ORCID Profile
0000-0003-1657-7878
Current Organisation
Australian National University
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Astronomical and Space Sciences | Galactic Astronomy | Cosmology and Extragalactic Astronomy
Expanding Knowledge in the Physical Sciences | Scientific Instruments | Electronic Information Storage and Retrieval Services |
Publisher: American Astronomical Society
Date: 26-11-2021
Abstract: We present a follow-up analysis examining the dynamics and structures of 41 massive, large star-forming galaxies at z ∼ 0.67 − 2.45 using both ionized and molecular gas kinematics. We fit the galaxy dynamics with models consisting of a bulge, a thick, turbulent disk, and an NFW dark matter halo, using code that fully forward-models the kinematics, including all observational and instrumental effects. We explore the parameter space using Markov Chain Monte Carlo (MCMC) s ling, including priors based on stellar and gas masses and disk sizes. We fit the full s le using extracted 1D kinematic profiles. For a subset of 14 well-resolved galaxies, we also fit the 2D kinematics. The MCMC approach robustly confirms the results from least-squares fitting presented in Paper I: the s le galaxies tend to be baryon-rich on galactic scales (within one effective radius). The 1D and 2D MCMC results are also in good agreement for the subset, demonstrating that much of the galaxy dynamical information is captured along the major axis. The 2D kinematics are more affected by the presence of noncircular motions, which we illustrate by constructing a toy model with constant inflow for one galaxy that exhibits residual signatures consistent with radial motions. This analysis, together with results from Paper I and other studies, strengthens the finding that massive, star-forming galaxies at z ∼ 1 − 2 are baryon-dominated on galactic scales, with lower dark matter fractions toward higher baryonic surface densities. Finally, we present details of the kinematic fitting code used in this analysis.
Publisher: Oxford University Press (OUP)
Date: 05-10-2011
Publisher: American Astronomical Society
Date: 12-05-2017
Publisher: Oxford University Press (OUP)
Date: 21-01-2010
Publisher: Oxford University Press (OUP)
Date: 08-08-2017
Publisher: Oxford University Press (OUP)
Date: 29-01-2021
Abstract: We present a new model for the evolution of gas phase metallicity gradients in galaxies from first principles. We show that metallicity gradients depend on four ratios that collectively describe the metal equilibration time-scale, production, transport, consumption, and loss. Our model finds that most galaxy metallicity gradients are in equilibrium at all redshifts. When normalized by metal diffusion, metallicity gradients are governed by the competition between radial advection, metal production, and accretion of metal-poor gas from the cosmic web. The model naturally explains the varying gradients measured in local spirals, local dwarfs, and high-redshift star-forming galaxies. We use the model to study the cosmic evolution of gradients across redshift, showing that the gradient in Milky Way-like galaxies has steepened over time, in good agreement with both observations and simulations. We also predict the evolution of metallicity gradients with redshift in galaxy s les constructed using both matched stellar masses and matched abundances. Our model shows that massive galaxies transition from the advection-dominated to the accretion-dominated regime from high to low redshifts, which mirrors the transition from gravity-driven to star formation feedback-driven turbulence. Lastly, we show that gradients in local ultraluminous infrared galaxies (major mergers) and inverted gradients seen both in the local and high-redshift galaxies may not be in equilibrium. In subsequent papers in this series, we show that the model also explains the observed relationship between galaxy mass and metallicity gradients, and between metallicity gradients and galaxy kinematics.
Publisher: Oxford University Press (OUP)
Date: 2020
Abstract: We study the effect of the gas accretion rate ($\\dot{M}_{\\rm accr}$) on the radial gas metallicity profile (RMP) of galaxies using the eagle cosmological hydrodynamic simulations, focusing on central galaxies of stellar mass M⋆ ≳ 109 M⊙ at z ≤ 1. We find clear relations between $\\dot{M}_{\\rm accr}$ and the slope of the RMP (measured within an effective radius), where higher $\\dot{M}_{\\rm accr}$ are associated with more negative slopes. The slope of the RMPs depends more strongly on $\\dot{M}_{\\rm accr}$ than on stellar mass, star formation rate (SFR), or gas fraction, suggesting $\\dot{M}_{\\rm accr}$ to be a more fundamental driver of the RMP slope of galaxies. We find that eliminating the dependence on stellar mass is essential for pinning down the properties that shape the slope of the RMP. Although $\\dot{M}_{\\rm accr}$ is the main property modulating the slope of the RMP, we find that it causes other correlations that are more easily testable observationally: At fixed stellar mass, galaxies with more negative RMP slopes tend to have higher gas fractions and SFRs, while galaxies with lower gas fractions and SFRs tend to have flatter metallicity profiles within an effective radius.
