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The newly updated GIZMO and Simba based simulation, Simba-C , with its new stellar feedback, chemical enrichment, and recalibrated AGN feedback, allows for a detailed study of the intragroup medium X-ray properties. We discuss the impact of various physical mechanisms, e.g. stellar and AGN feedback, and chemical enrichment, on the composition and the global scaling relations of nearby galaxy groups. We also study the evolution (z = 2 to 0) of the global properties for the |$1\, \mathrm{keV}$| temperature groups. Simba-C shows improved consistent matching with the observations of all X-ray scaling relations compared to Simba. It is well known that AGN feedback has a significant influence on L X, 0.5–2.0– T spec, corr, S 500/2500– T spec, corr, and gas mass fractions, with our Simba-C results consistent with it. Our recalibrated AGN feedback strength also showed an additional improvement in gas entropy, which now aligns with CLoGS observations. The updated stellar feedback and chemical enrichment model is shown to play an important role in our understanding of the chemical abundance ratios and their evolution within galaxy groups. In particular, we find that Simba-C produces an increase in the amount of heavier elements (specifically Si and Fe) relative to O, compared to Simba. [ABSTRACT FROM AUTHOR]

Edge-on galaxies act as the best laboratories to understand the origin of thin and thick discs in galaxies. Measurement of spatially resolved stellar population properties in such galaxies, particularly age, metallicity, and [α/Fe], are crucial to understanding the formation and evolution of disc galaxies. Such measurements are made possible from stellar population model fits to deep integral field spectroscopic (IFU) observations of resolved galaxies. We utilize archival MUSE IFU observations of the edge-on galaxy ESO 544-27 to uncover the formation history of its thin and thick discs through its stellar populations. We find the thin disc of the galaxy is dominated by an old (>9 Gyr) low [α/Fe] metal-rich stellar population. Its outer thick disc is dominated by an old (>9 Gyr) high [α/Fe] metal-rich component that should have formed with higher star formation efficiency than the Milky Way thick disc. We thus find [α/Fe] dichotomy in ESO 544-27 with its thin and thick discs dominated by low and high [α/Fe] stellar populations, respectively. However, we also find a metal-rich younger (<2 Gyr old) stellar population in ESO 544-27. The galaxy was nearly quenched until its star formation was reignited recently first in the outer and inner thick disc (∼1 Gyr ago) and then in the thin disc (∼600 Myr ago). We thus find that both the low [α/Fe] thin and high [α/Fe] thick discs of ESO 544-27 are inhabited primarily by similarly old metal-rich stellar populations, a contrast to that of other galaxies with known thin and thick disc stellar population properties. [ABSTRACT FROM AUTHOR]

Metallicity is a fundamental physical property that strongly constrains galaxy formation and evolution. The formation of stars in galaxies is suppressed by the energy released from supernova explosions and can be enhanced by metal production. In order to understand the impact of this supernova feedback, we compare four different feedback methods, ejecting energy in thermal, kinetic, stochastic, and mechanical forms, into our self-consistent cosmological chemodynamical simulations. To minimize other uncertainties, we use the latest nucleosynthesis yields that can reproduce the observed elemental abundances of stars in the Milky Way. For each method, we predict the evolution of stellar and gas-phase metallicities as a function of galaxy mass, i.e. the mass–metallicity relations. We then find that the mechanical feedback can give the best match to a number of observations up to redshift z ∼ 3, although the predicted gas-phase metallicities seem to be higher than those observed at z ≳ 1. The feedback modelling can be further constrained by the metallicities in distant galaxies with the JWST and those of a large sample with ongoing and future spectroscopic surveys. [ABSTRACT FROM AUTHOR]

