galaxies, and within in idual galaxies. Results. We find the KS slope for the entire population to be N = 0.97 ± 0.07, with a characteristic molecular gas depletion time of 1.86 Gyr for our full s le, which is in agreement with previous work in isolated, nearby star-forming galaxies. In in idual galaxies, we find that the KS slope ranges between 0.69 and 1.40, and that typical star formation efficiencies of molecular gas can vary from galaxy to galaxy by a factor of ∼4. These galaxy-to-galaxy variations account for ∼0.20 dex in scatter in the ensemble KS relation, which is characterized by a 0.42 dex scatter. In addition, we find that the HI-deficient galaxies in the Virgo cluster show a steeper resolved KS relation and lower molecular gas efficiencies than HI-normal cluster galaxies. Conclusions. While the molecular gas content in galaxies residing in the Virgo cluster appears – to first order – to behave similarly to that in isolated galaxies, our VERTICO s le of galaxies shows that cluster environments play a key role in regulating star formation. The environmental mechanisms affecting the HI galaxy content also have a direct impact on the star formation efficiency of molecular gas in cluster galaxies, leading to longer depletion times in HI-deficient members.
Publisher: Oxford University Press (OUP)
Date: 03-07-2020
Abstract: We present a comparison of galaxy atomic and molecular gas properties in three recent cosmological hydrodynamic simulations, namely SIMBA, EAGLE, and IllustrisTNG, versus observations from z ∼ 0 to 2. These simulations all rely on similar subresolution prescriptions to model cold interstellar gas that they cannot represent directly, and qualitatively reproduce the observed z ≈ 0 H i and H2 mass functions (HIMFs and H2MFs, respectively), CO(1–0) luminosity functions (COLFs), and gas scaling relations versus stellar mass, specific star formation rate, and stellar surface density μ*, with some quantitative differences. To compare to the COLF, we apply an H2-to-CO conversion factor to the simulated galaxies based on their average molecular surface density and metallicity, yielding substantial variations in αCO and significant differences between models. Using this, predicted z = 0 COLFs agree better with data than predicted H2MFs. Out to z ∼ 2, EAGLE’s and SIMBA’s HIMFs and COLFs strongly increase, while IllustrisTNG’s HIMF declines and COLF evolves slowly. EAGLE and simba reproduce high-LCO(1–0) galaxies at z ∼ 1–2 as observed, owing partly to a median αCO(z = 2) ∼ 1 versus αCO(z = 0) ∼ 3. Examining H i, H2, and CO scaling relations, their trends with M* are broadly reproduced in all models, but EAGLE yields too little H i in green valley galaxies, IllustrisTNG and SIMBA overproduce cold gas in massive galaxies, and SIMBA overproduces molecular gas in small systems. Using SIMBA variants that exclude in idual active galactic nucleus (AGN) feedback modules, we find that SIMBA’s AGN jet feedback is primarily responsible by lowering cold gas contents from z ∼ 1 → 0 by suppressing cold gas in $M_*\\gtrsim 10^{10}{\\rm \\,M}_\\odot$ galaxies, while X-ray feedback suppresses the formation of high-μ* systems.
Publisher: Cambridge University Press (CUP)
Date: 06-2007
DOI: 10.1017/S1743921307014226
Abstract: We present 21 cm observations of 5×1 square degrees centered on the local Abell cluster 1367 obtained as part of the Arecibo Galaxy Environment Survey. This represents the first HI selected s le covering the core and the outskirts of a local cluster of galaxies. Combining the HI data with SDSS optical imaging we show that in HI selected s les follow scaling relations similar to the ones usually observed in optically selected s les. The most striking difference between HI and optically selected s les resides in their large scale distribution: while optical and X-ray observations trace the cluster potential very well, at radio wavelengths there is almost no evidence of the cluster presence.
Publisher: Oxford University Press (OUP)
Date: 11-07-2012
Publisher: Oxford University Press (OUP)
Date: 11-08-2021
Abstract: We use high-resolution ASKAP observations of galaxies in the Eridanus supergroup to study their H i, angular momentum, and star formation properties, as part of the WALLABY pre-pilot survey efforts. The Eridanus supergroup is composed of three sub-groups in the process of merging to form a cluster. The main focus of this study is the Eridanus (or NGC 1395) sub-group. The baryonic specific angular momentum – baryonic mass (jb−Mb) relation for the Eridanus galaxies is observed to be an unbroken power law of the form $j_{\\mathrm{b}} \\propto M_{\\mathrm{b}}^{0.57 \\pm 0.05}$, with a scatter of ∼0.10 ± 0.01 dex, consistent with previous works. We examine the relation between the atomic gas fraction, fatm, and the integrated atomic disc stability parameter q (the fatm−q relation), and find that the Eridanus galaxies deviate significantly from the relation owing to environmental processes such as tidal interactions and ram pressure affecting their H i gas. We find that a majority of the Eridanus galaxies are H i deficient compared to normal star-forming galaxies in the field. We also find that the star formation among the Eridanus galaxies may be suppressed owing to their environment, thus hinting at significant levels of pre-processing within the Eridanus sub-group, even before the galaxies have entered a cluster-like environment.
