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We update the treatment of chemical evolution in the Munich semi-analytic model, L-GALAXIES. Our new implementation includes delayed enrichment from stellar winds, supernovæ type II (SNe-II) and supernovæ type Ia (SNe-Ia), as well as metallicity-dependent yields and a reformulation of the associated supernova feedback. Two different sets of SN-II yields and three different SN-Ia delay-time distributions (DTDs) are considered, and eleven heavy elements (including O, Mg and Fe) are self-consistently tracked. We compare the results of this new implementation with data on a) local, star-forming galaxies, b) Milky Way disc G dwarfs, and c) local, elliptical galaxies. We find that the z = 0 gas-phase mass-metallicity relation is very well reproduced for all forms of DTD considered, as is the [Fe/H] distribution in the Milky Way disc. The [O/Fe] distribution in the Milky Way disc is best reproduced when using a DTD with less than or equal to 50 per cent of SNe-Ia exploding within ~ 400 Myrs. Positive slopes in the mass-[α/Fe] relations of local ellipticals are also obtained when using a DTD with such a minor ‘prompt’ component. Alternatively, metal-rich winds that drive light α elements directly out into the circumgalactic medium also produce positive slopes for all forms of DTD and SN-II yields considered. Overall, we find that the best model for matching the wide range of observational data considered here should include a power-law SN-Ia DTD, SN-II yields that take account of prior mass loss through stellar winds, and some direct ejection of light α elements out of galaxies.

2) Modelling Element Abundances in Semi-analytic Models of Galaxy Formation

Robert M. Yates, Bruno Henriques, Peter A. Thomas, Guinevere Kauffmann, Jonas Johansson & Simon D. M. White  |  2013, MNRAS, 435, 3500

2) Star Formation and Metallicity Gradients in Semi-analytic Models of Disk Galaxy Formation

Jian Fu, Guinevere Kauffmann, Mei-ling Huang, Robert M. Yates, Sean Moran, Timothy M. Heckman, Romeel Dave', Qi Guo  |  2013, MNRAS, 434, 1531

We have updated our radially-resolved semi-analytic models of galaxy formation to track the radial distribution of stars, metals, atomic and molecular gas in galactic disks. The models are run on dark matter halo merger trees from the Millennium and Millennium II simulations using the physical recipes outlined in Fu et al. (2010) and Guo et al. (2011), with 3 main changes: (1) We adopt a simple star formation law where the star formation rate surface density is proportional to the surface density of molecular gas (SFR / H2 ). (2) We inject a fraction of the heavy elements produced by supernovae directly into the halo, instead of first mixing them with the cold gas in the disk. (3) We include radial gas inflows in disks using a model of the form vinflow = αr. The average surface density profiles of molecular gas in L∗ galaxies place strong constraints on inflow velocities, favouring models where vinflow  7 km/s at a galactocentric radius of 10 kpc. The radial inflow model has little influence on the gas and stellar metallicity gradients in the outer regions of galaxies. Gas-phase metallicity gradients are affected much more strongly by the fraction of metals that are directly injected into the halo gas, rather than mixed with the interstellar cold gas of the galaxy. Metals ejected out of the galaxy at early epochs result in late infall of pre-enriched gas and flatter present-day gas-phase metallicity gradients. A prescription in which 80 % of all the metals produced by stars are injected into the halo gas provides the best fit to the relatively flat observed metallicity gradients of galaxies with stellar masses greater than 10^10M⊙. Such a prescription also results in a good fit to the relation between gas-phase metallicity and specific star formation rate in the outer parts of galactic disks. We examine the correlation between gas-phase metallicity gradient and a number of global galaxy properties, finding that it is most strongly correlated with the bulge-to-disk ratio of the galaxy. This is because gas is consumed when the bulge forms during the galaxy merger, and the gas-phase metallicity gradient is then set by newly-accreted gas. These model predictions appear to be in good agreement with observations from Moran et al. (2012).