We introduce a new chemical enrichment and stellar feedback model into GIZMO , using the SIMBA sub-grid models as a base. Based on the state-of-the-art chemical evolution model of Kobayashi et al. SIMBA-C tracks 34 elements from H→Ge and removes SIMBA 's instantaneous recycling approximation. Furthermore, we make some minor improvements to SIMBA 's base feedback models. SIMBA-C provides significant improvements on key diagnostics such as the knee of the z  = 0 galaxy stellar mass function, the faint end of the main sequence, and the ability to track black holes in dwarf galaxies. SIMBA-C also matches better with recent observations of the mass–metallicity relation at z  = 0, 2. By not assuming instantaneous recycling, SIMBA-C provides a much better match to galactic abundance ratio measures such as [O/Fe] and [N/O]. SIMBA-C thus opens up new avenues to constrain feedback models using detailed chemical abundance measures across cosmic time. [ABSTRACT FROM AUTHOR]

We present a multizone galactic chemical evolution (GCE) model for the Milky Way that takes the most recently updated yields of major nucleosynthesis channels into account. It incorporates physical processes commonly found in previous GCE models like gas feedback from supernovae and star formation, the radial flow of gas in the disc, and the infall of fresh gas, along with stellar scattering processes like radial migration. We individually analyse the effect of different physical processes present in our model on the observed properties of the Galaxy. The radial flow of gas in the disc plays an important role in establishing the radial gradient for [Fe/H] in the low-[α/Fe] sequence. Our model with one episode of smooth gas infall and constant star formation efficiency is capable of reproducing the observed ([Fe/H], [α/Fe]) distribution of stars at different (R , | z |) positions in the Milky Way. Our results point to the rapid evolution of [α/Fe] after the onset of Type Ia supernovae and a high star formation rate during the formation of the high-[α/Fe] sequence as the origin of dual peaks in [α/Fe]. A secondary infall is unnecessary to reproduce the [α/Fe] gap and chemical spread in the disc in our model. We additionally compare the median age for various mono-abundance populations and the age–metallicity relation at different (R , | z |) positions from our fiducial model to observations. We discuss our results in relation to other related work in detail. [ABSTRACT FROM AUTHOR]

While modeling the galactic chemical evolution (GCE) of stable elements provides insights to the formation history of the Galaxy and the relative contributions of nucleosynthesis sites, modeling the evolution of short-lived radioisotopes (SLRs) can provide supplementary timing information on recent nucleosynthesis. To study the evolution of SLRs, we need to understand their spatial distribution. Using a three-dimensional GCE model, we investigated the evolution of four SLRs: 53Mn, 60Fe, 182Hf, and 244Pu with the aim of explaining detections of recent (within the last ≈1–20 Myr) deposition of live 53Mn, 60Fe, and 244Pu of extrasolar origin into deep-sea reservoirs. We find that core-collapse supernovae are the dominant propagation mechanism of SLRs in the Galaxy. This results in the simultaneous arrival of these four SLRs on Earth, although they could have been produced in different astrophysical sites, which can explain why live extrasolar 53Mn, 60Fe, and 244Pu are found within the same, or similar, layers of deep-sea sediments. We predict that 182Hf should also be found in such sediments at similar depths. [ABSTRACT FROM AUTHOR]

Thanks to the long-term collaborations between nuclear and astrophysics, we have good understanding on stellar nucleosynthesis, except for the elements around Ti and some neutron-capture elements. From the comparison between observations and Galactic chemical evolution models, it is necessary to have the rapid neutron-capture process associated with core-collapse supernovae, although the explosion mechanism is unknown. The impact of rotating massive stars is also shown in this paper. Many of the key elements can be exclusively obtained in the UV, and therefore without UV spectra it would not be possible to fully understand the origin of elements in the universe. [ABSTRACT FROM AUTHOR]