Publisher: American Astronomical Society
Date: 12-2005
DOI: 10.1086/497431
Publisher: EDP Sciences
Date: 04-2014
Publisher: Oxford University Press (OUP)
Date: 14-05-2018
Publisher: American Astronomical Society
Date: 12-2005
DOI: 10.1086/497432
Publisher: Oxford University Press (OUP)
Date: 24-07-2015
Publisher: EDP Sciences
Date: 04-2014
Publisher: Oxford University Press (OUP)
Date: 23-12-2016
Publisher: American Astronomical Society
Date: 10-2023
Publisher: Oxford University Press (OUP)
Date: 22-12-2019
Publisher: Oxford University Press (OUP)
Date: 29-01-2018
DOI: 10.1093/MNRAS/STY214
Publisher: Oxford University Press (OUP)
Date: 28-08-2021
Abstract: We apply a spectral stacking technique to Westerbork Synthesis Radio Telescope observations to measure the neutral atomic hydrogen content (H i) of nearby galaxies in and around galaxy groups at z & 0.11. Our s le includes 577 optically selected galaxies (120 isolated galaxies and 457 satellites) covering stellar masses between 1010 and 1011.5 M⊙, cross-matched with Yang’s group catalogue, with angular and redshift positions from the Sloan Digital Sky Survey. We find that the satellites in the centres of groups have lower H i masses at fixed stellar mass and morphology (characterized by the inverse concentration index) relative to those at larger radii. These trends persist for satellites in both high-mass ($M_{\\rm halo} \\gt 10^{13.5}\\, h^{-1}\\, \\mathrm{M}_{\\odot }$) and low-mass ($M_{\\rm halo} \\leqslant 10^{13.5}\\, h^{-1}\\, \\mathrm{M}_{\\odot }$) groups, but disappear if we only consider group members in low local density (Σ & 5 gal Mpc−2) environments. Similar trends are found for the specific star formation rate. Interestingly, we find that the radial trends of decreasing H i mass with decreasing group-centric radius extend beyond the group virial radius, as isolated galaxies close to larger groups lack H i compared with those located more than ∼3.0 R180 away from the centre of their nearest group. We also measure these trends in the late-type subs le and obtain similar results. Our results suggest that the H i reservoir of galaxies can be affected before galaxies become group satellites, indicating the existence of pre-processing in the infalling isolated galaxies.
Publisher: BioResources
Date: 15-10-2020
DOI: 10.15376/BIORES.15.4.9075-9087
Abstract: Timber cracking, drying stress residuals, and the change of moisture content profile were investigated during the drying of Tectona grandis boards in a conventional laboratory kiln. The study applied a technique that simulated solar kiln conditions using a conventional laboratory kiln to dry timber, based on Vientiane’s climatic conditions (Laos). The theoretical recharge and discharge model was used to generate the potential drying schedule for the Vientiane area then the drying schedule was mimicked in a conventional laboratory kiln. Timber cracking and drying stress residual were monitored and measured using Image J software, and the change of moisture content profile was determined, based on the oven dry method. Measured moisture content data were compared with the theoretical drying model. The results showed that teak boards, of 25 mm thick, had no cracking. The drying stress residual was 0.8 ± 0.3 mm with the maximum of 1.53 mm. The initial average moisture content of 62% decreased to 12% within 16 d, while the case and core moisture contents reached 12% and 14%, respectively. The drying model described the changes of moisture content profile during drying, with a maximal error of 5%.
Publisher: Oxford University Press (OUP)
Date: 04-12-2021
Abstract: We present results from our analysis of the Hydra I cluster observed in neutral atomic hydrogen (H i) as part of the Widefield ASKAP L-band Legacy All-sky Blind Survey (WALLABY). These WALLABY observations cover a 60-square-degree field of view with uniform sensitivity and a spatial resolution of 30 arcsec. We use these wide-field observations to investigate the effect of galaxy environment on H i gas removal and star formation quenching by comparing the properties of cluster, infall, and field galaxies extending up to ∼5R200 from the cluster centre. We find a sharp decrease in the H i-detected fraction of infalling galaxies at a projected distance of ∼1.5R200 from the cluster centre from $\\sim 85{{\\ \\rm per\\ cent}}$ to $\\sim 35{{\\ \\rm per\\ cent}}$. We see evidence for the environment removing gas from the outskirts of H i-detected cluster and infall galaxies through the decrease in the H i to r-band optical disc diameter ratio. These galaxies lie on the star-forming main sequence, indicating that gas removal is not yet affecting the inner star-forming discs and is limited to the galaxy outskirts. Although we do not detect galaxies undergoing galaxy-wide quenching, we do observe a reduction in recent star formation in the outer disc of cluster galaxies, which is likely due to the smaller gas reservoirs present beyond the optical radius in these galaxies. Stacking of H i non-detections with H i masses below $M_{\\rm {HI}}\\lesssim 10^{8.4}\\, \\rm {M}_{\\odot }$ will be required to probe the H i of galaxies undergoing quenching at distances ≳60 Mpc with WALLABY.
Publisher: American Astronomical Society
Date: 29-12-2012
Publisher: Oxford University Press (OUP)
Date: 03-01-2020
Abstract: We study the relation between the properties of the bulge/disc components and the H i mass fraction of galaxies. We find that at fixed stellar mass, disc colours are correlated with the H i mass fraction, while bulge colours are not. The lack of a correlation between the bulge colour and the H i mass fraction is regardless whether the bulges are pseudo, or whether the galaxies host bars or are interacting with a neighbour. There is no strong correlation between the colours of the discs and bulges either. These results suggest that the current total amount of H i is closely related to the formation of discs, but does not necessarily fuel the formation of (pseudo) bulges in an efficient way. We do not find evidence for the star formation in the discs to be quenched by the bulges.
Publisher: Cambridge University Press (CUP)
Date: 2021
DOI: 10.1017/PASA.2021.18
Abstract: One of the key open questions in extragalactic astronomy is what stops star formation in galaxies. While it is clear that the cold gas reservoir, which fuels the formation of new stars, must be affected first, how this happens and what are the dominant physical mechanisms involved is still a matter of debate. At least for satellite galaxies, it is generally accepted that internal processes alone cannot be responsible for fully quenching their star formation, but that environment should play an important, if not dominant, role. In nearby clusters, we see ex les of cold gas being removed from the star-forming discs of galaxies moving through the intracluster medium, but whether active stripping is widespread and/or necessary to halt star formation in satellites, or quenching is just a consequence of the inability of these galaxies to replenish their cold gas reservoirs, remains unclear. In this work, we review the current status of environmental studies of cold gas in star-forming satellites in the local Universe from an observational perspective, focusing on the evidence for a physical link between cold gas stripping and quenching of the star formation. We find that stripping of cold gas is ubiquitous in satellite galaxies in both group and cluster environments. While hydrodynamical mechanisms such as ram pressure are important, the emerging picture across the full range of dark matter halos and stellar masses is a complex one, where different physical mechanisms may act simultaneously and cannot always be easily separated. Most importantly, we show that stripping does not always lead to full quenching, as only a fraction of the cold gas reservoir might be affected at the first pericentre passage. We argue that this is a key point to reconcile apparent tensions between statistical and detailed analyses of satellite galaxies, as well as disagreements between various estimates of quenching timescales. We conclude by highlighting several outstanding questions where we expect to see substantial progress in the coming decades, thanks to the advent of the Square Kilometre Array and its precursors, as well as the next-generation optical and millimeter facilities.
