ORCID Profile
0000-0003-4844-8659
Current Organisations
University of Western Australia
,
Australian SKA Regional Centre
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Publisher: Oxford University Press (OUP)
Date: 06-2019
Abstract: We present an H i study of the galaxy group LGG 351 using Widefield ASKAP L-band Legacy All-sky Blind Survey (WALLABY) early science data observed with the Australian Square Kilometre Array Pathfinder (ASKAP). LGG 351 resides behind the M 83 group at a velocity range (cz) of ∼3500–4800 km s−1 within the rich Hydra-Centaurus overdensity region. We detect 40 sources with the discovery of a tidally interacting galaxy pair and two new H i sources that are not presented in previous optical catalogues. 23 out of 40 sources have new redshifts derived from the new H i data. This study is the largest WALLABY sub-s le to date and also allows us to further validate the performance of ASKAP and the data reduction pipeline askapsoft. Extended H i emission is seen in six galaxies indicating interaction within the group, although no H i debris is found. We also detect H i in a known ultra-faint dwarf galaxy (dw 1328−29), which demonstrates that it is not a satellite of the M 83 group as previously thought. In conjunction with multiwavelength data, we find that our galaxies follow the atomic gas fraction and baryonic Tully–Fisher scaling relations derived from the GALEX Arecibo SDSS Survey. In addition, majority of our galaxies fall within the star formation main sequence indicating inefficiency of gas removal processes in this loose galaxy group.
Publisher: Oxford University Press (OUP)
Date: 12-11-2023
Abstract: The WALLABY pilot survey has been conducted using the Australian SKA Pathfinder (ASKAP). The integrated 21-cm H i line spectra are formed in a very different manner compared to usual single-dish spectra Tully–Fisher measurements. It is thus extremely important to ensure that slight differences (e.g. biases due to missing flux) are quantified and understood in order to maximise the use of the large amount of data becoming available soon. This article is based on four fields for which the data are scientifically interesting by themselves. The pilot data discussed here consist of 614 galaxy spectra at a rest wavelength of 21 cm. Of these spectra, 472 are of high enough quality to be used to potentially derive distances using the Tully–Fisher relation. We further restrict the s le to the 251 galaxies whose inclination is sufficiently close to edge-on. For these, we derive Tully–Fisher distances using the deprojected WALLABY velocity widths combined with infrared (WISE W1) magnitudes. The resulting Tully–Fisher distances for the Eridanus, Hydra, Norma, and NGC4636 clusters are 21.5, 53.5, 69.4, and 23.0 Mpc, respectively, with uncertainties of 5–10 per cent, which are better or equivalent to the ones obtained in studies using data obtained with giant single dish telescopes. The pilot survey data show the benefits of WALLABY over previous giant single-dish telescope surveys. WALLABY is expected to detect around half a million galaxies with a mean redshift of $z = 0.05 (200\\, \\mathrm{Mpc})$. This study suggests that about 200 000 Tully–Fisher distances might result from the survey.
Publisher: CSIRO Publishing
Date: 03-08-2022
DOI: 10.1071/SH22101
Abstract: Background Recent changes to Australian PrEP prescribing guidelines support the use of event-driven pre-exposure prophylaxis (ED-PrEP) to prevent HIV among gay and bisexual men (GBM). Social marketing c aigns to increase awareness of ED-PrEP were conducted in early 2021. This study aimed to assess the awareness and knowledge of this method after these c aigns. Methods We conducted a national cross-sectional online survey about PrEP knowledge and attitudes from March to May 2021. Participants were asked if they had heard of ED-PrEP. Among aware participants, questions about the ‘2-1-1’ method were asked to assess knowledge. Bivariate and multivariate logistic regression analyses were conducted to assess the characteristics of those who were aware of ED-PrEP, and those who had correct knowledge of ED-PrEP. Analysis was restricted to non-HIV-positive cis-GBM who were aware of PrEP. Results Among the 419 participants eligible for this analysis, 286 (68.3%) had heard of ED-PrEP. Awareness was associated with living in a postcode with ≥10% gay men, PrEP experience, and belief ED-PrEP is effective. Of these 286 participants, 125 (43.7%) correctly answered questions about how to take ED-PrEP. Correct knowledge was associated with PrEP experience and belief ED-PrEP is effective. Conclusions A growing proportion of GBM are aware of ED-PrEP, but many still do not know how to take it as per clinical guidelines. More work is needed to increase knowledge among GBM to promote effective use of this method.