Square Square

We study relations between stellar mass, star formation and gas-phase metallicity in a sample of 177,071 unique emission line galaxies from the SDSS-DR7, as well as in a sample of 43,767 star forming galaxies at z=0 from the cosmological semi-analytic model L-GALAXIES. We demonstrate that metallicity is dependent on star formation rate at fixed mass, but that the trend is opposite for low and for high mass galaxies. Low-mass galaxies that are actively forming stars are more metal-poor than quiescent low-mass galaxies. High-mass galaxies, on the other hand, have lower gas-phase metallicities if their star formation rates are small. Remarkably, the same trends are found for our sample of model galaxies. We find that massive model galaxies with low gas-phase metallicities have undergone a gas-rich merger in the past, inducing a starburst which exhausted their cold gas reservoirs and shut down star formation. This led to a gradual dilution in the gas-phase metallicities of these systems via accretion of gas. These model galaxies have lower-than-average gas-to-stellar mass ratios and higher-than-average central black hole masses. We confirm that massive galaxies with low gas-phase metallicities in our observational sample also have very massive black holes. We propose that accretion may therefore play a significant role in regulating the gas-phase metallicities of present-day massive galaxies.

1) The relation between metallicity, stellar mass and star formation in galaxies: an analysis of observational and model data

Robert M. Yates, Guinevere Kauffmann & Qi Guo  |  2012, MNRAS, 422, 215

First-author papers:

Co-authored papers:

1) The observed relation between stellar mass, dust extinction and star formation rate in local galaxies

H. J. Zahid, R. M. Yates, L. J. Kewley, R. P. Kudritzki  |  2013, ApJ, 763, 92

In this study we investigate the relation between stellar mass, dust extinction and star formation rate (SFR) using ~150,000 star-forming galaxies from the SDSS DR7. We show that the relation between dust extinction and SFR changes with stellar mass. For galaxies at the same stellar mass dust extinction is anti-correlated with the SFR at stellar masses <10^10 M_solar. There is a sharp transition in the relation at a stellar mass of 10^10 M_solar. At larger stellar masses dust extinction is positively correlated with the SFR for galaxies at the same stellar mass. The observed relation between stellar mass, dust extinction and SFR presented in this study helps to confirm similar trends observed in the relation between stellar mass, metallicity and SFR. The relation reported in this study provides important new constraints on the physical processes governing the chemical evolution of galaxies. The correlation between SFR and dust extinction for galaxies with stellar masses >10^10 M_solar is shown to extend to the population of quiescent galaxies suggesting that the physical processes responsible for the observed relation between stellar mass, dust extinction and SFR may be related to the processes leading to the shut down of star formation in galaxies.


3) Dilution in elliptical galaxies: Implications for the relation between metallicity, stellar mass and star formation rate

Robert M. Yates & Guinevere Kauffmann | 2014, MNRAS, 439, 3817


We investigate whether gradual dilution of the gas in some elliptical galaxies is the cause of a positive correlation between star formation rate (SFR) and gas-phase metallicity (Zg) at high stellar mass (M*) in the local Universe. To do this, two classes of massive (M* >= 10^10.5 Msun) galaxy are selected from the Sloan Digital Sky Survey (SDSS) and the Munich semi-analytic model of galaxy formation, L-Galaxies. The first class is selected by high specific star formation rates (sSFR) and high Zg, and the second class by low sSFR and low Zg. These criteria roughly distinguish disc-dominant galaxies from metal-poor, elliptical galaxies. In the semi-analytic model, the second class of galaxies obtain low sSFR and low Zg due to gradual dilution of the interstellar medium by accretion of metal-poor gas via infalling clumps and low-mass satellites. This occurs after a merger-induced starburst and the associated supernova feedback have quenched most of the original gas reservoir. A number of signatures of this evolution are present in these model galaxies at z=0, including low gas fractions, large central black holes, elliptical morphologies, old ages, and importantly, low (Zg-Z*) indicating dilution after star formation. Remarkably, all of these properties are also found in low-sSFR, low-Zg, massive galaxies in the SDSS-DR7. This provides strong, indirect evidence that some elliptical galaxies are undergoing gradual dilution after a gas-rich merger in the local Universe. This dilution scenario also explains the positive correlation between SFR and Zg measured in high-M* galaxies, and therefore has consequences for the local fundamental metallicity relation (FMR), which assumes a weak anti-correlation between SFR and Zg above ~10^10.5 Msun.

