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We measure the broad impact of galaxy structure on galaxy formation by examining the ongoing star formation and integrated star formation history as revealed through the stellar masses of galaxies at z < 7 based on JWST CEERS data from the Extended Groth Strip (EGS). Using the morphological catalog of 3965 visually classified JWST galaxies from Ferreira et al. (2023), we investigate the evolution of stars, and when they form, as a function of morphological type as well as galaxies classified as passive and starburst through spectral energy distributions. Although disc galaxies dominate the structures of galaxies at z < 7, we find that these discs are in general either 'passive', or on the main sequence of star formation, and do not contain a large population of starburst galaxies. We also find no significant correlation between morphological type and the star formation rate or colours of galaxies at z < 7. In fact, we find that the morphologically classified 'spheroids' tend to be blue and are not found to be predominately passive systems at z > 1.5. We also find that the stellar mass function for disc galaxies does not evolve significantly during this time, whereas other galaxy types, such as the peculiar population, evolve dramatically, declining at lower redshifts. This indicates that massive peculiars are more common at higher redshifts. We further find that up to z ∼ 7, the specific star formation rate (sSFR) does not vary with visual morphology, but strongly depends on stellar mass and internal galaxy mass density. This demonstrates that at early epochs galaxy assembly is a mass-driven, rather than a morphologically driven process. Quenching of star formation is therefore a mass-dominated process throughout the universe's history, likely due to the presence of supermassive black holes. [ABSTRACT FROM AUTHOR]

We study the distribution and evolution of the stellar mass and the star formation rate (SFR) of the brightest group galaxies (BGGs) over 0.04 < z < 1.3 using a large sample of 407 X-ray galaxy groups selected from the COSMOS, AEGIS, and XMM-LSS fields. We compare our results with predictions from the semi-analytic models based on the Millennium simulation. In contrast to model predictions, we find that, as the Universe evolves, the stellar mass distribution evolves towards a normal distribution. This distribution tends to skew to low-mass BGGs at all redshifts implying the presence of a star-forming population of the BGGs with MS ∼ 1010.5 M⊙ which results in the shape of the stellar mass distribution deviating from a normal distribution. In agreement with the models and previous studies, we find that the mean stellar mass of BGGs grows with time by a factor of ∼2 between z = 1.3 and z = 0.1, however, the significant growth occurs above z = 0.4. The BGGs are not entirely a dormant population of galaxies, as low-mass BGGs in low-mass haloes are more active in forming stars than the BGGs in more massive haloes, over the same redshift range. We find that the average SFR of the BGGs evolves steeply with redshift and fraction of the passive BGGs increases as a function of increasing stellar mass and halo mass. Finally, we show that the specific SFR of the BGGs within haloes with M200 ≤ 1013.4 M⊙ decreases with increasing halo mass at z < 0.4. [ABSTRACT FROM AUTHOR]

The properties of galaxies in low-density regions of the universe suggest an interplay between galaxy formation and environment. However, the specific reason why this particular large-scale environment influences the evolution of galaxies remains unclear. This paper examines the properties and evolutionary paths of galaxies within cosmic voids using the Illustris TNG300 simulation. The population of void galaxies at z = 0 has a higher star formation rate, a smaller stellar-to-halo-mass ratio, higher gas metallicity, and lower stellar metallicity in comparison with non-void galaxies at fixed stellar mass. Our analysis shows that these differences are mainly due to the characteristics of galaxies classified as satellites, for which the largest differences between void and non-void samples are found. Although the mean number of mergers is similar between void and non-void samples at a fixed stellar mass, void galaxies tend to experience mergers at later times, resulting in a more recent accumulation of accreted stellar mass. While the mean net accreted mass is comparable for high-mass galaxies, low-mass void galaxies tend to exhibit higher fractions of accreted stars than non-void galaxies. This finding challenges the common notion that void galaxies predominantly experience growth with infrequent mergers or interactions. With this paper, we also publicly release our void catalogue as part of the IllustrisTNG project. [ABSTRACT FROM AUTHOR]