Publisher: Springer Science and Business Media LLC
Date: 2022
DOI: 10.1007/S10508-021-02276-2
Abstract: We examined depression and anxiety prior to and during COVID-19 restrictions in Australian gay and bisexual men (GBM). In an online cohort, a COVID-19-focused survey was conducted in April 2020. During 2019 and in April 2020, 664 GBM completed the Patient Health Questionnaire (PHQ-9, measuring depression) and Generalized Anxiety Disorder Assessment (GAD-7, measuring anxiety). Increased depression and anxiety were defined as a ≥ 5 point increase on the respective scales. Mean PHQ-9 and GAD-7 scores increased between 2019 and 2020 (PHQ-9: from 5.11 in 2019 to 6.55 in 2020 GAD-7: from 3.80 in 2019 to 4.95 in 2020). The proportion of participants with moderate-severe depression (PHQ-9 ≥ 10) increased from 18.8% ( n = 125) to 25.5% ( n = 169), while the proportion of participants with moderate-severe anxiety (GAD-7 ≥ 10) increased from 12.7% ( n = 84) to 17.3% ( n = 115). Almost one-quarter of participants ( n = 158, 23.8%) had increased depression in these men, mean PHQ-9 increased from 2.49 in 2019 to 11.65 in 2020 ( p 0.001). One-in-five (20.6%) participants ( n = 137) had increased anxiety among these men, mean GAD-7 increased from 2.05 in 2019 to 10.22 in 2020 ( p 0.001). Increases were associated with concerns about job security, reduction in social and sexual connections and opportunities, and being personally concerned about COVID-19 itself. COVID-19 appeared to have a sudden and pronounced impact on depression and anxiety in Australian GBM, with a significant minority showing sharp increases. Ongoing monitoring is required to determine longer-term impacts and GBM need access to appropriate and sensitive supports both during and after the COVID-19 pandemic.
Publisher: Springer Science and Business Media LLC
Date: 27-07-2022
DOI: 10.1007/S10461-022-03788-1
Abstract: COVID-19 has disrupted sexual behaviour and access to health systems. We adapted regular HIV behavioural surveillance of gay and bisexual men (GBM) in Australia in response to COVID-19, assessed the impact on the profile of the s le, the participants’ HIV-related behaviour, and whether COVID-19 may have accentuated existing disparities in the Australian HIV epidemic. Data collected from five states during July 2017–June 2021 were included (N = 31,460). The emphasis on online recruitment after COVID-19 led to smaller s le sizes, greater geographic reach, and a higher proportion of bisexual-identifying participants. Most participants (88.1%) reported physical distancing and 52.1% had fewer sex partners due to COVID-19. In the COVID-19-affected rounds (July 2020–June 2021), the number of male partners, recent HIV testing and pre-exposure prophylaxis (PrEP) use all fell, and HIV risk among the smaller group of participants who reported casual sex increased. COVID-related changes were generally more pronounced among GBM aged under 25 years, participants from suburbs with fewer gay residents, and bisexual men. These groups should be prioritised when encouraging GBM to reengage with HIV testing services and effective prevention methods, like condoms and PrEP.
Publisher: Cambridge University Press (CUP)
Date: 03-2016
DOI: 10.1017/S1743921316009066
Abstract: We present the results of a multi-wavelength investigation of the dwarf galaxy populations in three interacting galaxy groups: NGC 871/6/7, NGC 3166/9, NGC 4725/47. Using degree-scale Giant Metrewave Radio Telescope H i mosaics and deep optical photometry from the Canada-France-Hawaii Telescope, we measured the H i and stellar properties of the gas-rich low-mass group members to classify each one as a classical dwarf galaxy, a short-lived tidal knot or a tidal dwarf galaxy (TDG). Our observations detect several dwarf irregulars and various tidal knots. We identify four potentially long-lived tidal objects in the three groups, implying that TDGs are not readily produced. The tidal objects examined in this small survey also appear to have a wider variety of properties than TDGs formed in current simulations.