Publisher: American Astronomical Society
Date: 12-06-2008
Publisher: Oxford University Press (OUP)
Date: 08-08-2016
Publisher: Springer Science and Business Media LLC
Date: 07-2020
Publisher: Oxford University Press (OUP)
Date: 17-01-2020
Abstract: We present an analysis of asymmetries in global H i spectra from the extended GALEX Arecibo SDSS Survey (xGASS), a stellar mass-selected and gas fraction-limited survey which is representative of the H i properties of galaxies in the local Universe. We demonstrate that the asymmetry in a H i spectrum is strongly linked to its signal-to-noise meaning that, contrary to what was done in previous works, asymmetry distributions for different s les cannot be compared at face value. We develop a method to account for noise-induced asymmetry and find that the typical galaxy detected by xGASS exhibits higher asymmetry than what can be attributed to noise alone, with 37 per cent of the s le showing asymmetry greater than 10 per cent at an 80 per cent confidence level. We find that asymmetric galaxies contain, on average, 29 per cent less H i mass compared to their symmetric counterparts matched in both stellar mass and signal-to-noise. We also present clear evidence that satellite galaxies, as a population, exhibit more asymmetric H i spectra than centrals and that group central galaxies show a slightly higher rate of H i asymmetries compared to isolated centrals. All these results support a scenario in which environmental processes, in particular those responsible for gas removal, are the dominant driver of asymmetry in xGASS.
Publisher: Springer Science and Business Media LLC
Date: 18-09-2014
Publisher: Oxford University Press (OUP)
Date: 15-10-2020
Abstract: Observations of the cold neutral atomic hydrogen (H i) in and around disc galaxies have revealed that spatial and kinematic asymmetries are common place, and are reflected in the global H i spectra. We use the TNG100 box from the IllustrisTNG suite of cosmological simulations to study the conditions under which these asymmetries may arise in current theoretical galaxy formation models. We find that more than 50 per cent of the s le has at least a 10 per cent difference in integrated flux between the high- and low-velocity half of the spectrum, thus the typical TNG100 galaxy has an H i profile that is not fully symmetric. We find that satellite galaxies are a more asymmetric population than centrals, consistent with observational results. Using halo mass as a proxy for environment, this trend appears to be driven by the satellite population within the virial radius of haloes more massive than 1013 M⊙, typical of medium/large groups. We show that, while the excess of H i asymmetry in group satellites is likely driven by ram pressure, the bulk of the asymmetric H i profiles observed in TNG100 are driven by physical processes able to affect both the central and satellite populations. Our results highlight how asymmetries are not driven solely by environment, and multiple physical processes can produce the same asymmetric shape in global H i spectra.
Publisher: Cambridge University Press (CUP)
Date: 06-2007
DOI: 10.1017/S1743921307014214
Abstract: We present results from a targeted survey undertaken with the 305m Arecibo radiotelescope to detect H I -line emission from disk galaxies at redshift z .16. Among other applications, this dataset will be used to study the evolution of disk scaling relations at intermediate redshifts. Compared to optical velocity widths, H I measurements s le a larger fraction of the disks, where the rotation curves are typically flat, and are not affected by slit smearing and misalignment or by aperture effects. Thus, in contrast to studies based on optical spectroscopy, this dataset allows for a direct comparison with the local Tully-Fisher relation that is technique independent.
Publisher: Oxford University Press (OUP)
Date: 07-12-2022
Abstract: We present SAMI-H i, a survey of the atomic hydrogen content of 296 galaxies with integral field spectroscopy available from the SAMI Galaxy Survey. The s le spans nearly 4 dex in stellar mass ($M_\\star = 10^{7.4}-10^{11.1}~ \\rm M_\\odot$), redshift z & 0.06, and includes new Arecibo observations of 153 galaxies, for which we release catalogues and H i spectra. We use these data to compare the rotational velocities obtained from optical and radio observations and to show how systematic differences affect the slope and scatter of the stellar-mass and baryonic Tully–Fisher relations. Specifically, we show that $\\rm H\\alpha$ rotational velocities measured in the inner parts of galaxies (1.3 effective radii in this work) systematically underestimate H i global measurements, with H i/$\\rm H\\alpha$ velocity ratios that increase at low stellar masses, where rotation curves are typically still rising and $\\rm H\\alpha$ measurements do not reach their plateau. As a result, the $\\rm H\\alpha$ stellar mass Tully–Fisher relation is steeper (when M⋆ is the independent variable) and has larger scatter than its H i counterpart. Interestingly, we confirm the presence of a small fraction of low-mass outliers of the $\\rm H\\alpha$ relation that are not present when H i velocity widths are used and are not explained by ‘aperture effects’. These appear to be highly disturbed systems for which $\\rm H\\alpha$ widths do not provide a reliable estimate of the rotational velocity. Our analysis reaffirms the importance of taking into account differences in velocity definitions as well as tracers used when interpreting offsets from the Tully–Fisher relation, at both low and high redshifts and when comparing with simulations.
Publisher: Cambridge University Press (CUP)
Date: 06-2007
DOI: 10.1017/S1743921307013890
Abstract: The Arecibo Galaxy Environment Survey is a blind neutral hydrogen survey using the ALFA multibeam receiver at Arecibo Observatory to reach unprecedented sensitivities in a number of selected fields in the local Universe. When completed the survey will cover 200 square degrees out to a distance of at least 270 Mpc. If a population of gas-rich dark galaxies exists, then this survey is in a prime position to uncover that population. So far 20 square degrees have been covered in the regions of Abell 1367, the Virgo Cluster, the NGC 7332/9 galaxy pair and the isolated galaxy NGC 1156. Over 200 sources have been found, including a number that have no obvious optical counterparts. We discuss here the potential of AGES for uncovering more such objects and the characteristics of the dark sources identified to date.