4) Iron in galaxy groups & clusters: Confronting galaxy evolution models with a newly homogenised dataset

Robert M. Yates, Peter Thomas & Bruno Henriques | 2017, MNRAS, 464, 3169

We present an analysis of the iron abundance in the hot gas surrounding galaxy groups and clusters. To do this, we first compile and homogenise a large dataset of 79 low-redshift (|z| = 0.03) systems (159 individual measurements) from the literature. Our analysis accounts for differences in aperture size, solar abundance, and cosmology, and scales all measurements using customised radial profiles for the temperature (T), gas density (ρ), and iron abundance (Z). We then compare this dataset to groups and clusters in the Munich semi-analytic model of galaxy evolution, L-Galaxies.


Our homogenised dataset reveals a tight T-Z relation for clusters, with a scatter in Z of only 0.10 dex and a slight negative gradient. After examining potential measurement biases, we conclude that at least some of this negative gradient has a physical origin. Our galaxy evolution model suggests greater accretion of hydrogen in the hottest systems, via stripping of gas from infalling satellites, as a cause. At lower temperatures, our model over-estimates Z in groups, indicating that metal-rich gas removal (via e.g. AGN feedback) is required.


L-Galaxies provides a reasonable match to the observed Z in the intracluster medium (ICM) of the hottest clusters from at least z  1.3 to 0.3. This is achieved without needing to modify any galactic chemical evolution (GCE) parameters. L-Galaxies is therefore able to reproduce this result simultaneously with the chemical properties of (a) the star-forming gas in local emission-line galaxies, (b) the MilkyWay stellar disc, and (c) the integrated stellar populations of nearby ellipticals. However, the Z in intermediate-T clusters appears to be under-estimated in our model at z = 0. The merits and problems with modifying the ICM enrichment modelling to correct this are discussed.


3) A sub-solar metallicity is required for superluminous supernova progenitors

T.-W. Chen, S. J. Smartt, R. M. Yates, M. Nicholl, T. Krühler, P. Schady, M. Dennefeld, C. Inserra, 2016, submitted to MNRAS

Host galaxy properties provide strong constraints on the stellar progenitors of superluminous supernovae. By comparing a sample of 18 low-redshift superluminous supernova hosts to a volume-limited galaxy population in the local Universe, we show that sub-solar metallici- ties seems to be a requirement. All superluminous supernovae in hosts with high measured gas-phase metallicities are found to explode at large galactocentric radii, indicating that the metallicity at the explosion site is likely lower than the integrated host value. We also confirm that high specific star-formation rates are a feature of superluminous supernova host galaxies, but interpret this as simply a consequence of the anti-correlation between gas-phase metallic- ity and specific star-formation rate and the requirement of on-going star formation to produce young, massive stars greater than ~ 10-20 M_sun . Based on our sample, we propose an upper limit of ~ 0.5 Z_sun for forming superluminous supernova progenitors (assuming an N2 metal- licity diagnostic and a solar oxygen abundance of 8.69). Finally, we show that if magnetar powering is the source of the extreme luminosity then the required initial spins appear to be correlated with metallicity of the host galaxy. This correlation needs further work, but if it holds it is a powerful link between the supernova parameters and nature of the progenitor population.