Publisher: American Astronomical Society
Date: 26-06-2014
Publisher: Oxford University Press (OUP)
Date: 11-01-2023
Abstract: Previous studies have shown that the normalization and scatter of the galaxy ‘main sequence’ (MS), the relation between star formation rate (SFR) and stellar mass (M*), evolves over cosmic time. However, such studies often rely on photometric redshifts and/or only rest-frame UV to near-IR data, which may underestimate the SFR and M* uncertainties. We use MAGPHYS + photo-z to fit the UV to radio spectral energy distributions of 12 380 galaxies in the COSMOS field at 0.5 & z & 3.0, and self-consistently include photometric redshift uncertainties on the derived SFR and M*. We quantify the effect on the observed MS scatter from (1) photometric redshift uncertainties (which are minor) and (2) fitting only rest-frame ultraviolet to near-infrared observations (which are severe). At fixed redshift and M*, we find that the intrinsic MS scatter for our s le of galaxies is 1.4 to 2.6 times larger than the measurement uncertainty. The average intrinsic MS scatter has decreased by 0.1 dex from z = 0.5 to ∼2.0. At low z, the trend between the intrinsic MS scatter and M* follows a functional form similar to an inverse stellar mass-halo mass relation (SMHM M*/Mhalo versus M*), with a minimum in intrinsic MS scatter at log (M*/M⊙) ∼ 10.25 and larger scatter at both lower and higher M*, while this distribution becomes flatter for high z. The SMHM is thought to be a consequence of feedback effects and this similarity may suggest a link between galaxy feedback and the intrinsic MS scatter. These results favour a slight evolution in the intrinsic MS scatter with both redshift and mass.
Publisher: American Astronomical Society
Date: 02-2023
Abstract: We analyze H α or CO rotation curves extending out to several galaxy effective radii for 100 massive, large, star-forming disk galaxies (SFGs) across the peak of cosmic galaxy star formation ( z ∼ 0.6–2.5), more than doubling the previous s le presented by Genzel et al. and Price et al. The observations were taken with SINFONI and KMOS integral-field spectrographs at the ESO-Very Large Telescope, LUCI-LBT, NOEMA-IRAM, and Atacama Large Millimeter/submillimeter Array. We fit the major-axis kinematics with beam-convolved, forward models of turbulent rotating disks with bulges embedded in dark matter (DM) halos, including the effects of pressure support. The fraction of dark to total matter within the disk effective radius ( R e ∼ 5 kpc), f DM ( R e ) = V 2 DM ( R e )/ V 2 circ ( R e ) decreases with redshift: at z ∼ 1 ( z ∼ 2) the median DM fraction is 0.38 ± 0.23 (0.27 ± 0.18), and a third (half) of all galaxies are maximal disks with f DM ( R e ) 0.28. DM fractions correlate inversely with the baryonic surface density, and the low DM fractions can be explained with a flattened, or cored, inner DM density distribution. At z ∼ 2, there is ≈40% less DM mass on average within R e compared to expected values based on cosmological stellar-mass–halo-mass relations. The DM deficit is more evident at high star formation rate surface densities (≳2.5 M ⊙ yr −1 kpc 2 ) and galaxies with massive bulges (≥10 10 M ⊙ ). A combination of stellar or active galactic nucleus feedback, and/or heating due to dynamical friction, may drive the DM from cuspy into cored mass distributions, pointing to an efficient buildup of massive bulges and central black holes at z ∼ 2 SFGs.
Publisher: Springer Science and Business Media LLC
Date: 03-2017
DOI: 10.1038/NATURE21685
Abstract: In the cold dark matter cosmology, the baryonic components of galaxies-stars and gas-are thought to be mixed with and embedded in non-baryonic and non-relativistic dark matter, which dominates the total mass of the galaxy and its dark-matter halo. In the local (low-redshift) Universe, the mass of dark matter within a galactic disk increases with disk radius, becoming appreciable and then dominant in the outer, baryonic regions of the disks of star-forming galaxies. This results in rotation velocities of the visible matter within the disk that are constant or increasing with disk radius-a hallmark of the dark-matter model. Comparisons between the dynamical mass, inferred from these velocities in rotational equilibrium, and the sum of the stellar and cold-gas mass at the peak epoch of galaxy formation ten billion years ago, inferred from ancillary data, suggest high baryon fractions in the inner, star-forming regions of the disks. Although this implied baryon fraction may be larger than in the local Universe, the systematic uncertainties (owing to the chosen stellar initial-mass function and the calibration of gas masses) render such comparisons inconclusive in terms of the mass of dark matter. Here we report rotation curves (showing rotation velocity as a function of disk radius) for the outer disks of six massive star-forming galaxies, and find that the rotation velocities are not constant, but decrease with radius. We propose that this trend arises because of a combination of two main factors: first, a large fraction of the massive high-redshift galaxy population was strongly baryon-dominated, with dark matter playing a smaller part than in the local Universe and second, the large velocity dispersion in high-redshift disks introduces a substantial pressure term that leads to a decrease in rotation velocity with increasing radius. The effect of both factors appears to increase with redshift. Qualitatively, the observations suggest that baryons in the early (high-redshift) Universe efficiently condensed at the centres of dark-matter haloes when gas fractions were high and dark matter was less concentrated.