Publisher: American Astronomical Society
Date: 03-2022
Abstract: We study the tidal interaction of galaxies in the Eridanus supergroup, using H i data from the pre-pilot survey of the Widefield ASKAP L -band Legacy All-sky Blind surveY. We obtain optical photometric measurements and quantify the strength of tidal perturbation using a tidal parameter S sum . For low-mass galaxies of M * ≲ 10 9 M ⊙ , we find a dependence of decreasing H i to optical disk size ratio with increasing S sum , but no dependence of H i spectral line asymmetry with S sum . This is consistent with the behavior expected under tidal stripping. We confirm that the color profile shape and color gradient depend on the stellar mass, but there is an additional correlation of low-mass galaxies having their color gradients within 2 R 50 increasing with higher S sum . For these low-mass galaxies, the dependence of color gradients on S sum is driven by the color becoming progressively redder in the inner disk when tidal perturbations are stronger. For high-mass galaxies, there is no dependence of color gradients on S sum , and we find a marginal reddening throughout the disks with increasing S sum . Our result highlights tidal interaction as an important environmental effect in producing the faint end of the star formation suppressed sequence in galaxy groups.
Publisher: American Astronomical Society
Date: 12-2022
Abstract: We measure the molecular-to-atomic gas ratio, R mol , and the star formation rate (SFR) per unit molecular gas mass, SFE mol , in 38 nearby galaxies selected from the Virgo Environment Traced in CO (VERTICO) survey. We stack ALMA 12 CO ( J = 2−1) spectra coherently using H i velocities from the VIVA survey to detect faint CO emission out to galactocentric radii r gal ∼ 1.2 r 25 . We determine the scale lengths for the molecular and stellar components, finding a ∼3:5 relation compared to ∼1:1 in field galaxies, indicating that the CO emission is more centrally concentrated than the stars. We compute R mol as a function of different physical quantities. While the spatially resolved R mol on average decreases with increasing radius, we find that the mean molecular-to-atomic gas ratio within the stellar effective radius R e , R mol ( r R e ), shows a systematic increase with the level of H i , truncation and/or asymmetry (H I perturbation). Analysis of the molecular- and the atomic-to-stellar mass ratios within R e , R ⋆ mol ( r R e ) and R ⋆ atom ( r R e ) , shows that VERTICO galaxies have increasingly lower R ⋆ atom ( r R e ) for larger levels of H I perturbation (compared to field galaxies matched in stellar mass), but no significant change in R ⋆ m o l ( r R e ) . We also measure a clear systematic decrease of the SFE mol within R e , SFE mol ( r R e ), with increasingly perturbed H i . Therefore, compared to field galaxies from the field, VERTICO galaxies are more compact in CO emission in relation to their stellar distribution, but increasingly perturbed atomic gas increases their R mol and decreases the efficiency with which their molecular gas forms stars.
Publisher: Oxford University Press (OUP)
Date: 11-08-2009
Publisher: Cambridge University Press (CUP)
Date: 08-2006
DOI: 10.1017/S1743921306006338
Abstract: The Arecibo Galaxy Environments Survey (AGES) is a 2000-hour neutral hydrogen (H I ) survey using the new Arecibo L-band Feed Array (ALFA) multibeam instrument at Arecibo Observatory. It will cover 200 square degrees of sky, s ling a range of environments from the Local Void through to the Virgo Cluster with higher sensitivity, spatial resolution and velocity resolution than previous neutral hydrogen surveys.
Publisher: Oxford University Press (OUP)
Date: 10-08-2021
Abstract: We present the Australian Square Kilometre Array Pathfinder (ASKAP) WALLABY pre-pilot observations of two ‘dark’ H i sources (with H i masses of a few times 108 $\\rm {M}_\\odot$ and no known stellar counterpart) that reside within 363 kpc of NGC 1395, the most massive early-type galaxy in the Eridanus group of galaxies. We investigate whether these ‘dark’ H i sources have resulted from past tidal interactions or whether they are an extreme class of low surface brightness galaxies. Our results suggest that both scenarios are possible, and not mutually exclusive. The two ‘dark’ H i sources are compact, reside in relative isolation, and are more than 159 kpc away from their nearest H i-rich galaxy neighbour. Regardless of origin, the H i sizes and masses of both ‘dark’ H i sources are consistent with the H i size–mass relationship that is found in nearby low-mass galaxies, supporting the possibility that these H i sources are an extreme class of low surface brightness galaxies. We identified three analogues of candidate primordial ‘dark’ H i galaxies within the TNG100 cosmological, hydrodynamic simulation. All three model analogues are dark matter dominated, have assembled most of their mass 12–13 Gyr ago, and have not experienced much evolution until cluster infall 1–2 Gyr ago. Our WALLABY pre-pilot science results suggest that the upcoming large-area H i surveys will have a significant impact on our understanding of low surface brightness galaxies and the physical processes that shape them.
Publisher: Massachusetts Medical Society
Date: 27-04-2023
Publisher: American Astronomical Society
Date: 28-06-2022
Abstract: In this VERTICO early science paper we explore in detail how environmental mechanisms, identified in H i , affect the resolved properties of molecular gas reservoirs in cluster galaxies. The molecular gas is probed using ALMA ACA (+TP) observations of 12 CO(2–1) in 51 spiral galaxies in the Virgo cluster (of which 49 are detected), all of which are included in the VIVA H i survey. The s le spans a stellar mass range of 9 ≤ log M ⋆ / M ⊙ ≤ 11 . We study molecular gas radial profiles, isodensity radii, and surface densities as a function of galaxy H i deficiency and morphology. There is a weak correlation between global H i and H 2 deficiencies, and resolved properties of molecular gas correlate with H i deficiency: galaxies that have large H i deficiencies have relatively steep and truncated molecular gas radial profiles, which is due to the removal of low-surface-density molecular gas on the outskirts. Therefore, while the environmental mechanisms observed in H i also affect molecular gas reservoirs, there is only a moderate reduction of the total amount of molecular gas.