4) Self-similarity in the chemical evolution of galaxies and the delay time distribution of SNe Ia

C.J. Walcher, R.M. Yates, I. Minchev, C. Chiappini, M. Bergemann, G. Bruzual, S. Charlot, P.R.T. Coelho, A. Gallazzi & M. Martig, 2016, accepted by A&A

Recent improvements in the age dating of stellar populations and single stars allow us to study the ages and abundance of stars and galaxies with unprecedented accuracy. We here compare the relation between age and \alpha-element abundances for stars in the solar neighborhood to that of local, early-type galaxies. We find both relations to be very similar. Both fall into two regimes with a flat slope for ages younger than ~9 Gyr and a steeper slope for ages older than that value. This quantitative similarity seems surprising, given the different types of galaxies and scales involved. For the sample of early-type galaxies we also show that the data are inconsistent with literature delay time distributions of either single or double Gaussian shape. The data are consistent with a power law delay time distribution. We thus confirm that the delay time distribution inferred for the Milky Way from chemical evolution arguments also must apply to massive early-type galaxies. We also offer a tentative explanation for the seeming universality of the age-[\alpha/Fe] relation as the manifestation of averaging of different stellar populations with varying chemical evolution histories.


5) The evolution of the dust-to-metals ratio in high-redshift galaxies probed by GRB-DLAs

P. Wiseman, P. Schady, J. Bolmer, T. Krühler, R. M. Yates, J. Greiner & J. P. U. Fynbo, 2016, submitted to A&A

Several issues regarding the nature of dust at high redshift remain unresolved: its composition, its production and growth mechanisms, and its effect on background sources. Aims: This paper aims to provide a more accurate relation between dust depletion levels and dust-to-metals ratio (DTM), and to use the DTM to investigate the origin and evolution of dust in the high redshift Universe via GRB-DLAs.

We use absorption-line measured metal column densities for a total of 19 GRB-DLAs, including five new GRB afterglow spectra from VLT/X-shooter. We use the latest linear models to calculate the dust depletion strength factor in each DLA. Using this we calculate total dust and metal column densities to determine a DTM. We explore the evolution of DTM with metallicity, and compare this to previous trends in DTM measured with different methods.

We find significant dust depletion in 16 of our 19 GRB-DLAs, yet 18 of the 19 have a DTM significantly lower than the Milky Way. We find that DTM is positively correlated with metallicity, which supports a dominant ISM-grain-growth mode of dust formation. We find a substantial discrepancy between the dust content measured from depletion and that derived from the total V-band extinction, AV, measured by fitting the afterglow SED. We advise against using a measurement from one method to estimate that from the other, until the discrepancy can be resolved.


6) Evidence for the magnetar nature of 1E 161348-5055 in RCW 103

A. D'Ai et al. | 2016, MNRAS, 463, 2394

We report on the detection of a bright, short, structured X-ray burst coming from the supernova remnant RCW 103 on 2016 June 22 caught by the Swift/BAT monitor, and on the follow-up campaign made with Swift/XRT, Swift/UVOT and the optical/NIR GROND detector. The characteristics of this flash, such as duration and spectral shape, are consistent with typical short bursts observed from soft gamma repeaters. The BAT error circle at 68% confidence range encloses the point-like X-ray source at the centre of the nebula, 1E 161348-5055. Its nature has been long debated due to a periodicity of 6.67 hr in X-rays, which could indicate either an extremely slow pulsating neutron star, or the orbital period of a very compact X-ray binary system. We found that 20 minutes before the BAT trigger, the soft X-ray emission of 1E 161348-5055 was a factor of ˜ 100 higher than measured two years earlier, indicating that an outburst had already started. By comparing the spectral and timing characteristics of the source in the two years before the outburst and after the BAT event, we find that, besides a change in luminosity and spectral shape, also the 6.67 hr pulsed profile has significantly changed with a clear phase shift with respect to its low-flux profile. The UV/optical/NIR observations did not reveal any counterpart at the position of 1E 161348-5055. Based on these findings, we associate the BAT burst with 1E 161348-5055, we classify it as a magnetar, and pinpoint the 6.67 hr periodicity as the magnetar spin period.