In this work, we have implemented a detailed physical model of galaxy chemical enrichment into the Astraeus (seminumerical rAdiative tranSfer coupling of galaxy formaTion and Reionization in N -body dark matter simUlationS) framework which couples galaxy formation and reionization in the first billion years. Simulating galaxies spanning over 2.5 orders of magnitude in halo mass with |$M_{\rm h} \sim 10^{8.9}{-}10^{11.5}\,{\rm M_\odot}$| (⁠|$M_{\rm h} \sim 10^{8.9}{-}10^{12.8}\rm M_\odot$|⁠) at z ∼ 10 (5), we find: (i) smooth accretion of metal-poor gas from the intergalactic medium (IGM) plays a key role in diluting the interstellar medium interstellar medium metallicity which is effectively restored due to self-enrichment from star formation; (ii) a redshift averaged gas-mass loading factor that depends on the stellar mass as |$\eta _{\rm g} \approx 1.38 ({M_*}/{10^{10}\, {\rm \rm M_\odot }})^{-0.43}$|⁠ ; (iii) the mass–metallicity relation is already in place at z ∼ 10 and shows effectively no redshift evolution down to z ∼ 5; (iv) for a given stellar mass, the metallicity decreases with an increase in the star formation rate (SFR); (v) the key properties of the gas-phase metallicity (in units of 12 + log(O/H), stellar mass, SFR and redshift are linked through a high-redshift fundamental plane of metallicity (HFPZ) for which we provide a functional form; (vi) the mass–metallicity–SFR relations are effectively independent of the reionization radiative feedback model for |$M_* {\,\, \buildrel\gt \over \sim \,\,}10^{6.5}\rm M_\odot$| galaxies; (vii) while low-mass galaxies (⁠|$M_{\rm h} {\,\, \buildrel\lt \over \sim \,\,}10^9\,\rm M_\odot$|⁠) are the key contributors to the metal budget of the IGM at early times, higher mass haloes provide about 50 per cent of the metal budget at lower redshifts. [ABSTRACT FROM AUTHOR]

We obtain a magnitude-limited sample of Andromeda (M 31) disc PNe with chemical abundance estimated through the direct detection of the [O  iii ] 4363 Å line. This leads to 205 and 200 PNe with oxygen and argon abundances, respectively. We find that high- and low-extinction M 31 disc PNe have statistically distinct argon and oxygen abundance distributions. In the radial range of 2−30 kpc, the older low-extinction disc PNe are metal-poorer on average with a slightly positive radial oxygen abundance gradient (0.006 ± 0.003 dex kpc−1) and slightly negative for argon (−0.005 ± 0.003 dex kpc−1), while the younger high-extinction disc PNe are metal-richer on average with steeper radial abundance gradients for both oxygen (−0.013 ± 0.006 dex kpc−1) and argon (−0.018 ± 0.006 dex kpc−1), similar to the gradients computed for the M 31 H  ii regions. The M 31 disc abundance gradients are consistent with values computed from major merger simulations, with the majority of the low-extinction PNe being the older pre-merger disc stars in the thicker disc, and the majority of the high-extinction PNe being younger stars in the thin disc, formed during and after the merger event. The chemical abundance of the M 31 thicker disc has been radially homogenized because of the major merger. Accounting for disc scale lengths, the positive radial oxygen abundance gradient of the M 31 thicker disc is in sharp contrast to the negative one of the MW thick disc. However, the thin discs of the MW and M 31 have remarkably similar negative oxygen abundance gradients. [ABSTRACT FROM AUTHOR]

Thanks to the long-term collaborations between nuclear and astrophysics, we have good understanding on the origin of elements in the universe, except for the elements around Ti and some neutron-capture elements. From the comparison between observations of nearby stars and Galactic chemical evolution models, a rapid neutron-capture process associated with core-collapse supernovae is required. The production of C, N, F and some minor isotopes depends on the rotation of massive stars, and the observations of distant galaxies with ALMA indicate rapid cosmic enrichment. It might be hard to find very metal-poor or Population III (and dust-free) galaxies at very high redshifts even with JWST. [ABSTRACT FROM AUTHOR]