Publisher: American Astronomical Society
Date: 08-12-2017
Publisher: Oxford University Press (OUP)
Date: 02-09-2010
Publisher: Oxford University Press (OUP)
Date: 19-07-2017
Publisher: Oxford University Press (OUP)
Date: 24-05-2019
Abstract: We use data from the Sydney-AAO Multi-object Integral-field spectroscopy (SAMI) Galaxy Survey to study the dynamical scaling relation between galaxy stellar mass M∗ and the general kinematic parameter $S_K = \\sqrt{K V_{\\rm rot}^2 + \\sigma ^2}$ that combines rotation velocity Vrot and velocity dispersion σ. We show that the log M∗ – log SK relation: (1) is linear above limits set by properties of the s les and observations (2) has slightly different slope when derived from stellar or gas kinematic measurements (3) applies to both early-type and late-type galaxies and has smaller scatter than either the Tully–Fisher relation (log M∗ − log Vrot) for late types or the Faber–Jackson relation (log M∗ − log σ) for early types and (4) has scatter that is only weakly sensitive to the value of K, with minimum scatter for K in the range 0.4 and 0.7. We compare SK to the aperture second moment (the ‘aperture velocity dispersion’) measured from the integrated spectrum within a 3-arcsecond radius aperture ($\\sigma _{3^{\\prime \\prime }}$). We find that while SK and $\\sigma _{3^{\\prime \\prime }}$ are in general tightly correlated, the log M∗ − log SK relation has less scatter than the $\\log M_* - \\log \\sigma _{3^{\\prime \\prime }}$ relation.
Publisher: Oxford University Press (OUP)
Date: 19-02-2019
DOI: 10.1093/MNRAS/STZ485
Publisher: Oxford University Press (OUP)
Date: 22-02-2010
Publisher: Oxford University Press (OUP)
Date: 12-2021
Abstract: We present a detailed study of the stellar mass versus specific angular momentum (AM) relation (Fall relation) for a representative s le of 564 nearby galaxies in the eXtended GALEX Arecibo SDSS Survey (xGASS). We focus on the dependence of the Fall relation’s slope on galaxy type and the galaxy properties regulating its scatter. Stellar specific AM is determined by combining single-dish H i velocity widths and stellar mass profiles for all H i detections in the xGASS s le. At fixed morphology (or bulge-to-total ratio), we find that the power-law slope of the Fall relation is consistent with 2/3. However, when all galaxy types are combined, we recover a much shallower slope of ∼0.47. We show that this is a consequence of the change in galaxy morphology as a function of mass, highlighting that caution should be taken when using the slope of the Fall relation to constrain galaxy formation models without taking s le selection into account. We quantify the Fall relations scatter and show that H i gas fraction is the strongest correlated parameter for low stellar masses (Spearman correlation: ρs = 0.61), while the bulge-to-total ratio becomes slightly more dominant at higher masses (ρs = −0.29). Intriguingly, when only the disc components of galaxies are considered, H i gas fraction remains the strongest correlated parameter with the scatter of the relation (regardless of disc stellar mass). Our work provides one of the best characterizations of the Fall relation for a representative s le of galaxies in the local Universe.
Publisher: EDP Sciences
Date: 04-2021
DOI: 10.1051/0004-6361/202039803
Abstract: We present the first interferometric blind H I survey of the Fornax galaxy cluster, which covers an area of 15 deg 2 out to the cluster virial radius. The survey has a spatial and velocity resolution of 67″ × 95″(∼6 × 9 kpc at the Fornax cluster distance of 20 Mpc) and 6.6 km s −1 and a 3 σ sensitivity of N H I ∼ 2 × 10 19 cm −2 and M H I ∼ 2 × 10 7 M ⊙ , respectively. We detect 16 galaxies out of roughly 200 spectroscopically confirmed Fornax cluster members. The detections cover about three orders of magnitude in H I mass, from 8 × 10 6 to 1.5 × 10 10 M ⊙ . They avoid the central, virialised region of the cluster both on the sky and in projected phase-space, showing that they are recent arrivals and that, in Fornax, H I is lost within a crossing time, ∼2 Gyr. Half of these galaxies exhibit a disturbed H I morphology, including several cases of asymmetries, tails, offsets between H I and optical centres, and a case of a truncated H I disc. This suggests that these recent arrivals have been interacting with other galaxies, the large-scale potential or the intergalactic medium, within or on their way to Fornax. As a whole, our Fornax H I detections are H I -poorer and form stars at a lower rate than non-cluster galaxies in the same M ⋆ range. This is particularly evident at M ⋆ ≲ 10 9 M ⊙ , indicating that low mass galaxies are more strongly affected throughout their infall towards the cluster. The M H I / M ⋆ ratio of Fornax galaxies is comparable to that in the Virgo cluster . At fixed M ⋆ , our H I detections follow the non-cluster relation between M H I and the star formation rate, and we argue that this implies that thus far they have lost their H I on a timescale ≳1−2 Gyr. Deeper inside the cluster H I removal is likely to proceed faster, as confirmed by a population of H I -undetected but H 2 -detected star-forming galaxies. Overall, based on ALMA data, we find a large scatter in H 2 -to-H I mass ratio, with several galaxies showing an unusually high ratio that is probably caused by faster H I removal. Finally, we identify an H I -rich subgroup of possible interacting galaxies dominated by NGC 1365, where pre-processing is likely to have taken place.