Publisher: Zenodo
Date: 2020
Publisher: Oxford University Press (OUP)
Date: 26-07-2019
Abstract: We present a Wide-field ASKAP L-Band Legacy All-sky Blind surveY (WALLABY) study of the nearby (vsys = 915 km s−1) spiral galaxy IC 5201 using the Australian Square Kilometre Array Pathfinder (ASKAP). IC 5201 is a blue, barred spiral galaxy that follows the known scaling relations between stellar mass, SFR, H i mass, and diameter. We create a four-beam mosaicked H i image cube from 175 h of observations made with a 12-antenna sub-array. The root mean square noise level of the cube is 1.7 mJy beam−1 per channel, equivalent to a column density of $N_{\\rm H\\, \\small {I}}$ = 1.4 × 1020 cm−2 over 25 km s−1. We report nine extragalactic H i detections – five new H i detections including the first velocity measurements for two galaxies. These sources are IC 5201, three dwarf satellite galaxies, two galaxies, and a tidal feature belonging to the NGC 7232/3 triplet and two potential infalling galaxies to the triplet. There is evidence of a previous tidal interaction between IC 5201 and the irregular satellite AM 2220−460. A close fly-by is likely responsible for the asymmetric optical morphology of IC 5201 and warping its disc, resulting in the irregular morphology of AM 2220−460. We quantify the H i kinematics of IC 5201, presenting its rotation curve as well as showing that the warp starts at 14 kpc along the major axis, increasing as a function of radius with a maximum difference in position angle of 20°. There is no evidence of stripped H i, triggered or quenched star formation in the system as measured using DECam optical and GALEX UV photometry.
Publisher: Springer Science and Business Media LLC
Date: 17-06-2022
DOI: 10.1007/S10461-021-03344-3
Abstract: Alternatives to daily dosing of HIV pre-exposure prophylaxis (PrEP) are continuing to emerge. From October 2019 to March 2020, we conducted an online survey of PrEP-experienced gay and bisexual men in Australia about interest in and preference for four different PrEP modalities: daily dosing, event-driven dosing, long-acting injectable (LAI)-PrEP and subdermal PrEP implants. Using data from 1477 participants, we measured interest and preference of different modalities using multivariate logistic regression. High proportions of participants were interested in LAI-PrEP (59.7%), daily PrEP (52.0%), PrEP implants (45.3%) and event-driven PrEP (42.8%). LAI-PrEP was the most frequently selected preference (30.5%), followed by PrEP implants (26.3%), daily PrEP (21.4%) and event-driven PrEP (21.2%). Higher interest and preference for non-daily PrEP modalities were associated with being concerned about side effects and perceived difficulties with daily adherence. As novel modalities emerge, attitudes to them should be considered in public health messaging to facilitate informed decision-making.
Publisher: American Astronomical Society
Date: 05-2023
Abstract: We report on the commensal ASKAP detection of a fast radio burst (FRB), FRB 20211127I, and the detection of neutral hydrogen (H i ) emission in the FRB host galaxy, WALLABY J131913–185018 (hereafter W13–18). This collaboration between the CRAFT and WALLABY survey teams marks the fifth, and most distant, FRB host galaxy detected in H i , not including the Milky Way. We find that W13–18 has an H i mass of M HI = 6.5 × 10 9 M ⊙ , an H i -to-stellar mass ratio of 2.17, and coincides with a continuum radio source of flux density at 1.4 GHz of 1.3 mJy. The H i global spectrum of W13–18 appears to be asymmetric, albeit the H i observation has a low signal-to-noise ratio (S/N), and the galaxy itself appears modestly undisturbed. These properties are compared to the early literature of H i emission detected in other FRB hosts to date, where either the H i global spectra were strongly asymmetric, or there were clearly disrupted H i intensity map distributions. W13–18 lacks a sufficient S/N to determine whether it is significantly less asymmetric in its H i distribution than previous ex les of FRB host galaxies. However, there are no strong signs of a major interaction in the optical image of the host galaxy that would stimulate a burst of star formation and hence the production of putative FRB progenitors related to massive stars and their compact remnants.