Image credit: GROND Deep Field

6th December 2015

R. Yates (MPE) & D. A. Kann (TLS)

7) The evolution of superluminous supernova LSQ14mo and its interacting host galaxy system

Chen, Nicholl, Smartt, Mazzali, Yates, et al., 2017, A&A, 602, 9

We present and analyse an extensive dataset of the superluminous supernova LSQ14mo (z = 0.256), consisting of a multi-colour lightcurve from −30 d to +70 d in the rest-frame (relative to maximum light) and a series of 6 spectra from PESSTO covering −7 d to +50 d. This is among the densest spectroscopic coverage, and best-constrained rising lightcurve, for a fast-declining hydrogen-poor superluminous supernova. The bolometric lightcurve can be reproduced with a millisecond magnetar model with ∼ 4 M ejecta mass, and the temperature and velocity evolution is also suggestive of a magnetar as the power source. Spectral modelling indicates that the SN ejected ∼ 6 Msun of CO-rich material with a kinetic energy of ∼ 7 × 1051 erg, and suggests a partially thermalised additional source of luminosity between −2 d and +22 d. This may be due to interaction with a shell of material originating from pre-explosion mass loss. We further present a detailed analysis of the host galaxy system of LSQ14mo. PESSTO and GROND imaging show three spatially resolved bright regions, and we used the VLT and FORS2 to obtain a deep (5-hour exposure) spectra of the SN position and the three star-forming regions, which are at a similar redshift. The FORS spectrum at +300 days shows no trace of supernova emission lines and we place limits on the strength of [O i] from comparisons with other Ic supernovae. The deep spectra provides a unique chance to investigate spatial variations in the host star-formation activity and metallicity. The specific star-formation rate is similar in all three components, as is the presence of a young stellar population. However, the position of LSQ14mo exhibits a lower metallicity, with 12 + log(O/H) = 8.2 in both the R23 and N2 scales (corresponding to ∼ 0.3 Z ). We propose that the three bright regions in the host system are interacting, which thus triggers star-formation and forms young stellar populations


5) Present-day mass-metallicity relation for galaxies using a new electron-temperature method

Robert M. Yates, Patricia Schady, Ting-Wan Chen, Tassilo Schweyer, Philip Wiseman | 2019, A&A, accepted, arXiv:1901.02890

We present a study of electron temperatures (Te) and gas-phase oxygen abundances (ZTe) for galaxies in the local Universe (z < 0.25). Our sample comprises spectra from a total of 264 emission-line systems, ranging from individual HII regions to whole galaxies, and including 23 composite HII regions in predominantly ‘main-sequence’ galaxies from the MaNGA survey. We utilise 130 of these systems with directly measurable T(OII) to derive a new metallicity dependent T(OIII) – T(OII) relation that provides a better representation of our varied data set than existing relations from the literature. Importantly, we find that all the T(OIII) – T(OII) relations considered here intrinsically under-estimate ZTe at low O++/O+ by up to 0.6 dex, and provide an empirical correction based on strong-emission lines to account for this bias when using our relation. Our new Te method therefore allows accurate metallicities (1sigma = 0.08 dex) to be derived for any low-redshift system with an [OIII]4363 line detection, regardless of its physical size or ionisation state. This new Te method is then used to form the mass – metallicity relation (MZR) for a set of 118 local star-forming galaxies that is not strongly biased to starbursts. Our new MZR is in very good agreement with those formed from direct measurements of metal recombination lines and blue supergiant absorption lines, in contrast to most other Te-based and strong-line-based MZRs. Our new Te method therefore provides an accurate and precise way of obtaining ZTe for a large and diverse range of star-forming systems in the local Universe.