Publisher: Oxford University Press (OUP)
Date: 20-05-2020
Abstract: We infer the intrinsic ionized gas kinematics for 383 star-forming galaxies across a range of integrated star formation rates (SFR ∈ [10−3, 102] M⊙ yr−1) at z ≲ 0.1 using a consistent 3D forward-modelling technique. The total s le is a combination of galaxies from the Sydney-AAO Multiobject Integral field Spectrograph (SAMI) Galaxy survey and DYnamics of Newly Assembled Massive Objects survey. For typical low-z galaxies taken from the SAMI Galaxy Survey, we find the vertical velocity dispersion (σv,z) to be positively correlated with measures of SFR, stellar mass, H i gas mass, and rotational velocity. The greatest correlation is with SFR surface density (ΣSFR). Using the total s le, we find σv,z increases slowly as a function of integrated SFR in the range SFR ∈ [10−3, 1] M⊙ yr−1 from 17 ± 3 to 24 ± 5 km s−1 followed by a steeper increase up to σv,z ∼80 km s−1 for SFR ≳ 1 M⊙ yr−1. This is consistent with recent theoretical models that suggest a σv,z floor driven by star formation feedback processes with an upturn in σv,z at higher SFR driven by gravitational transport of gas through the disc.
Publisher: Wiley
Date: 03-02-2023
DOI: 10.1111/MEC.16851
Abstract: The iconic Cape buffalo has experienced several documented population declines in recent history. These declines have been largely attributed to the late 19th century rinderpest pandemic. However, the effect of the rinderpest pandemic on their genetic ersity remains contentious, and other factors that have potentially affected this ersity include environmental changes during the Pleistocene, range expansions and recent human activity. Motivated by this, we present analyses of whole genome sequencing data from 59 in iduals from across the Cape buffalo range to assess present‐day levels of genome‐wide genetic ersity and what factors have influenced these levels. We found that the Cape buffalo has high average heterozygosity overall (0.40%), with the two southernmost populations having significantly lower heterozygosity levels (0.33% and 0.29%) on par with that of the domesticated water buffalo (0.29%). Interestingly, we found that these lower levels are probably due to recent inbreeding (average fraction of runs of homozygosity 23.7% and 19.9%) rather than factors further back in time during the Pleistocene. Moreover, detailed investigations of recent demographic history show that events across the past three centuries were the main drivers of the exceptional loss of genetic ersity in the southernmost populations, coincident with the onset of colonialism in the southern extreme of the Cape buffalo range. Hence, our results add to the growing body of studies suggesting that multiple recent human‐mediated impacts during the colonial period caused massive losses of large mammal abundance in southern Africa.
Publisher: Springer Science and Business Media LLC
Date: 30-10-2023
Publisher: Oxford University Press (OUP)
Date: 03-02-2020
Abstract: We use spectral stacking to measure the contribution of galaxies of different masses and in different hierarchies to the cosmic atomic hydrogen (H i) mass density in the local Universe. Our s le includes 1793 galaxies at z & 0.11 observed with the Westerbork Synthesis Radio Telescope, for which Sloan Digital Sky Survey spectroscopy and hierarchy information are also available. We find a cosmic H i mass density of $\\Omega _{\\rm H\\, \\small {I} } = (3.99 \\pm 0.54)\\times 10^{-4} \\, h_{70}^{-1}$ at 〈 z〉 = 0.065. For the central and satellite galaxies, we obtain $\\Omega _{\\rm H\\, {\\small {I}}}$ of $(3.51 \\pm 0.49)\\times 10^{-4} \\, h_{70}^{-1}$ and $(0.90 \\pm 0.16)\\times 10^{-4} \\, h_{70}^{-1}$, respectively. We show that galaxies above and below stellar masses of ∼109.3 M⊙ contribute in roughly equal measure to the global value of $\\Omega _{\\rm H\\, \\small {I} }$. While consistent with estimates based on targeted H i surveys, our results are in tension with previous theoretical work. We show that these differences are, at least partly, due to the empirical recipe used to set the partition between atomic and molecular hydrogen in semi-analytical models. Moreover, comparing our measurements with the cosmological semi-analytic models of galaxy formation Shark and GALFORM reveals gradual stripping of gas via ram pressure works better to fully reproduce the properties of satellite galaxies in our s le than strangulation. Our findings highlight the power of this approach in constraining theoretical models and confirm the non-negligible contribution of massive galaxies to the H i mass budget of the local Universe.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 07-2015
Publisher: Sissa Medialab
Date: 29-05-2015
DOI: 10.22323/1.215.0128
Publisher: American Astronomical Society
Date: 17-11-2017
Publisher: Springer Science and Business Media LLC
Date: 26-12-2022
Publisher: Oxford University Press (OUP)
Date: 02-2021
Abstract: We have entered a new era where integral-field spectroscopic surveys of galaxies are sufficiently large to adequately s le large-scale structure over a cosmologically significant volume. This was the primary design goal of the SAMI Galaxy Survey. Here, in Data Release 3, we release data for the full s le of 3068 unique galaxies observed. This includes the SAMI cluster s le of 888 unique galaxies for the first time. For each galaxy, there are two primary spectral cubes covering the blue (370–570 nm) and red (630–740 nm) optical wavelength ranges at spectral resolving power of R = 1808 and 4304, respectively. For each primary cube, we also provide three spatially binned spectral cubes and a set of standardized aperture spectra. For each galaxy, we include complete 2D maps from parametrized fitting to the emission-line and absorption-line spectral data. These maps provide information on the gas ionization and kinematics, stellar kinematics and populations, and more. All data are available online through Australian Astronomical Optics Data Central.
Publisher: American Astronomical Society
Date: 10-11-2021
Publisher: American Astronomical Society
Date: 17-08-2010
Publisher: EDP Sciences
Date: 07-2023
DOI: 10.1051/0004-6361/202346599
Abstract: We analyse cold-gas distributions in Virgo cluster galaxies using resolved observations of CO(2-1), which traces molecular hydrogen (H 2 ), and H I from the Virgo Environment Traced In CO (VERTICO) and VLA Imaging of Virgo in Atomic Gas (VIVA) surveys. From a theoretical perspective, it is expected that environmental processes in clusters will have a stronger influence on diffuse atomic gas compared to the relatively dense molecular gas component, and that these environmental perturbations can compress the cold interstellar medium in cluster galaxies, leading to elevated star formation. In this work we observationally test these predictions for star-forming satellite galaxies within the Virgo cluster. We ided our Virgo galaxy s le into H I -normal, H I -tailed, and H I -truncated classes and show, unsurprisingly, that the H I -tailed galaxies have the largest quantitative H I asymmetries. We also compared Virgo galaxies to a control s le of non-cluster galaxies and find that the former, on average, have H I asymmetries that are 40 ± 10% larger than the latter. There is less separation between control, H I -normal, H I -tailed, and H I -truncated galaxies in terms of H 2 asymmetries, and on average, Virgo galaxies have H 2 asymmetries that are only marginally (20 ± 10%) larger than the control s le. We find a weak correlation between H I and H 2 asymmetries over our entire s le, but a stronger correlation for the galaxies that are strongly impacted by environmental perturbations. Finally, we ided the discs of the H I -tailed Virgo galaxies into a leading half and trailing half according to the observed tail direction. We find evidence for excess molecular gas mass on the leading halves of the disc. This excess molecular gas is accompanied by an excess in the star formation rate such that the depletion time is, on average, unchanged.