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: Sissa Medialab
Date: 05-08-2015
DOI: 10.22323/1.250.0009
Publisher: Oxford University Press (OUP)
Date: 29-10-2019
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: American Astronomical Society
Date: 10-2023
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: 27-09-2023
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: Cambridge University Press (CUP)
Date: 2023
DOI: 10.1017/PASA.2023.11
Abstract: We present the highest resolution and sensitivity $\\sim$ $1.4\\,$ GHz continuum observations of the Eridanus supergroup obtained as a part of the Widefield Australian Square Kilometer Array Pathfinder (ASKAP) L -band Legacy All-sky Blind surveY (WALLABY) pre-pilot observations using the ASKAP. We detect 9461 sources at 1.37 GHz down to a flux density limit of $\\sim$ $0.1$ mJy at $6.1''\\times 7.9''$ resolution with a median root mean square of 0.05 mJy beam $^{-1}$ . We find that the flux scale is accurate to within 5 % (compared to NVSS at 1.4 GHz). We then determine the global properties of eight Eridanus supergroup members, which are detected in both radio continuum and neutral hydrogen (HI) emission, and find that the radio-derived star formation rates (SFRs) agree well with previous literature. Using our global and resolved radio continuum properties of the nearby Eridanus galaxies, we measure and extend the infrared-radio correlation (IRRC) to lower stellar masses and inferred SFRs than before. We find the resolved IRRC to be useful for: (1) discriminating between active galactic nuclei and star-forming galaxies (2) identifying background radio sources and (3) tracing the effects of group environment pre-processing in NGC 1385. We find evidence for tidal interactions and ram-pressure stripping in the HI, resolved spectral index and IRRC morphologies of NGC 1385. There appears to be a spatial coincidence (in projection) of double-lobed radio jets with the central HI hole of NGC 1367. The destruction of polycyclic aromatic hydrocarbons by merger-induced shocks may be driving the observed WISE W3 deficit observed in NGC 1359. Our results suggest that resolved radio continuum and IRRC studies are excellent tracers of the physical processes that drive galaxy evolution and will be possible on larger s le of sources with upcoming ASKAP radio continuum surveys.
Publisher: UNSWorks, UNSW
Date: 2020
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: 22-05-2017
Publisher: Springer Science and Business Media LLC
Date: 07-2020
Publisher: Oxford University Press (OUP)
Date: 27-05-2019
Abstract: This paper reports on the atomic hydrogen gas (H i) observations of the spiral galaxy NGC 1566 using the newly commissioned Australian Square Kilometre Array Pathfinder radio telescope. We measure an integrated H i flux density of $180.2$ Jy km s−1 emanating from this galaxy, which translates to an H i mass of $1.94\\times 10^{10}\\, \\mathrm{ M}_{\\odot }$ at an assumed distance of $21.3$ Mpc. Our observations show that NGC 1566 has an asymmetric and mildly warped H i disc. The H i-to-stellar mass fraction (M$_{\\rm{H\\,{{\\small I}}}}$/M∗) of NGC 1566 is 0.29, which is high in comparison with galaxies that have the same stellar mass ($10^{10.8}$ M⊙). We also derive the rotation curve of this galaxy to a radius of $50$ kpc and fit different mass models to it. The NFW, Burkert, and pseudo-isothermal dark matter halo profiles fit the observed rotation curve reasonably well and recover dark matter fractions of 0.62, 0.58, and 0.66, respectively. Down to the column density sensitivity of our observations ($N_{\\rm{H\\,{{\\small I}}}}\\, =\\, 3.7\\times 10^{19}$ cm−2), we detect no H i clouds connected to, or in the nearby vicinity of, the H i disc of NGC 1566 nor nearby interacting systems. We conclude that, based on a simple analytic model, ram pressure interactions with the IGM can affect the H i disc of NGC 1566 and is possibly the reason for the asymmetries seen in the H i morphology of NGC 1566.