8) Superluminous supernova progenitors have a half-solar metallicity threshold

Chen, Ting-Wan, Smartt, Stephen J., Yates, Robert M., et al., 2017, MNRAS, 470, 3566

Host galaxy properties provide strong constraints on the stellar progenitors of superluminous supernovae. By comparing a sample of 19 low-redshift (z < 0.3) superluminous supernova hosts to galaxy populations in the local Universe, we show that sub-solar metallicities seem to be a requirement. All superluminous supernovae in hosts with high measured gas-phase metallicities are found to explode at large galactocentric radii, indicating that the metallicity at the explosion site is likely lower than the integrated host value. We found that superluminous supernova hosts do not always have star formation rates higher than typical star-forming galaxies of the same mass. However, we confirm that high absolute specific star formation rates are a feature of superluminous supernova host galaxies, but interpret this as simply a consequence of the anticorrelation between gas-phase metallicity and specific star formation rate and the requirement of on-going star formation to produce young, massive stars greater than ∼10-20 M⊙. Based on our sample, we propose an upper limit of ˜ 0.5 Z⊙ for forming superluminous supernova progenitors (assuming an N2 metallicity diagnostic and a solar oxygen abundance of 8.69). Finally, we show that if magnetar powering is the source of the extreme luminosity, then the required initial spins appear to be correlated with metallicity of the host galaxy. This correlation needs further work, but if it applies, it is a powerful link between the supernova parameters and nature of the progenitor population.


9) Gas inflow and outflow in an interacting high-redshift galaxy: The remarkable host environment of GRB 080810 at z = 3.35

Wiseman, P., Perley, D., Schady, P., Prochaska, J., de Ugarte Postigo, A., Krühler, T., Yates, R. M.; Greiner, J., 2017, A&A, 607, 107

We reveal multiple components of an interacting galaxy system at z ≈ 3.35 through a detailed analysis of the exquisite high-resolution Keck/HIRES spectrum of the afterglow of a gamma-ray burst (GRB). Through Voigt-profile fitting of absorption lines from the Lyman series, we constrain the neutral hydrogen column density to NH I ≤ 1018.35 cm-2 for the densest of four distinct systems at the host redshift of GRB 080810, which is among the lowest NH I ever observed in a GRB host, even though the line of sight passes within a projected 5 kpc of the galaxy centres. By detailed analysis of the corresponding metal absorption lines, we derive chemical, ionic, and kinematic properties of the individual absorbing systems, and thus build a picture of the host as a whole. Striking differences between the systems imply that the line of sight passes through several phases of gas: the star-forming regions of the GRB host; enriched material in the form of a galactic outflow; the hot and ionised halo of a second interacting galaxy falling towards the host at a line-of-sight velocity of 700 km s-1; and a cool metal-poor cloud that may represent one of the best candidates yet for the inflow of metal-poor gas from the intergalactic medium.


10) SDSS IV MaNGA - Properties of AGN Host Galaxies

Sanchez S. F., et al., 2018, RMxAA, 54, 217

We present the characterization of the main properties of a sample of 98 AGN host galaxies, both type-II and type-I, in comparison with those of ≍2700 non-active galaxies observed by the MaNGA survey. We found that AGN hosts are morphologically early-type or early-spirals. AGN hosts are, on average, more massive, more compact, more centrally peaked and more pressure-supported systems. They are located in the intermediate/transition region between starforming and non-star-forming galaxies (i.e., the so-called green valley). We consider that they are in the process of halting/quenching the star formation. The analysis of the radial distributions of different properties shows that the quenching happens from inside-out involving both a decrease of the effciency of the star formation and a deficit of molecular gas. The data-products of the current analysis are distributed as a Value Added Catalog within the SDSS-DR14.


11) A new method to quantify environment and model ram-pressure stripping in N-body simulations

Ayromlou M., Nelson D., Yates R. M., Kauffmann G., White S. D. M., 2019, MNRAS, 487, 4313