We present a comparison of the nitrogen-to-oxygen ratio (N/O) in 37 high-redshift galaxies at z ∼ 2 taken from the KMOS Lensed Emission Lines and VElocity Review (KLEVER) Survey with a comparison sample of local galaxies, taken from the Sloan Digital Sky Survey (SDSS). The KLEVER sample shows only a mild enrichment in N/O of +0.1 dex when compared to local galaxies at a given gas-phase metallicity (O/H), but shows a depletion in N/O of −0.35 dex when compared at a fixed stellar mass (M *). We find a strong anticorrelation in local galaxies between N/O and SFR in the M *–N/O plane, similar to the anticorrelation between O/H and SFR found in the mass–metallicity relation (MZR). We use this anticorrelation to construct a fundamental nitrogen relation (FNR), analogous to the fundamental metallicity relation (FMR). We find that KLEVER galaxies are consistent with both the FMR and the FNR. This suggests that the depletion of N/O in high- z galaxies when considered at a fixed M * is driven by the redshift evolution of the mass–metallicity relation in combination with a near redshift-invariant N/O–O/H relation. Furthermore, the existence of an fundamental nitrogen relation suggests that the mechanisms governing the fundamental metallicity relation must be probed by not only O/H, but also N/O, suggesting pure-pristine gas inflows are not the primary driver of the FMR, and other properties such as variations in galaxy age and star formation efficiency must be important. [ABSTRACT FROM AUTHOR]

We present the third and final data release of the K2 Galactic Archaeology Program (K2 GAP) for Campaigns C1–C8 and C10–C18. We provide asteroseismic radius and mass coefficients, κR and κM, for ∼19,000 red giant stars, which translate directly to radius and mass given a temperature. As such, K2 GAP DR3 represents the largest asteroseismic sample in the literature to date. K2 GAP DR3 stellar parameters are calibrated to be on an absolute parallactic scale based on Gaia DR2, with red giant branch and red clump evolutionary state classifications provided via a machine-learning approach. Combining these stellar parameters with GALAH DR3 spectroscopy, we determine asteroseismic ages with precisions of ∼20%–30% and compare age-abundance relations to Galactic chemical evolution models among both low- and high-α populations for α, light, iron-peak, and neutron-capture elements. We confirm recent indications in the literature of both increased Ba production at late Galactic times as well as significant contributions to r-process enrichment from prompt sources associated with, e.g., core-collapse supernovae. With an eye toward other Galactic archeology applications, we characterize K2 GAP DR3 uncertainties and completeness using injection tests, suggesting that K2 GAP DR3 is largely unbiased in mass/age, with uncertainties of 2.9% (stat.) ± 0.1% (syst.) and 6.7% (stat.) ± 0.3% (syst.) in κR and κM for red giant branch stars and 4.7% (stat.) ± 0.3% (syst.) and 11% (stat.) ± 0.9% (syst.) for red clump stars. We also identify percent-level asteroseismic systematics, which are likely related to the time baseline of the underlying data, and which therefore should be considered in TESS asteroseismic analysis. [ABSTRACT FROM AUTHOR]

The characteristics of the stellar populations in the Galactic bulge inform and constrain the Milky Way's formation and evolution. The metal-poor population is particularly important in light of cosmological simulations, which predict that some of the oldest stars in the Galaxy now reside in its centre. The metal-poor bulge appears to consist of multiple stellar populations that require dynamical analyses to disentangle. In this work, we undertake a detailed chemodynamical study of the metal-poor stars in the inner Galaxy. Using R ∼ 20 000 VLT/GIRAFFE spectra of 319 metal-poor (−2.55 dex ≤ [Fe/H] ≤ 0.83 dex, with |$\overline{\rm {[Fe/H]}}$| = −0.84 dex) stars, we perform stellar parameter analysis and report 12 elemental abundances (C, Na, Mg, Al, Si, Ca, Sc, Ti, Cr, Mn, Zn, Ba, and Ce) with precisions of ≈0.10 dex. Based on kinematic and spatial properties, we categorize the stars into four groups, associated with the following Galactic structures: the inner bulge, the outer bulge, the halo, and the disc. We find evidence that the inner and outer bulge population is more chemically complex (i.e. higher chemical dimensionality and less correlated abundances) than the halo population. This result suggests that the older bulge population was enriched by a larger diversity of nucleosynthetic events. We also find one inner bulge star with a [Ca/Mg] ratio consistent with theoretical pair-instability supernova yields and two stars that have chemistry consistent with globular cluster stars. [ABSTRACT FROM AUTHOR]