Publisher: Oxford University Press (OUP)
Date: 07-06-2011
Publisher: American Astronomical Society
Date: 28-11-2019
Publisher: American Astronomical Society
Date: 24-01-2017
Publisher: Oxford University Press (OUP)
Date: 05-05-2021
Abstract: In this paper, we analyse the statistics of the 2D gas-phase oxygen abundance distributions of 100 nearby galaxies drawn from the Calar Alto Legacy Integral Field spectroscopy Area survey. After removing the large-scale radial metallicity gradient, we compute the two-point correlation functions of the resulting metallicity fluctuation maps. We detect correlations in the majority of our targets, which we show are significantly in excess of what is expected due to beam-smearing, and are robust against the choice of metallicity diagnostic. We show that the correlation functions are generally well-fit by the predictions of a simple model for stochastic metal injection coupled with diffusion, and from the model we show that, after accounting for the effects of both beam smearing and noise, the galaxies in our s le have characteristic correlation lengths of ∼1 kpc. Correlation lengths increase with both stellar mass and star formation rate, but show no significant variation with Hubble type, barredness, or merging state. We also find no evidence for a theoretically predicted relationship between gas velocity dispersion and correlation length, though this may be due to the small dynamic range in gas velocity dispersion across our s le. Our results suggest that measurements of 2D metallicity correlation functions can be a powerful tool for studying galaxy evolution.
Publisher: American Astronomical Society
Date: 27-03-2014
Publisher: American Astronomical Society
Date: 23-09-2020
Publisher: Oxford University Press (OUP)
Date: 23-06-2011
Publisher: Oxford University Press (OUP)
Date: 05-2010
Publisher: Oxford University Press (OUP)
Date: 24-05-2013
DOI: 10.1093/MNRAS/STT520
Publisher: Oxford University Press (OUP)
Date: 19-07-2012
Publisher: Oxford University Press (OUP)
Date: 04-01-2013
DOI: 10.1093/MNRAS/STS431
Publisher: Oxford University Press (OUP)
Date: 20-04-2016
DOI: 10.1093/MNRAS/STW910
Publisher: Oxford University Press (OUP)
Date: 20-03-2013
DOI: 10.1093/MNRAS/STT320
Publisher: Oxford University Press (OUP)
Date: 02-05-2023
Abstract: We investigate the impact of environment on the internal mass distribution of galaxies using the Middle Ages Galaxy Properties with Integral field spectroscopy (MAGPI) survey. We use 2D resolved stellar kinematics to construct Jeans dynamical models for galaxies at mean redshift z ∼ 0.3, corresponding to a lookback time of 3–4 Gyr. The internal mass distribution for each galaxy is parametrized by the combined mass density slope γ (baryons + dark matter), which is the logarithmic change of density with radius. We use a MAGPI s le of 28 galaxies from low-to-mid density environments and compare to density slopes derived from galaxies in the high density Frontier Fields clusters in the redshift range 0.29 & z & 0.55, corresponding to a lookback time of ∼5 Gyr. We find a median density slope of γ = −2.22 ± 0.05 for the MAGPI s le, which is significantly steeper than the Frontier Fields median slope (γ = −2.00 ± 0.04), implying the cluster galaxies are less centrally concentrated in their mass distribution than MAGPI galaxies. We also compare to the distribution of density slopes from galaxies in ATLAS3D at z ∼ 0, because the s le probes a similar environmental range as MAGPI. The ATLAS3D median total slope is γ = −2.25 ± 0.02, consistent with the MAGPI median. Our results indicate environment plays a role in the internal mass distribution of galaxies, with no evolution of the slope in the last 3–4 Gyr. These results are in agreement with the predictions of cosmological simulations.
Publisher: American Astronomical Society
Date: 14-12-2015
Publisher: Oxford University Press (OUP)
Date: 31-05-2014
DOI: 10.1093/MNRAS/STU778
Publisher: American Astronomical Society
Date: 12-03-2018
Publisher: Oxford University Press (OUP)
Date: 15-12-2015
Publisher: American Astronomical Society
Date: 08-2016
Publisher: American Physical Society (APS)
Date: 16-11-2012
Publisher: Oxford University Press (OUP)
Date: 19-09-2011
Publisher: American Chemical Society (ACS)
Date: 21-01-2009
DOI: 10.1021/JA8088718
Abstract: Adsorption-desorption induced structural changes of Cu(bpy)(H(2)O)(2)(BF(4)),(bpy) (bpy = 4,4'-bipyridine) [Cu-MOF] have been evidenced by combined NMR and EPR spectroscopy. Upon adsorption of probe molecules even at a few mbar, EPR spectra show that they are activated to form complexes at Cu(II) sites, which results in a change of the Cu-MOF's structure as indicated by a high-field shift of the (11)B MAS NMR. After desorption, both EPR and (11)B MAS NMR spectra evidenced that the structure of the Cu-MOF reversibly shifted to the original state. This observation indicates that MOFs can undergo structural changes during processes where adsorption-desorption steps are involved such as gas storage, separation, and catalysis.