Publisher: Cambridge University Press (CUP)
Date: 08-2006
DOI: 10.1017/S1743921306010283
Abstract: We present the first results of a targeted survey carried out with the 305m Arecibo radiotelescope to detect H I -line emission from disk galaxies at redshift z 0.16. We are using this s le to study the evolution of the zero point of the Tully-Fisher relation (TFR) for galaxies at intermediate redshifts. Compared to optical widths, H I measurements s le a larger fraction of the disks, where the rotation curves are typically flat, and are not affected by slit smearing and misalignment or by aperture effects. Thus, in contrast to studies based on optical spectroscopy, this dataset allows for a direct comparison with the local TFR that is technique independent.
Publisher: EDP Sciences
Date: 03-2020
DOI: 10.1051/0004-6361/201936556
Abstract: Context. This paper presents the analysis of optical integral field spectra for the H I eXtreme (H IX ) galaxy s le. H IX galaxies host at least 2.5 times more atomic gas (H I ) than expected from their optical R -band luminosity. Previous examination of their star formation activity and H I kinematics suggested that these galaxies stabilise their large H I discs (radii up to 94 kpc) against star formation due to their higher than average baryonic specific angular momentum. A comparison to semi-analytic models further showed that the elevated baryonic specific angular momentum is inherited from the high spin of the dark matter host. Aims. In this paper we now turn to the gas-phase metallicity as well as stellar and ionised gas kinematics in H IX galaxies to gain insights into recent accretion of metal-poor gas or recent mergers. Methods. We compare the stellar, ionised, and atomic gas kinematics, and examine the variation in the gas-phase metallicity throughout the stellar disc of H IX galaxies. Results. We find no indication for counter-rotation in any of the components, the central metallicities tend to be lower than average, but as low as expected for galaxies of similar H I mass. Metallicity gradients are comparable to other less H I -rich, local star forming galaxies. Conclusions. We conclude that H IX galaxies show no conclusive evidence for recent major accretion or merger events. Their overall lower metallicities are likely due to being hosted by high spin halos, which slows down their evolution and thus the enrichment of their interstellar medium.
Publisher: Oxford University Press (OUP)
Date: 26-05-2023
Abstract: We determine the atomic hydrogen (H i) to halo mass relation (HIHM) using Arecibo Legacy Fast ALFA survey H i data at the location of optically selected groups from the Galaxy And Mass Assembly (GAMA) survey. We make direct H i detections for 37 GAMA groups. Using H i group spectral stacking of 345 groups, we study the group H i content as a function of halo mass across a halo mass range of 1011–1014.7 M⊙. We also correct our results for Eddington bias. We find that the group H i mass generally rises as a function of halo mass from 1.3% of the halo mass at $10^{11.6} \\, \\text{M}_\\odot$ to 0.4% at $10^{13.7} \\, \\text{M}_\\odot$ with some indication of flattening towards the high-mass end. Despite the differences in optical survey limits, group catalogues, and halo mass estimation methods, our results are consistent with previous group H i-stacking studies. Our results are also consistent with mock observations from shark and IllustrisTNG.
Publisher: Oxford University Press (OUP)
Date: 24-08-2011
Publisher: Oxford University Press (OUP)
Date: 22-06-2017
Publisher: Oxford University Press (OUP)
Date: 31-10-2019
Abstract: We use the complete Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy Survey to determine the contribution of slow rotators, as well as different types of fast rotators, to the stellar mass function of galaxies in the local Universe. We use stellar kinematics not only to discriminate between fast and slow rotators, but also to distinguish between dynamically cold systems (i.e., consistent with intrinsic axis ratios .3) and systems including a prominent dispersion-supported bulge. We show that fast rotators account for more than $80\\%$ of the stellar mass budget of nearby galaxies, confirming that their number density overwhelms that of slow rotators at almost all masses from 109 to 1011.5M⊙. Most importantly, dynamically cold disks contribute to at least $25\\%$ of the stellar mass budget of the local Universe, significantly higher than what is estimated from visual morphology alone. For stellar masses up to 1010.5M⊙, this class makes up $ =30\\%$ of the galaxy population in each stellar mass bin. The fact that many galaxies that are visually classified as having two-components have stellar spin consistent with dynamically cold disks suggests that the inner component is either rotationally-dominated (e.g., bar, pseudo-bulge) or has little effect on the global stellar kinematics of galaxies.