Publisher: Cambridge University Press (CUP)
Date: 2022
DOI: 10.1017/PASA.2021.59
Abstract: We present the most sensitive and detailed view of the neutral hydrogen ( ${\\rm H\\small I}$ ) emission associated with the Small Magellanic Cloud (SMC), through the combination of data from the Australian Square Kilometre Array Pathfinder (ASKAP) and Parkes (Murriyang), as part of the Galactic Australian Square Kilometre Array Pathfinder (GASKAP) pilot survey. These GASKAP-HI pilot observations, for the first time, reveal ${\\rm H\\small I}$ in the SMC on similar physical scales as other important tracers of the interstellar medium, such as molecular gas and dust. The resultant image cube possesses an rms noise level of 1.1 K ( $1.6\\,\\mathrm{mJy\\ beam}^{-1}$ ) $\\mathrm{per}\\ 0.98\\,\\mathrm{km\\ s}^{-1}$ spectral channel with an angular resolution of $30^{\\prime\\prime}$ ( ${\\sim}10\\,\\mathrm{pc}$ ). We discuss the calibration scheme and the custom imaging pipeline that utilises a joint deconvolution approach, efficiently distributed across a computing cluster, to accurately recover the emission extending across the entire ${\\sim}25\\,\\mathrm{deg}^2$ field-of-view. We provide an overview of the data products and characterise several aspects including the noise properties as a function of angular resolution and the represented spatial scales by deriving the global transfer function over the full spectral range. A preliminary spatial power spectrum analysis on in idual spectral channels reveals that the power law nature of the density distribution extends down to scales of 10 pc. We highlight the scientific potential of these data by comparing the properties of an outflowing high-velocity cloud with previous ASKAP+Parkes ${\\rm H\\small I}$ test observations.
Publisher: Oxford University Press (OUP)
Date: 09-08-2014
Publisher: UNSW Centre for Social Research in Health, Sydney
Date: 2021
DOI: 10.26190/DTWE-JH83
Publisher: Springer Science and Business Media LLC
Date: 07-06-2022
DOI: 10.1007/S10508-022-02310-X
Abstract: Changes to how gay, bisexual, and other men who have sex with men (GBM) connect with each other and with their communities have implications for HIV prevention. Social engagement with gay men (defined as having friends who are gay men and spending time with them) has been associated with HIV related outcomes over time among Australian GBM. Using data collected in national, repeated, cross-sectional surveys of GBM between 1998 and 2020 ( N = 161,117), analyses of trends in the prevalence of gay social engagement (GSE) in Australia were conducted using linear regression. To assess changing associations with GSE at different time points in the HIV epidemic, three cross-sectional analyses were conducted on factors associated with high and low GSE in 1999/2000, 2009/2010, and 2019/2020 using bivariate and multivariable logistic regression. GSE (scored from 0 to 7) declined among all participants from 4.76 in 1998 to 4.04 in 2020 ( p 0.001) with a steeper decline among GBM aged under 25 years from 4.63 in 1998 to 3.40 in 2020 ( p 0.001). In all timepoints, high GSE was associated with older age, being university educated, full time employment, identifying as gay, recent HIV testing, and PrEP uptake. While mostly associated with protective behaviors, high GSE was also associated with some practices that may put GBM at risk of HIV infection such as drug-enhanced sex and group sex in the most recent timepoint. Changing levels of GSE have implications for health promotion among GBM, particularly how to engage GBM less connected to gay social networks.
Publisher: UNSW Centre for Social Research in Health, Sydney
Date: 2020
Publisher: American Astronomical Society
Date: 02-03-2015
Publisher: Oxford University Press (OUP)
Date: 20-11-2012
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: 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: UNSWorks, UNSW
Date: 2020
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: UNSWorks, UNSW
Date: 2022
DOI: 10.26190/P2GH-N362
Publisher: Centre for Social Research in Health, UNSW Sydney, Sydney
Date: 2019
Publisher: Oxford University Press (OUP)
Date: 30-11-2019
Publisher: Oxford University Press (OUP)
Date: 26-10-2022
Abstract: We present early science results from Deep Investigation of Neutral Gas Origins (DINGO), an $\\rm H$i survey using the Australian Square Kilometre Array Pathfinder (ASKAP). Using ASKAP subarrays available during its commissioning phase, DINGO early science data were taken over ∼60 deg2 of the Galaxy And Mass Assembly (GAMA) 23 h region with 35.5 h integration time. We make direct detections of six known and one new sources at z & 0.01. Using $\\rm H$ i spectral stacking, we investigate the $\\rm H$ i gas content of galaxies at 0.04 & z & 0.09 for different galaxy colours. The results show that galaxy morphology based on optical colour is strongly linked to $\\rm H$ i gas properties. To examine environmental impacts on the $\\rm H$i gas content of galaxies, three subs les are made based on the GAMA group catalogue. The average $\\rm H$i mass of group central galaxies is larger than those of satellite and isolated galaxies, but with a lower $\\rm H$i gas fraction. We derive a variety of $\\rm H$i scaling relations for physical properties of our s le, including stellar mass, stellar mass surface density, NUV − r colour, specific star formation rate, and halo mass. We find that the derived $\\rm H$i scaling relations are comparable to other published results, with consistent trends also observed to ∼0.5 dex lower limits in stellar mass and stellar surface density. The cosmic $\\rm H$i densities derived from our data are consistent with other published values at similar redshifts. DINGO early science highlights the power of $\\rm H$i spectral stacking techniques with ASKAP.