Publisher: Oxford University Press (OUP)
Date: 30-06-2014
Publisher: American Astronomical Society
Date: 30-01-2015
Publisher: Oxford University Press (OUP)
Date: 19-04-2022
Abstract: We present the first characterization of the average dust attenuation curve at z ∼ 1.3 by combining rest-frame ultraviolet through near-IR photometry with Balmer decrement (H α/H β) constraints for ∼900 galaxies with 8 ≲ log (M⋆/M⊙) & 10.2 at 0.75 & z & 1.5 in the HST WFC3 IR Spectroscopic Parallel and 3D-HST grism surveys. Using galaxies in SDSS, we establish that the (H α + [N ii])/[O iii] line ratio and stellar mass are good proxies for the Balmer decrement in low-spectral resolution grism data when only upper limits on H β are available and/or H α is blended with [N ii]. The slope of the z ∼ 1.3 attenuation curve ($A(0.15\\, \\rm{\\mu m})/A(V)=3.15$) and its normalization (RV = 3.26) lie in-between the values found for z = 0 and z ∼ 2 dust attenuation curves derived with similar methods. These provide supporting evidence that the average dust attenuation curve of star-forming galaxies evolves continuously with redshift. The z ∼ 1.3 curve has a mild 2175 Å feature (bump litude, Eb = 0.83 ∼25 per cent that of the MW extinction curve), which is comparable to several other studies at 0 & z ≲ 3, and suggests that the average strength of this feature may not evolve significantly with redshift. The methods we develop to constrain dust attenuation from HST grism data can be applied to future grism surveys with JWST, Euclid, and RST. These new facilities will detect millions of emission line galaxies and offer the opportunity to significantly improve our understanding of how and why dust attenuation curves evolve.
Publisher: American Physical Society (APS)
Date: 23-04-2012
Publisher: American Astronomical Society
Date: 06-04-2017
Publisher: American Astronomical Society
Date: 09-08-2016
Publisher: American Astronomical Society
Date: 15-10-2020
Publisher: Oxford University Press (OUP)
Date: 15-02-2023
Abstract: We explore local and global dynamical differences between the kinematics of ionized gas and stars in a s le of galaxies from Data Release 3 of the SAMI Galaxy Survey. We find better agreement between local (i.e. comparing on a spaxel-to-spaxel basis) velocities and dispersion of gas and stars in younger systems as with previous work on the asymmetric drift in galaxies, suggesting that the dynamics of stars and ionized gas are initially coupled. The intrinsic scatter around the velocity and dispersion relations increases with increasing stellar age and mass, suggesting that subsequent mechanisms, such as internal processes, ergent star formation, and assembly histories, also play a role in setting and altering the dynamics of galaxies. The global (flux-weighted) dynamical support of older galaxies is hotter than in younger systems. We find that the ionized gas in galaxies is almost always dynamically colder than the stars with a steeper velocity gradient. In absolute terms, the local difference in velocity dispersion is more pronounced than the local difference in velocity, possibly reflecting inherent differences in the impact of turbulence, inflow and/or feedback on gas compared to stars. We suggest how these findings may be taken into account when comparing high and low redshift galaxy s les to infer dynamical evolution.
Publisher: Elsevier BV
Date: 19-08-2010
Publisher: American Astronomical Society
Date: 03-2021
Abstract: We investigate what drives the redshift evolution of the typical electron density ( n e ) in star-forming galaxies, using a s le of 140 galaxies drawn primarily from KMOS 3D (0.6 z 2.6) and 471 galaxies from SAMI ( z 0.113). We select galaxies that do not show evidence of active galactic nucleus activity or outflows to constrain the average conditions within H ii regions. Measurements of the [S ii ] λ 6716/[S ii ] λ 6731 ratio in four redshift bins indicate that the local n e in the line-emitting material decreases from 187 cm −3 at z ∼ 2.2 to 32 cm −3 at z ∼ 0, consistent with previous results. We use the H α luminosity to estimate the rms n e averaged over the volumes of star-forming disks at each redshift. The local and volume-averaged n e evolve at similar rates, hinting that the volume filling factor of the line-emitting gas may be approximately constant across 0 ≲ z ≲ 2.6. The KMOS 3D and SAMI galaxies follow a roughly monotonic trend between n e and star formation rate, but the KMOS 3D galaxies have systematically higher n e than the SAMI galaxies at a fixed offset from the star-forming main sequence, suggesting a link between the n e evolution and the evolving main sequence normalization. We quantitatively test potential drivers of the density evolution and find that n e (rms) , suggesting that the elevated n e in high- z H ii regions could plausibly be the direct result of higher densities in the parent molecular clouds. There is also tentative evidence that n e could be influenced by the balance between stellar feedback, which drives the expansion of H ii regions, and the ambient pressure, which resists their expansion.