We propose a new mission called Space Project for Astrophysical and Cosmological Exploration (SPACE) as part of the ESA long term planning Voyage 2050 programme. SPACE will study galaxy evolution at the earliest times, with the key goals of charting the formation of the heavy elements, measuring the evolution of the galaxy luminosity function, tracing the build-up of stellar mass in galaxies over cosmic time, and finding the first super-massive black holes (SMBHs) to form. The mission will exploit a unique region of the parameter space, between the narrow ultra-deep surveys with HST and JWST, and shallow wide-field surveys such as the Roman Space Telescope and EUCLID, and should yield by far the largest sample of any current or planned mission of very high redshift galaxies at z > 10 which are sufficiently bright for detailed follow-up spectroscopy. Crucially, we propose a wide-field spectroscopic near-IR + mid-IR capability which will greatly enhance our understanding of the first galaxies by detecting and identifying a statistical sample of the first galaxies and the first supermassive black holes, and to chart the metal enrichment history of galaxies in the early Universe – potentially finding signatures of the very first stars to form from metal-free primordial gas. The wide-field and wavelength range of SPACE will also provide us a unique opportunity to study star formation by performing a wide survey of the Milky Way in the near-IR + mid-IR. This science project can be enabled either by a stand-alone ESA-led M mission or by an instrument for an L mission (with ESA and/or NASA, JAXA and other international space agencies) with a wide-field (sub-)millimetre capability at λ > 500 μm. [ABSTRACT FROM AUTHOR]

Radioactive 26Al is an excellent tracer for metal ejection in the Milky Way, and can provide a direct constraint on the modelling of supernova feedback in galaxy evolution. Gamma-ray observations of the 26Al decay line have found high velocities and hence require a significant fraction of the Galactic 26Al in the hot component. At the same time, meteoritic data combined with simulation results suggest that a significant amount of 26Al makes its way into stars before decay. We investigated the distribution into hot and cold channels with a simulation of a Milky-Way-like galaxy with massive-star feedback in superbubbles and with ejecta traced by 26Al. About 30–40 per cent of the ejecta remain hot, with typical cooling times of the order Gyr. 26Al traces the footpoints of a chimney-fed outflow that mixes metals turbulently into the halo of the model galaxy on a scale of at least 50 kpc. The rest diffuses into cold gas ≲ 104 K, and may therefore be quickly available for star formation. We discuss the robustness of the result by comparison to a simulation with a different global flow pattern. The branching ratio into hot and cold components is comparable to that of longer term average results from chemical evolution modelling of galaxies, clusters, and the intracluster medium. [ABSTRACT FROM AUTHOR]