Publisher: UNSWorks, UNSW
Date: 2020
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: UNSWorks, UNSW
Date: 2022
DOI: 10.26190/DY2G-Q958
Publisher: Cambridge University Press (CUP)
Date: 2023
DOI: 10.1017/PASA.2023.27
Abstract: The putative host galaxy of FRB 20171020A was first identified as ESO 601-G036 in 2018, but as no repeat bursts have been detected, direct confirmation of the host remains elusive. In light of recent developments in the field, we re-examine this host and determine a new association confidence level of 98%. At 37 Mpc, this makes ESO 601-G036 the third closest FRB host galaxy to be identified to date and the closest to host an apparently non-repeating FRB (with an estimated repetition rate limit of $ $ $0.011$ bursts per day above $10^{39}$ erg). Due to its close distance, we are able to perform detailed multi-wavelength analysis on the ESO 601-G036 system. Follow-up observations confirm ESO 601-G036 to be a typical star-forming galaxy with H i and stellar masses of $\\log_{10}\\!(M_{\\rm{H\\,{\\small I}}} / M_\\odot) \\sim 9.2$ and $\\log_{10}\\!(M_\\star / M_\\odot) = 8.64^{+0.03}_{-0.15}$ , and a star formation rate of $\\text{SFR} = 0.09 \\pm 0.01\\,{\\rm M}_\\odot\\,\\text{yr}^{-1}$ . We detect, for the first time, a diffuse gaseous tail ( $\\log_{10}\\!(M_{\\rm{H\\,{\\small I}}} / M_\\odot) \\sim 8.3$ ) extending to the south-west that suggests recent interactions, likely with the confirmed nearby companion ESO 601-G037. ESO 601-G037 is a stellar shred located to the south of ESO 601-G036 that has an arc-like morphology, is about an order of magnitude less massive, and has a lower gas metallicity that is indicative of a younger stellar population. The properties of the ESO 601-G036 system indicate an ongoing minor merger event, which is affecting the overall gaseous component of the system and the stars within ESO 601-G037. Such activity is consistent with current FRB progenitor models involving magnetars and the signs of recent interactions in other nearby FRB host galaxies.
Publisher: Springer Science and Business Media LLC
Date: 17-06-2022
DOI: 10.1007/S13178-022-00736-5
Abstract: Preexposure prophylaxis (PrEP) dosing options such as event-driven PrEP hold promise to increase PrEP uptake among gay, bisexual, and queer men (GBQM), but their impacts have not yet been realized and uptake by GBQM suitable for PrEP remains slow in countries where it is only considered an alternative option to daily PrEP. We conducted semi-structured interviews between June 2020 and February 2021 with 40 GBQM in Australia to understand PrEP dosing behaviors, knowledge, and preferences. All participants commenced PrEP daily 35% had ever switched to non-daily PrEP, mostly taking it event-driven. GBQM who preferred non-daily PrEP had infrequent or predictable sex, were concerned about cost given infrequency of sex, and/or wanted to minimize unnecessary drug exposure. Accurate knowledge of event-driven PrEP was poor. However, reflecting concepts underpinning critical pedagogy, having accurate knowledge was supported by access to consistent messaging across clinical, social, community, and public settings. Several participants who switched to event-driven PrEP had condomless sex events in which they were unable to adhere to pills due to unanticipated sex. Implementation of comprehensive and consistent education about correct dosing for event-driven PrEP across multiple settings is needed to ensure increased uptake and safe use. GBQM require messaging about non-condom based HIV prevention strategies when they cannot access daily or event-driven PrEP.