Publisher: American Astronomical Society
Date: 24-07-2019
Publisher: Wiley
Date: 02-08-2010
DOI: 10.1002/JBM.A.32801
Abstract: We developed a novel technique involving knitting and electrospinning to fabricate a composite scaffold for ligament tissue engineering. Knitted structures were coated with poly(L-lactic-co-e-caprolactone) (PLCL) and then placed onto a rotating cylinder and a PLCL solution was electrospun onto the structure. Highly aligned 2-microm-diameter microfibers covered the space between the stitches and adhered to the knitted scaffolds. The stress-strain tensile curves exhibited an initial toe region similar to the tensile behavior of ligaments. Composite scaffolds had an elastic modulus (150 +/- 14 MPa) similar to the modulus of human ligaments. Biological evaluation showed that cells proliferated on the composite scaffolds and they spontaneously orientated along the direction of microfiber alignment. The microfiber architecture also induced a high level of extracellular matrix secretion, which was characterized by immunostaining. We found that cells produced collagen type I and type III, two main components found in ligaments. After 14 days of culture, collagen type III started to form a fibrous network. We fabricated a composite scaffold having the mechanical properties of the knitted structure and the morphological properties of the aligned microfibers. It is difficult to seed a highly macroporous structure with cells, however the technique we developed enabled an easy cell seeding due to presence of the microfiber layer. Therefore, these scaffolds presented attractive properties for a future use in bioreactors for ligament tissue engineering.
Publisher: Oxford University Press (OUP)
Date: 07-02-2013
DOI: 10.1093/MNRAS/STS608
Publisher: American Astronomical Society
Date: 17-02-2012
Publisher: American Astronomical Society
Date: 09-01-2017
Publisher: Royal Society of Chemistry (RSC)
Date: 2009
DOI: 10.1039/B900791A
Abstract: Studying the rate of cell migration provides insight into fundamental cell biology as well as a tool to assess the functionality of synthetic surfaces and soluble environments used in tissue engineering. The traditional tools used to study cell migration include the fence and wound healing assays. In this paper we describe the development of a microchannel based device for the study of cell migration on defined surfaces. We demonstrate that this device provides a superior tool, relative to the previously mentioned assays, for assessing the propagation rate of cell wave fronts. The significant advantage provided by this technology is the ability to maintain a virgin surface prior to the commencement of the cell migration assay. Here, the device is used to assess rates of mouse fibroblasts (NIH 3T3) and human osteosarcoma (SaOS2) cell migration on surfaces functionalized with various extracellular matrix proteins as a demonstration that confining cell migration within a microchannel produces consistent and robust data. The device design enables rapid and simplistic assessment of multiple repeats on a single chip, where surfaces have not been previously exposed to cells or cellular secretions.
Publisher: Oxford University Press (OUP)
Date: 17-04-2012
Publisher: MDPI AG
Date: 30-01-2017
Publisher: American Astronomical Society
Date: 05-2014
Publisher: American Astronomical Society
Date: 09-04-2019
Publisher: Oxford University Press (OUP)
Date: 04-10-2011
Publisher: American Astronomical Society
Date: 03-11-2016
Publisher: Oxford University Press (OUP)
Date: 18-09-2013
Publisher: American Astronomical Society
Date: 26-05-2017
Publisher: Wiley
Date: 22-07-2011
DOI: 10.1002/BIT.23260
Abstract: Microfluidic systems create significant opportunities to establish highly controlled microenvironmental conditions for screening pluripotent stem cell fate. However, since cell fate is crucially dependent on this microenvironment, it remains unclear as to whether continual perfusion of culture medium supports pluripotent stem cell maintenance in feeder-free, chemically defined conditions, and further, whether optimum perfusion conditions exist for subsequent use of human embryonic stem cell (hESCs) in other microfludic systems. To investigate this, we designed microbioreactors based on resistive flow to screen hESCs under a linear range of flowrates. We report that at low rates (conditions where glucose transport is convection-limited with Péclet number 95% of cells over 7 days. For MEL1 hESCs the optimum flowrate also coincided with the time-averaged medium exchange rate in static cultures, which may therefore provide a good first estimate of appropriate perfusion rates. Overall, we demonstrate hESCs can be maintained in microbioreactors under continual flow for up to 7 days, a critical outcome for the future development of microbioreactor-based screening systems and assays for hESC culture.