To reach a deeper understanding of the origin of elements in the periodic table, we construct Galactic chemical evolution (GCE) models for all stable elements from C (A = 12) to U (A = 238) from first principles, i.e., using theoretical nucleosynthesis yields and event rates of all chemical enrichment sources. This enables us to predict the origin of elements as a function of time and environment. In the solar neighborhood, we find that stars with initial masses of M > 30M⊙ can become failed supernovae if there is a significant contribution from hypernovae (HNe) at M ∼ 20–50M⊙. The contribution to GCE from super-asymptotic giant branch (AGB) stars (with M ∼ 8–10M⊙ at solar metallicity) is negligible, unless hybrid white dwarfs from low-mass super-AGB stars explode as so-called Type Iax supernovae, or high-mass super-AGB stars explode as electron-capture supernovae (ECSNe). Among neutron-capture elements, the observed abundances of the second (Ba) and third (Pb) peak elements are well reproduced with our updated yields of the slow neutron-capture process (s-process) from AGB stars. The first peak elements (Sr, Y, Zr) are sufficiently produced by ECSNe together with AGB stars. Neutron star mergers can produce rapid neutron-capture process (r-process) elements up to Th and U, but the timescales are too long to explain observations at low metallicities. The observed evolutionary trends, such as for Eu, can well be explained if ∼3% of 25–50M⊙ HNe are magneto-rotational supernovae producing r-process elements. Along with the solar neighborhood, we also predict the evolutionary trends in the halo, bulge, and thick disk for future comparison with Galactic archeology surveys. [ABSTRACT FROM AUTHOR]

Star formation in galaxies relies on the availability of cold, dense gas, which, in turn, relies on factors internal and external to the galaxies. In order to provide a simple model for how star formation is regulated by various physical processes in galaxies, we analyse data at redshift z = 0 from a hydrodynamical cosmological simulation that includes prescriptions for star formation and stellar evolution, active galactic nuclei, and their associated feedback processes. This model can determine the star formation rate (SFR) as a function of galaxy stellar mass, gas mass, black hole mass, and environment. We find that gas mass is the most important quantity controlling star formation in low-mass galaxies, and star-forming galaxies in dense environments have higher SFR than their counterparts in the field. In high-mass galaxies, we find that black holes more massive than ∼ 107.5 M⊙ can be triggered to quench star formation in their host; this mass scale is emergent in our simulations. Furthermore, this black hole mass corresponds to a galaxy bulge mass ∼ 2 × 1010 M⊙, consistent with the mass at which galaxies start to become dominated by early types (∼ 3 × 1010 M⊙, as previously shown in observations by Kauffmann et al.). Finally, we demonstrate that our model can reproduce well the SFR measured from observations of galaxies in the Galaxy And Mass Assembly and Arecibo Legacy Fast ALFA surveys. [ABSTRACT FROM AUTHOR]

We investigate a sample of 40 local, main-sequence, edge-on disc galaxies using integral field spectroscopy with the Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy Survey to understand the link between properties of the extraplanar gas and their host galaxies. The kinematics properties of the extraplanar gas, including velocity asymmetries and increased dispersion, are used to differentiate galaxies hosting large-scale galactic winds from those dominated by the extended diffuse ionized gas. We find rather that a spectrum of diffuse gas-dominated to wind-dominated galaxies exist. The wind-dominated galaxies span a wide range of star formation rates (SFRs; -1 ≲ log?(SFR/M⊙?yr-1) ≲ 0.5) across the whole stellar mass range of the sample (8.5 ≲ log (M*/M⊙) ≲ 11). The wind galaxies also span a wide range in SFR surface densities (10-3-10-1.5?M⊙?yr-1?kpc-2) that is much lower than the canonical threshold of 0.1?M⊙?yr-1?kpc-2. The wind galaxies on average have higher SFR surface densities and higher HδA values than those without strong wind signatures. The enhanced HδA indicates that bursts of star formation in the recent past are necessary for driving large-scale galactic winds. We demonstrate with Sloan Digital Sky Survey data that galaxies with high SFR surface density have experienced bursts of star formation in the recent past. Our results imply that the galactic winds revealed in our study are indeed driven by bursts of star formation, and thus probing star formation in the time domain is crucial for finding and understanding galactic winds. [ABSTRACT FROM AUTHOR]