Publisher: Oxford University Press (OUP)
Date: 05-07-2021
Abstract: We present sofia 2, the fully automated 3D source finding pipeline for the WALLABY extragalactic H i survey with the Australian SKA Pathfinder (ASKAP). sofia 2 is a reimplementation of parts of the original sofia pipeline in the c programming language and makes use of OpenMP for multithreading of the most time-critical algorithms. In addition, we have developed a parallel framework called sofia-X that allows the processing of large data cubes to be split across multiple computing nodes. As a result of these efforts, sofia 2 is substantially faster and comes with a much reduced memory footprint compared to its predecessor, thus allowing the large WALLABY data volumes of hundreds of gigabytes of imaging data per epoch to be processed in real time. The source code has been made publicly available to the entire community under an open-source licence. Performance tests using mock galaxies injected into genuine ASKAP data suggest that in the absence of significant imaging artefacts sofia 2 is capable of achieving near-100 per cent completeness and reliability above an integrated signal-to-noise ratio (SNR) of about 5–6. We also demonstrate that sofia 2 generally recovers the location, integrated flux, and w20 line width of galaxies with high accuracy. Other parameters, including the peak flux density and w50 line width, are more strongly biased due to the influence of the noise on the measurement. In addition, very faint galaxies below an integrated SNR of about 10 may get broken up into multiple components, thus requiring a strategy to identify fragmented sources and ensure that they do not affect the integrity of any scientific analysis based on the sofia 2 output.
Publisher: Oxford University Press (OUP)
Date: 28-02-2023
Abstract: Galaxy morphology in atomic hydrogen (H i) and in the ultraviolet (UV) are closely linked. This has motivated their combined use to quantify morphology over the full H i disc for both H i and UV imaging. We apply galaxy morphometrics: concentration, asymmetry, gini, M20 and multimode-intensity-deviation statistics to the first moment-0 maps of the WALLABY Survey of galaxies in the hydra cluster centre. Taking advantage of this new H i survey, we apply the same morphometrics over the full H i extent on archival GALEX FUV and NUV data to explore how well H i truncated, extended ultraviolet disc (XUV) and other morphological phenomena can be captured using pipeline WALLABY data products. Extended H i and UV discs can be identified relatively straightforward from their respective concentration. Combined with WALLABY H i, even the shallowest GALEX data are sufficient to identify XUV discs. Our second goal is to isolate galaxies undergoing ram-pressure stripping in the H i morphometric space. We employ four different machine learning techniques, a decision tree, a k-nearest neighbour, a support-vector machine, and a random forest. Up to 80 per cent precision and recall are possible with the random forest giving the most robust results.
Publisher: UNSWorks, UNSW
Date: 2022
DOI: 10.26190/F57Q-0E06
Publisher: Springer Science and Business Media LLC
Date: 29-10-2018
Publisher: UNSW Centre for Social Research in Health, Sydney
Date: 2020
Publisher: Oxford University Press (OUP)
Date: 02-06-2021
Abstract: We report the discovery of large amounts of previously undetected cold neutral atomic hydrogen (H i) around the core triplet galaxies in the nearby NGC 7232 galaxy group with MeerKAT. With a physical resolution of ∼1 kpc, we detect a complex web of low-surface-brightness H i emission down to a 4σ column density level of ∼1 × 1019 cm−2 (over 44 km s−1). The newly discovered H i streams extend over ∼20 arcmin corresponding to 140 kpc in projection. This is approximately three times the H i extent of the galaxy triplet (52 kpc). The H i debris has an H i mass of ∼6.6 × 109 M⊙, more than 50 per cent of the total H i mass of the triplet. Within the galaxy triplet, NGC 7233 and NGC 7232 have lost a significant amount of H i while NGC 7232B appears to have an excess of H i. The H i deficiency in NGC 7232 and NGC 7233 indicates that galaxy–galaxy interaction in the group concentrates on this galaxy pair while the other disc galaxies have visited them over time. In comparison to the AMIGA s le of isolated galaxies, we find that with regards to its total H i mass the NGC 7232/3 galaxy triplet is not H i-deficient. Despite the many interactions associated to the triplet galaxies, no H i seems to have been lost from the group (yet).