Publisher: American Astronomical Society
Date: 05-2022
Abstract: In the local universe, OH megamasers (OHMs) are detected almost exclusively in infrared-luminous galaxies, with a prevalence that increases with IR luminosity, suggesting that they trace gas-rich galaxy mergers. Given the proximity of the rest frequencies of OH and the hyperfine transition of neutral atomic hydrogen (H i ), radio surveys to probe the cosmic evolution of H i in galaxies also offer exciting prospects for exploiting OHMs to probe the cosmic history of gas-rich mergers. Using observations for the Looking At the Distant Universe with the MeerKAT Array (LADUMA) deep H i survey, we report the first untargeted detection of an OHM at z 0.5, LADUMA J033046.20−275518.1 (nicknamed “Nkalakatha”). The host system, WISEA J033046.26−275518.3, is an infrared-luminous radio galaxy whose optical redshift z ≈ 0.52 confirms the MeerKAT emission-line detection as OH at a redshift z OH = 0.5225 ± 0.0001 rather than H i at lower redshift. The detected spectral line has 18.4 σ peak significance, a width of 459 ± 59 km s −1 , and an integrated luminosity of (6.31 ± 0.18 [statistical] ± 0.31 [systematic]) × 10 3 L ⊙ , placing it among the most luminous OHMs known. The galaxy’s far-infrared luminosity L FIR = (1.576 ±0.013) × 10 12 L ⊙ marks it as an ultraluminous infrared galaxy its ratio of OH and infrared luminosities is similar to those for lower-redshift OHMs. A comparison between optical and OH redshifts offers a slight indication of an OH outflow. This detection represents the first step toward a systematic exploitation of OHMs as a tracer of galaxy growth at high redshifts.
Publisher: AIP
Date: 2008
DOI: 10.1063/1.2973577
Publisher: EDP Sciences
Date: 05-2021
DOI: 10.1051/0004-6361/202038961
Abstract: Context. The xGASS and xCOLD GASS surveys have measured the atomic (H I ) and molecular gas (H 2 ) content of a large and representative s le of nearby galaxies (redshift range of 0.01 z 0.05). Methods. We present optical longslit spectra for a subset of the xGASS and xCOLD GASS galaxies to investigate the correlation between radial metallicity profiles and cold gas content. In addition to previous data, this paper presents new optical spectra for 27 galaxies in the stellar mass range of 9.0 ≤ log M ⋆ [ M ⊙ ] ≤10.0. Methods. The longslit spectra were taken along the major axis of the galaxies, allowing us to obtain radial profiles of the gas-phase oxygen abundance (12 + log(O/H)). The slope of a linear fit to these radial profiles is defined as the metallicity gradient. We investigated correlations between these gradients and global galaxy properties, such as star formation activity and gas content. In addition, we examined the correlation of local metallicity measurements and the global H I mass fraction. Results. We obtained two main results: (i) the local metallicity is correlated with the global H I mass fraction, which is in good agreement with previous results. A simple toy model suggests that this correlation points towards a ‘local gas regulator model’ (ii) the primary driver of metallicity gradients appears to be stellar mass surface density (as a proxy for morphology). Conclusions. This work comprises one of the few systematic observational studies of the influence of the cold gas on the chemical evolution of star-forming galaxies, as considered via metallicity gradients and local measurements of the gas-phase oxygen abundance. Our results suggest that local density and local H I mass fraction are drivers of chemical evolution and the gas-phase metallicity.
Publisher: American Astronomical Society
Date: 31-05-2007
DOI: 10.1086/518827
Publisher: Oxford University Press (OUP)
Date: 17-03-2020
Abstract: We use our catalogue of structural decomposition measurements for the extended GALEX Arecibo SDSS Survey (xGASS) to study the role of bulges both along and across the galaxy star-forming main sequence (SFMS). We show that the slope in the sSFR–M⋆ relation flattens by ∼0.1 dex per decade in M⋆ when re-normalizing specifice star formation rate (sSFR) by disc stellar mass instead of total stellar mass. However, recasting the sSFR–M⋆ relation into the framework of only disc-specific quantities shows that a residual trend remains against disc stellar mass with equivalent slope and comparable scatter to that of the total galaxy relation. This suggests that the residual declining slope of the SFMS is intrinsic to the disc components of galaxies. We further investigate the distribution of bulge-to-total ratios (B/T) as a function of distance from the SFMS (ΔSFRMS). At all stellar masses, the average B/T of local galaxies decreases monotonically with increasing ΔSFRMS. Contrary to previous works, we find that the upper envelope of the SFMS is not dominated by objects with a significant bulge component. This rules out a scenario in which, in the local Universe, objects with increased star formation activity are simultaneously experiencing a significant bulge growth. We suggest that much of the discrepancies between different works studying the role of bulges originate from differences in the methodology of structurally decomposing galaxies.
Publisher: Oxford University Press (OUP)
Date: 22-11-2018
Publisher: American Astronomical Society
Date: 27-09-2012
Publisher: Oxford University Press (OUP)
Date: 04-01-2008
Publisher: American Astronomical Society
Date: 10-2023
Publisher: Oxford University Press (OUP)
Date: 31-10-2017
Publisher: Oxford University Press (OUP)
Date: 09-2023
Publisher: American Astronomical Society
Date: 30-06-2014
Publisher: Elsevier BV
Date: 10-2022
DOI: 10.1016/J.CMI.2022.05.010
Abstract: We aim to identify the preoperative and perioperative risk factors associated with post-surgical Staphylococcus aureus prosthetic joint infections (PJI) and to develop and validate risk-scoring systems, to allow a better identification of high-risk patients for more efficient targeted interventions. We performed a multicenter matched case-control study of patients who underwent a primary hip and knee arthroplasty from 2014 to 2016. Two multivariable models by logistic regression were performed, one for the preoperative and one for perioperative variables predictive scores also were developed and validated in an external cohort. In total, 130 cases and 386 controls were included. The variables independently associated with S. aureus-PJI in the preoperative period were (adjusted OR 95% CI): body mass index >30 kg/m Predictive scores for S. aureus-PJI were developed and validated this information would be useful for implementation of specific preventive measures.
Start Date: 2012
End Date: 2016
Funder: Australian Research Council
View Funded ActivityStart Date: 2015
End Date: 2017
Funder: Australian Research Council
View Funded ActivityStart Date: 2019
End Date: 2019
Funder: Australian Research Council
View Funded ActivityStart Date: 2015
End Date: 09-2018
Amount: $325,500.00
Funder: Australian Research Council
View Funded ActivityStart Date: 06-2013
End Date: 12-2017
Amount: $587,472.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2019
End Date: 12-2021
Amount: $656,639.00
Funder: Australian Research Council
View Funded ActivityStart Date: 07-2017
End Date: 12-2024
Amount: $30,300,000.00
Funder: Australian Research Council
View Funded Activity