We showthat feedback from active galactic nuclei (AGN) plays an essential role in reproducing the down-sizing phenomena, namely: the colour--magnitude relation; specific star formation rates; and the α enhancement of early-type galaxies. In our AGN model, black holes originate from Population III stars, in contrast to the merging scenario of previous works. In this paper, we show how the properties of present-day galaxies in cosmological chemo-hydrodynamical simulations change when we include our model for AGN feedback. Massive galaxies become redder, older, less massive, less compact, and show greater α enhancement than their counterparts without AGN. Since we reproduce the black hole mass and galaxy mass relation, smaller galaxies do not host a supermassive black hole and their star formation history is affected very little, but they can get external enrichment from nearby AGN depending on their environment. Nonetheless, the metallicity change is negligible, and the mass--metallicity relations, which are mainly generated by supernova feedback at the first starburst, are preserved. [ABSTRACT FROM AUTHOR]

BSTRACT [ABSTRACT FROM AUTHOR]

Radioactive nuclei are the key to understanding the circumstances of the birth of our Sun because meteoritic analysis has proven that many of them were present at that time. Their origin, however, has been so far elusive. The ERC-CoG-2016 RADIOSTAR project is dedicated to investigating the production of radioactive nuclei by nuclear reactions inside stars, their evolution in the Milky Way Galaxy, and their presence in molecular clouds. So far, we have discovered that: (i) radioactive nuclei produced by s l o w ( 107 Pd and 182 Hf) and r a p i d ( 129 I and 247 Cm) neutron captures originated from stellar sources —asymptotic giant branch (AGB) stars and compact binary mergers, respectively—within the galactic environment that predated the formation of the molecular cloud where the Sun was born; (ii) the time that elapsed from the birth of the cloud to the birth of the Sun was of the order of 10 7 years, and (iii) the abundances of the very short-lived nuclei 26 Al, 36 Cl, and 41 Ca can be explained by massive star winds in single or binary systems, if these winds directly polluted the early Solar System. Our current and future work, as required to finalise the picture of the origin of radioactive nuclei in the Solar System, involves studying the possible origin of radioactive nuclei in the early Solar System from core-collapse supernovae, investigating the production of 107 Pd in massive star winds, modelling the transport and mixing of radioactive nuclei in the galactic and molecular cloud medium, and calculating the galactic chemical evolution of 53 Mn and 60 Fe and of the p-process isotopes 92 Nb and 146 Sm. [ABSTRACT FROM AUTHOR]

We simulate the chemodynamical evolution of elliptical galaxies using our GRAPE-SPH code. We succeed in reproducing the observed variety of the radial metallicity gradients, from which we discuss the origin of elliptical galaxies. [ABSTRACT FROM AUTHOR]

Star formation in galaxies relies on the availability of cold, dense gas, which, in turn, relies on factors internal and external to the galaxies. In order to provide a simple model for how star formation is regulated by various physical processes in galaxies, we analyse data at redshift z = 0 from a hydrodynamical cosmological simulation that includes prescriptions for star formation and stellar evolution, active galactic nuclei, and their associated feedback processes. This model can determine the star formation rate (SFR) as a function of galaxy stellar mass, gas mass, black hole mass, and environment. We find that gas mass is the most important quantity controlling star formation in low-mass galaxies, and star-forming galaxies in dense environments have higher SFR than their counterparts in the field. In high-mass galaxies, we find that black holes more massive than ∼ 107.5 M⊙ can be triggered to quench star formation in their host; this mass scale is emergent in our simulations. Furthermore, this black hole mass corresponds to a galaxy bulge mass ∼ 2 × 1010 M⊙, consistent with the mass at which galaxies start to become dominated by early types (∼ 3 × 1010 M⊙, as previously shown in observations by Kauffmann et al.). Finally, we demonstrate that our model can reproduce well the SFR measured from observations of galaxies in the Galaxy And Mass Assembly and Arecibo Legacy Fast ALFA surveys. [ABSTRACT FROM AUTHOR]