Publisher: UNSWorks, UNSW
Date: 2020
Publisher: Cambridge University Press (CUP)
Date: 2020
DOI: 10.1017/PASA.2020.41
Abstract: The Rapid ASKAP Continuum Survey (RACS) is the first large-area survey to be conducted with the full 36-antenna Australian Square Kilometre Array Pathfinder (ASKAP) telescope. RACS will provide a shallow model of the ASKAP sky that will aid the calibration of future deep ASKAP surveys. RACS will cover the whole sky visible from the ASKAP site in Western Australia and will cover the full ASKAP band of 700–1800 MHz. The RACS images are generally deeper than the existing NRAO VLA Sky Survey and Sydney University Molonglo Sky Survey radio surveys and have better spatial resolution. All RACS survey products will be public, including radio images (with $\\sim$ 15 arcsec resolution) and catalogues of about three million source components with spectral index and polarisation information. In this paper, we present a description of the RACS survey and the first data release of 903 images covering the sky south of declination $+41^\\circ$ made over a 288-MHz band centred at 887.5 MHz.
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: UNSW Centre for Social Research in Health, Sydney
Date: 2021
DOI: 10.26190/JVDK-BG23
Publisher: UNSWorks, UNSW
Date: 2020
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 09-2021
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: Ovid Technologies (Wolters Kluwer Health)
Date: 06-2022
Publisher: UNSWorks, UNSW
Date: 2022
DOI: 10.26190/S8DV-S822
Publisher: American Astronomical Society
Date: 07-02-2018
Publisher: Cambridge University Press (CUP)
Date: 2021
DOI: 10.1017/PASA.2021.44
Abstract: The Variables and Slow Transients Survey (VAST) on the Australian Square Kilometre Array Pathfinder (ASKAP) is designed to detect highly variable and transient radio sources on timescales from 5 s to $\\sim\\!5$ yr. In this paper, we present the survey description, observation strategy and initial results from the VAST Phase I Pilot Survey. This pilot survey consists of $\\sim\\!162$ h of observations conducted at a central frequency of 888 MHz between 2019 August and 2020 August, with a typical rms sensitivity of $0.24\\ \\mathrm{mJy\\ beam}^{-1}$ and angular resolution of $12-20$ arcseconds. There are 113 fields, each of which was observed for 12 min integration time, with between 5 and 13 repeats, with cadences between 1 day and 8 months. The total area of the pilot survey footprint is 5 131 square degrees, covering six distinct regions of the sky. An initial search of two of these regions, totalling 1 646 square degrees, revealed 28 highly variable and/or transient sources. Seven of these are known pulsars, including the millisecond pulsar J2039–5617. Another seven are stars, four of which have no previously reported radio detection (SCR J0533–4257, LEHPM 2-783, UCAC3 89–412162 and 2MASS J22414436–6119311). Of the remaining 14 sources, two are active galactic nuclei, six are associated with galaxies and the other six have no multi-wavelength counterparts and are yet to be identified.
Publisher: Oxford University Press (OUP)
Date: 04-05-2018
Publisher: Oxford University Press (OUP)
Date: 31-10-2017
Publisher: UNSWorks, UNSW
Date: 2022
DOI: 10.26190/5PM2-RG76
Publisher: Oxford University Press (OUP)
Date: 31-07-2018
Publisher: Oxford University Press (OUP)
Date: 05-01-2019
DOI: 10.1093/MNRAS/STZ017
Abstract: We report on neutral hydrogen (H i) observations of the NGC 7232 group with the Australian Square Kilometre Array Pathfinder (ASKAP). These observations were conducted as part of the Wide-field ASKAP L-Band Legacy All-sky Blind surveY (WALLABY) Early Science program with an array of 12 ASKAP antennas equipped with Phased Array Feeds, which were used to form 36 beams to map a field of view of 30 deg2. Analysing a subregion of the central beams, we detect 17 H i sources. Eleven of these detections are identified as galaxies and have stellar counterparts, of which five are newly resolved H i galaxy sources. The other six detections appear to be tidal debris in the form of H i clouds that are associated with the central triplet, NGC 7232/3, comprising the spiral galaxies NGC 7232, NGC 7232B, and NGC 7233. One of these H i clouds has a mass of MH i ∼ 3 × 108 M⊙ and could be the progenitor of a long-lived tidal dwarf galaxy. The remaining H i clouds are likely transient tidal knots that are possibly part of a diffuse tidal bridge between NGC 7232/3 and another group member, the lenticular galaxy IC 5181.
Publisher: Oxford University Press (OUP)
Date: 09-2023
Publisher: Oxford University Press (OUP)
Date: 16-05-2016
Location: Brazil
No related grants have been discovered for Karen Lee-Waddell.