Publisher: American Astronomical Society
Date: 04-04-2019
Publisher: Oxford University Press (OUP)
Date: 05-12-2022
Abstract: This paper presents deep K-band spectroscopic observations of galaxies at z = 3 − 4 with composite photometric rest-frame H β+[O iii] 5007 equivalent widths (EW0) & 600 Å, comparable to the EW of galaxies observed during the epoch of reionization (EoR, z & 6). The typical spectroscopic [O iii] 5007 EW0 and stellar mass of our targets is ∼700 Å and log (M*/M⊙) = 8.98. By stacking the [O iii] 5007 emission profiles, we find evidence of a weak broad component with $\\rm F_{broad}/F_{narrow} \\sim 0.2$ and velocity width σbroad ∼ 170 km s−1. The strength and velocity width of the broad component does not change significantly with stellar mass and [O iii] 5007 EW0 of the stacked s le. Assuming similar broad component profiles for [O iii] 5007 and Hα emission, we estimate a mass loading factor ∼0.2, similar to low stellar mass galaxies at z & 1 even if the star formation rates of our s le is 10 times higher. We hypothesize that either the multiphase nature of supernovae driven outflows or the suppression of winds in the extreme star-forming regime is responsible for the weak signature of outflows in the EoR analogues.
Publisher: American Astronomical Society
Date: 22-06-2017
Publisher: Oxford University Press (OUP)
Date: 21-10-2022
Abstract: We analyse the spatial statistics of the 2D gas-phase oxygen abundance distributions in a s le of 219 local galaxies. We introduce a new adaptive binning technique to enhance the signal-to-noise ratio of weak lines, which we use to produce well-filled metallicity maps for these galaxies. We show that the two-point correlation functions computed from the metallicity distributions after removing radial gradients are in most cases well-described by a simple injection–diffusion model. Fitting the data to this model yields the correlation length lcorr, which describes the characteristic interstellar medium (ISM) mixing length-scale. We find typical correlation lengths lcorr ∼ 1 kpc, with a strong correlation between lcorr and stellar mass, star formation rate (SFR), and effective radius, and a weak correlation with Hubble type. Two galaxies in the s le show significantly larger lcorr, and both prove to be interacting or merging systems. We show that the trend of lcorr with SFR can be reproduced by a simple transport + feedback model of ISM turbulence at high SFR, and plausibly also at low SFR if dwarf galaxy winds have large mass-loading factors. We also report the first measurements of the injection width that describes the initial radii over which supernova remnants deposit metals. Inside this radius the metallicity correlation function is not purely the product of a competition between injection and diffusion. We show that this size scale is generally smaller than 60 pc.
Publisher: American Astronomical Society
Date: 17-05-2017
Publisher: Elsevier BV
Date: 11-2010
DOI: 10.1016/J.BIOMATERIALS.2010.07.007
Abstract: As strategies for manipulating cellular behaviour in vitro and in vivo become more sophisticated, synthetic biomaterial substrates capable of reproducing critical biochemical and biophysical properties (or cues) of tissue micro-environments will be required. Cytoskeletal tension has been shown to be highly deterministic of cell fate decisions, yet few synthetic biomaterials are capable of modulating cytoskeletal tension of adhered cells through variations in stiffness, at least in the ranges applicable to tissue properties (e.g., 1-100 kPa), whilst also possessing other required properties, such as biodegradability, biocompatibility and processability. In this paper we describe a non-cytotoxic polymer system based on acrylated polypropylene glycol triol (aPPGT). This new elastomer system has tunable elastic moduli, is degradable, can be easily surface modified and can be manufactured into porous three dimensional scaffolds or micropatterned substrates. We demonstrate that the PPGT substrates can modulate hMSC morphology, growth, and differentiation, and that they can produce similar outcomes as observed for a non-degradable polyacrylamide substrate, confirming their utility as a degradable elastomer for tissue engineering and other biomedical applications.