This article is a correction to a previous paper titled "The hot gas distribution, X-ray luminosity, and baryon budget in the L-Galaxies semi-analytic model of galaxy formation." The authors discovered an error in their calculations regarding the infall time-scale of the cool core in galaxy clusters. They mistakenly used the dynamical time-scale of the entire halo instead of the correct free-fall time-scale at the core radius. This error affects the gas cooling rate and subsequently the results of the stellar and gas components in galaxy formation. The authors provide updated results and conclusions based on the corrected calculations. [Extracted from the article]

The formation of supermassive black holes (SMBHs) in the Universe and its role in the properties of the galaxies is one of the open questions in astrophysics and cosmology. Though, traditionally, electromagnetic waves have been instrumental in direct measurements of SMBHs, significantly influencing our comprehension of galaxy formation, gravitational waves (GW) bring an independent avenue to detect numerous binary SMBHs in the observable Universe in the nano-Hertz range using the pulsar timing array observation. This brings a new way to understand the connection between the formation of binary SMBHs and galaxy formation if we can connect theoretical models with multimessenger observations namely GW data and galaxy surveys. Along these lines, we present here the first paper on this series based on romulus25 cosmological simulation on the properties of the host galaxies of SMBHs and propose on how this can be used to connect with observations of nano-Hertz GW signal and galaxy surveys. We show that the most dominant contribution to the background will arise from sources with high chirp masses which are likely to reside in low-redshift early-type galaxies with high stellar mass, largely old stellar population, and low star formation rate, and that reside at centres of galaxy groups and manifest evidence of recent mergers. The masses of the sources show a correlation with the halo mass and stellar mass of the host galaxies. This theoretical study will help in understanding the host properties of the GW sources and can help in establishing a connection with observations. [ABSTRACT FROM AUTHOR]

Modern cosmological hydrodynamical galaxy simulations provide tens of thousands of reasonably realistic synthetic galaxies across cosmic time. However, quantitatively assessing the level of realism of simulated universes in comparison to the real one is difficult. In this paper of the Extracting Reality from Galaxy Observables with Machine Learning series, we utilize contrastive learning to directly compare a large sample of simulated and observed galaxies based on their stellar-light images. This eliminates the need to specify summary statistics and allows to exploit the whole information content of the observations. We produce survey-realistic galaxy mock data sets resembling real Hyper Suprime-Cam (HSC) observations using the cosmological simulations TNG50 and TNG100. Our focus is on galaxies with stellar masses between 109 and 1012 M⊙ at z  = 0.1–0.4. This allows us to evaluate the realism of the simulated TNG galaxies in comparison to actual HSC observations. We apply the self-supervised contrastive learning method Nearest Neighbour Contrastive Learning to the images from both simulated and observed data sets (g -, r -, i -bands). This results in a 256-dimensional representation space, encoding all relevant observable galaxy properties. First, this allows us to identify simulated galaxies that closely resemble real ones by seeking similar images in this multidimensional space. Even more powerful, we quantify the alignment between the representations of these two image sets, finding that the majority (≳ 70 per cent) of the TNG galaxies align well with observed HSC images. However, a subset of simulated galaxies with larger sizes, steeper Sérsic profiles, smaller Sérsic ellipticities, and larger asymmetries appears unrealistic. We also demonstrate the utility of our derived image representations by inferring properties of real HSC galaxies using simulated TNG galaxies as the ground truth. [ABSTRACT FROM AUTHOR]

We present the 'Cosmological Jellyfish' project – a citizen-science classification program to identify jellyfish (JF) galaxies within the IllustrisTNG cosmological simulations. JF are satellite galaxies that exhibit long trailing gas features – 'tails' – extending from their stellar body. Their distinctive morphology arises due to ram-pressure stripping (RPS) as they move through the background gaseous medium. Using the TNG50 and TNG100 simulations, we construct a sample of |$\sim 80\, 000$| satellite galaxies spanning an unprecedented range of stellar masses, |$10^{8.3}{-}10^{12.3}\, \mathrm{M_\odot }$|⁠ , and host masses, |$M_\mathrm{200,c}=10^{10.4}{-}10^{14.6}\, \mathrm{M_\odot }$| back to z  = 2. Based on this sample, |$\sim 90\, 000$| galaxy images were presented to volunteers in the citizen-science Zooniverse platform, who were asked to determine whether the galaxy image resembles a JF. Based on volunteer votes, each galaxy received a score determining if it is a JF or not. This paper describes the project, the inspected satellite sample, the methodology, and the classification process that resulted in a data set of 5307 visually identified JF galaxies. We find that JF is common in nearly all group- and cluster-sized systems, with the JF fraction increasing with host mass and decreasing with satellite stellar mass. We highlight JF galaxies in three relatively unexplored regimes: low-mass hosts of |$M_\mathrm{200,c}\sim 10^{11.5}{-}10^{13}\, \mathrm{M_\odot }$|⁠ , radial positions within hosts exceeding the virial radius R 200, c, and at high redshift up to z  = 2. The full data set of our JF scores is publicly available and can be used to select and study JF galaxies in the IllustrisTNG simulations. [ABSTRACT FROM AUTHOR]