We introduce a local background environment (LBE) estimator that can be measured in and around every galaxy or its dark matter subhalo in high-resolution cosmological simulations. The LBE is designed to capture the influence of environmental effects such as ram-pressure stripping (RPS) on the formation and evolution of galaxies in semi-analytical models. We define the LBE directly from the particle data within an adaptive spherical shell, and devise a Gaussian mixture estimator to separate background particles from previously unidentified subhalo particles. Analysing the LBE properties, we find that the LBE of satellite galaxies is not at rest with respect to their host halo, in contrast to typical assumptions. The orientations of the velocities of a subhalo and its LBE are well aligned in the outer infall regions of haloes, but decorrelated near halo centre. Significantly, there is no abrupt change in LBE velocity or density at the halo virial radius. This suggests that stripping should also happen beyond this radius. Therefore, we use the time-evolving LBE of galaxies to develop a method to better account for RPS of hot gas within the Munich semi-analytical model, L-GALAXIES. Overall, our new approach results in a significant increase in gas stripping across cosmic time. Central galaxies, as well as satellites beyond the virial radius, can lose a significant fraction of their hot halo gas. As a result, the gas fractions and star formation rates of satellite galaxies are suppressed relative to the fiducial model, although the stellar masses and global stellar mass functions are largely unchanged.


12) Detailed dust modelling in the L-GALAXIES semi-analytic model of galaxy formation

Vijayan A. P., Clay S. J., Thomas P. A., Yates R. M., Wilkins S. M., Henriques B. M., 2019, MNRAS, 489, 4072

We implement a detailed dust model into the L-Galaxies semi-analytical model which includes: injection of dust by type II and type Ia supernovae (SNe) and AGB stars; grain growth in molecular clouds; and destruction due to supernova-induced shocks, star formation, and reheating. Our grain growth model follows the dust content in molecular clouds and the inter-cloud medium separately, and allows growth only on pre-existing dust grains. At early times, this can make a significant difference to the dust growth rate. Above z  8, type II SNe are the primary source of dust, whereas below z  8, grain growth in molecular clouds dominates, with the total dust content being dominated by the latter below z  6. However, the detailed history of galaxy formation is important for determining the dust content of any individual galaxy. We introduce a fit to the dust-to-metal (DTM) ratio as a function of metallicity and age, which can be used to deduce the DTM ratio of galaxies at any redshift. At z  3, we find a fairly flat mean relation between metallicity and the DTM, and a positive correlation between metallicity and the dust-to-gas (DTG) ratio, in good agreement with the shape and normalization of the observed relations. We also match the normalization of the observed stellar mass-dust mass relation over the redshift range of 0-4, and to the dust mass function at z = 0. Our results are important in interpreting observations on the dust content of galaxies across cosmic time, particularly so at high redshift.


13) L-GALAXIES 2020: Spatially resolved cold gas phases, star formation and chemical enrichment in galactic discs

Henriques, Bruno M. B.; Yates, Robert M.; Fu, Jian; Guo, Qi; Kauffmann, Guinevere; Srisawat, Chaichalit; Thomas, Peter A.; White, Simon D. M., 2019, MNRAS, accepted

We have updated the Munich galaxy formation model, L-GALAXIES, to follow the radial distributions of stars and atomic and molecular gas in galaxy discs. We include an H2-based star-formation law, as well as a detailed chemical-enrichment model with explicit mass-dependent delay times for SN-II, SN-Ia and AGB stars. Information about the star formation, feedback and chemical-enrichment histories of discs is stored in 12 concentric rings. The new model retains the success of its predecessor in reproducing the observed evolution of the galaxy population, in particular, stellar mass functions and passive fractions over the redshift range 0 ≤ z ≤ 3 and mass range 8 ≤ log (M*/{ Msun) ≤ 12, the black hole-bulge mass relation at z = 0, galaxy morphology as a function of stellar mass and the mass-metallicity relations of both stellar and gas components. In addition, its detailed modelling of the radial structure of discs allows qualitatively new comparisons with observation, most notably with the relative sizes and masses of the stellar, atomic and molecular components in discs. Good agreement is found with recent data. Comparison of results obtained for simulations differing in mass resolution by more than two orders of magnitude shows that all important distributions are numerically well converged even for this more detailed model. An examination of metallicity and surface-density gradients in the stars and gas indicates that our new model, with star formation, chemical enrichment and feedback calculated self-consistently on local disc scales, reproduces some but not all of the trends seen in recent many-galaxy IFU surveys.