Publisher: Oxford University Press (OUP)
Date: 21-08-2023
Publisher: Oxford University Press (OUP)
Date: 13-11-2013
Publisher: American Astronomical Society
Date: 19-03-2020
Publisher: Oxford University Press (OUP)
Date: 26-03-2021
Abstract: In addition to the well-known gas phase mass–metallicity relation (MZR), recent spatially resolved observations have shown that local galaxies also obey a mass–metallicity gradient relation (MZGR), whereby metallicity gradients can vary systematically with galaxy mass. In this work, we use our recently developed analytic model for metallicity distributions in galactic discs, which includes a wide range of physical processes – radial advection, metal diffusion, cosmological accretion, and metal-enriched outflows – to simultaneously analyse the MZR and MZGR. We show that the same physical principles govern the shape of both: centrally peaked metal production favours steeper gradients, and this steepening is diluted by the addition of metal-poor gas, which is supplied by inward advection for low-mass galaxies and by cosmological accretion for massive galaxies. The MZR and the MZGR both bend at galaxy stellar mass $\\sim 10^{10}{-}10^{10.5}\\, \\rm {M_{\\odot }}$, and we show that this feature corresponds to the transition of galaxies from the advection-dominated to the accretion-dominated regime. We also find that both the MZR and MZGR strongly suggest that low-mass galaxies preferentially lose metals entrained in their galactic winds. While this metal-enrichment of the galactic outflows is crucial for reproducing both the MZR and the MZGR at the low-mass end, we show that the flattening of gradients in massive galaxies is expected regardless of the nature of their winds.
Publisher: Cambridge University Press (CUP)
Date: 07-2014
DOI: 10.1017/S1743921314009788
Abstract: The KMOS 3D survey will provide near-IR IFU observations of a mass-selected s le of ∼600 star-forming galaxies at 0.7 z .7 with the K-band Multi Object Spectrograph (KMOS) at the VLT. We present kinematic results for a first s le of ∼200 galaxies, focusing on the evolution of the gas velocity dispersion with redshift. Combined with existing measurements, we find an approximate (1+ z ) evolution from z ∼4 to the present day, which can be understood from the co-evolution of the gas fraction and specific star formation rate (sSFR) in the the equilibrium picture of galaxy evolution. We combine the KMOS 3 D s le with data from the LUCI and SINFONI spectrographs, as well as multi-wavelength HST imaging from CANDELS, to address the relations between stellar mass, SFR, and the [N II]/Hα flux ratio as an indicator of gas-phase metallicity for a s le of 222 star-forming galaxies. We find a constant slope at the low-mass end of the mass-metallicity relation and can fully describe its redshift evolution through the evolution of the characteristic turnover mass where the relation begins to flatten at the asymptotic metallicity. At a fixed mass and redshift, our data do not show a correlation between the [N II]/Hα ratio and SFR.
Publisher: Oxford University Press (OUP)
Date: 14-09-2017
Publisher: American Astronomical Society
Date: 16-02-2018
Publisher: Oxford University Press (OUP)
Date: 04-10-2011
Publisher: Oxford University Press (OUP)
Date: 26-07-2012
Publisher: Cambridge University Press (CUP)
Date: 03-2016
DOI: 10.1017/S1743921316011315
Abstract: We exploit the deep Hα IFU kinematic data from the KMOS 3D and SINS/zC-SINF surveys to explore the so far unconstrained outer rotation curves of star-forming disk galaxies at high redshift. Through stacking the signal of ~ 100 massive disks at 0.7 z 2.6, we construct a representative rotation curve reaching out to several effective radii. Our stacked rotation curve exhibits a turnover with a steep falloff in the outer regions, significantly strengthening the tantalizing evidence previously hinted at in a handful only of in idual disks among the s le with the deepest data. This finding confirms the high baryon fractions found by comparing the stellar, gas and dynamical masses of high redshift galaxies independently of assumptions on the light-to-mass conversion and Initial stellar Mass Function (IMF). The rapid falloff of the stacked rotation curve is most naturally explained by the effects of pressure gradients, which are significant in the gas-rich, turbulent high-z disks and which would imply a possible pressure-driven truncation of the outer disk.
Publisher: Oxford University Press (OUP)
Date: 06-06-2019
Publisher: Oxford University Press (OUP)
Date: 21-11-2018
Publisher: American Astronomical Society
Date: 29-10-2014
Publisher: American Astronomical Society
Date: 13-03-2019
Publisher: Oxford University Press (OUP)
Date: 21-08-2023
Publisher: American Astronomical Society
Date: 18-07-2014
Publisher: Oxford University Press (OUP)
Date: 09-07-2013
Publisher: Oxford University Press (OUP)
Date: 07-2021
Abstract: In this work, we explore the ersity of ionized gas kinematics (rotational velocity vϕ and velocity dispersion σg) and gas-phase metallicity gradients at 0.1 ≤ z ≤ 2.5 using a compiled data set of 74 galaxies resolved with ground-based integral field spectroscopy. We find that galaxies with the highest and the lowest σg have preferentially flat metallicity gradients, whereas those with intermediate values of σg show a large scatter in the metallicity gradients. Additionally, steep negative gradients appear almost only in rotation-dominated galaxies (vϕ/σg & 1), whereas most dispersion-dominated galaxies show flat gradients. We use our recently developed analytical model of metallicity gradients to provide a physical explanation for the shape and scatter of these observed trends. In the case of high σg, the inward radial advection of gas dominates over metal production and causes efficient metal mixing, thus giving rise to flat gradients. For low σg, it is the cosmic accretion of metal-poor gas diluting the metallicity that gives rise to flat gradients. Finally, the reason for intermediate σg showing the steepest negative gradients is that both inward radial advection and cosmic accretion are weak as compared to metal production, which leads to the creation of steeper gradients. The larger scatter at intermediate σg may be due in part to preferential ejection of metals in galactic winds, which can decrease the strength of the production term. Our analysis shows how gas kinematics play a critical role in setting metallicity gradients in high-redshift galaxies.
Publisher: American Astronomical Society
Date: 05-2020
Publisher: Oxford University Press (OUP)
Date: 17-07-2023
Abstract: We use the eagle cosmological simulations to study the evolution of the vertical velocity dispersion of cold gas, σz, in central disc galaxies and its connection to stellar feedback, gravitational instabilities, cosmological gas accretion, and galaxy mergers. To isolate the impact of feedback, we analyse runs that turn off stellar and (or) active galactic nuclei feedback in addition to a run that includes both. The evolution of σz and its dependence on stellar mass and star formation rate in eagle are in good agreement with observations. Galaxies hosted by haloes of similar virial mass, $\\rm M_{200}$, have similar σz values even in runs where feedback is absent. The prevalence of local instabilities in discs is uncorrelated with σz at low redshift and becomes only weakly correlated at high redshifts and in galaxies hosted by massive haloes. σz correlates most strongly with the specific gas accretion rate onto the disc as well as with the degree of misalignment between the inflowing gas and the disc’s rotation axis. These correlations are significant across all redshifts and halo masses, with misaligned accretion being the primary driver of high gas turbulence at redshifts z ≲ 1 and for halo masses $\\rm M_{200} \\lesssim 10^{11.5} {\\rm M}_{\\odot }$. Galaxy mergers increase σz, but because they are rare in our s le, they play only a minor role in its evolution. Our results suggest that the turbulence of cold gas in eagle discs results from a complex interplay of different physical processes whose relative importance depends on halo mass and redshift.
Publisher: Oxford University Press (OUP)
Date: 08-06-2023
Abstract: We report spatially resolved dust properties of the quasar host galaxy BRI1335−0417 at redshift z = 4.4 constrained by the Atacama Large Millimetre/submillimetre Array observations. The dust temperature map, derived from a greybody fit to rest frame 90 and 161 μm continuum images, shows a steep increase towards the centre, reaching 57.1 ± 0.3 K and a flat median profile at the outer regions of ∼38 K. Image decomposition analysis reveals the presence of a point source in both dust continuum images spatially coincident with the highest temperature peak and the optical quasar position, which we attribute to warm dust heated by an active galactic nucleus (AGN). We show that a model including this warm component along with cooler dust heated by star formation describes the global spectral energy distribution better than a single-component model, with dust temperatures of 87.1$^{+34.1}_{-18.3}$ K (warm component) and 52.6$^{+10.3}_{-11.0}$ K (cold component). The star-formation rate (SFR) estimated from the cold dust component is $1700_{-400}^{+500}\\ \\mathrm{M}_\\odot$ yr−1, a factor of three smaller than previous estimates due to a large AGN contribution ($53^{+14}_{-15}$ per cent). The unresolved warm dust component also explains the steep temperature gradient, as the temperature profile derived after the point source subtraction is flat. The point source subtraction also reduces the estimated central SFR surface density ΣSFR by over a factor of three. With this correction, spatially resolved measurements of ΣSFR and the surface gas mass density Σgas form a roughly linear sequence in the Kennicutt–Schmidt diagram with a constant gas depletion time of 50–200 Myr. The demonstrated AGN-host galaxy decomposition reveals the importance of spatially resolved data for accurate measurements of quasar host galaxy properties, including dust temperature, SFRs, and size.
Publisher: Elsevier BV
Date: 06-2011
DOI: 10.1016/J.ACTBIO.2011.02.036
Abstract: This study investigates the use of patterned collectors to increase the pore size of electrospun scaffolds for enhanced cell infiltration. The morphology of the patterned scaffolds was investigated by scanning electron microscopy, which showed that the collector pattern was accurately mimicked by the electrospun fibres. We observed an enlargement in the pore size and in the pore size distribution compared with conventional electrospinning. Mechanical testing revealed that the mechanical properties could be tailored, to some extent, according to the patterning and that the patterned scaffolds were softer than standard electrospun scaffolds. When NIH 3T3 fibroblasts were seeded onto patterned collectors improved cell infiltration was observed. Cells were able to penetrate up to 250 μm into the scaffolds, compared with 30 μm for the standard scaffolds. This increase in the depth of infiltration occurred as early as 24 h post-seeding and remained constant over 7 days.
Start Date: 07-2017
End Date: 12-2024
Amount: $30,300,000.00
Funder: Australian Research Council
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