This paper presents the third data release of the INvestigating Stellar Population In RElics (INSPIRE) project, comprising 52 ultra-compact massive galaxies (UCMGs) observed with the X-Shooter spectrograph. We measure integrated stellar velocity dispersion, [Mg/Fe] abundances, ages, and metallicities for all the INSPIRE objects. We thus infer star formation histories and confirm the existence of a degree of relicness (DoR), defined in terms of the fraction of stellar mass formed by z  = 2, the time at which a galaxy has assembled 75 per cent of its mass, and the final assembly time. Objects with a high DoR assembled their stellar mass at early epochs, while low-DoR objects show a non-negligible fraction of later formed populations and hence a spread in ages and metallicities. A higher DoR correlates with larger [Mg/Fe], supersolar metallicity, and larger velocity dispersion values. The 52 UMCGs span a large range of DoR from 0.83 to 0.06, with 38 of them having formed more than 75  per cent of their mass by z  = 2. Of these, nine are extreme relics (DoR>0.7), since they formed the totality (⁠|$\gt 99~{{\ \rm per\ cent}}$|⁠) of their stellar mass by redshift z  = 2. The remaining 14 UCMGs cannot be considered relics, as they are characterized by more extended star formation histories. With INSPIRE  we built the first sizeable sample of relics outside the local Universe, up to z ∼ 0.4, increasing the number of confirmed relics by a factor of >10, and opening up an important window to explain the mass assembly of massive galaxies in the high- z Universe. [ABSTRACT FROM AUTHOR]

The current properties of globular cluster systems (GCSs) in the nearby Universe are a consequence of an evolutionary history ruled by accretion and disruption processes. The analysis of scaling relations for GCSs is crucial for understanding the relevance of different physical processes involved in their origin and subsequent survival. In this work, radial profiles are calculated for a sample of GCSs associated with nearby massive galaxies. This is supplemented with results from our previous papers, achieving a total sample of 53 GCSs with radial profiles homogeneously calculated, and spanning more than two orders of magnitude in stellar mass of the host galaxy. Scaling relations involving different parameters of the GCSs are obtained for the entire sample, and their significance in terms of different scenarios is considered. Finally, the results are analysed in the literature context. [ABSTRACT FROM AUTHOR]

The estimation of galaxy stellar masses depends on the assumed prior of the star-formation history (SFH) and spatial scale of the analysis (spatially resolved versus integrated scales). In this paper, we connect the prescription of the SFH in the spectral energy distribution (SED) fitting to spatially resolved scales (∼kpc) to shed light on the systematics involved when estimating stellar masses. Specifically, we fit the integrated photometry of ∼970 massive (log (M⋆/M⊙) = 9.8–11.5), intermediate redshift (z  = 0.5–2.0) galaxies with PROSPECTOR , assuming both exponentially declining tau model and flexible SFHs. We complement these fits with the results of spatially resolved SFH estimates obtained by pixel-by-pixel SED fitting, which assume tau models for individual pixels. These spatially resolved SFHs show a large diversity in shapes, which can largely be accounted for by the flexible SFHs with PROSPECTOR. The differences in the stellar masses from those two approaches are overall in good agreement (average difference of ∼0.07 dex). Contrarily, the simpler tau model SFHs typically miss the oldest episode of star formation, leading to an underestimation of the stellar mass by ∼0.3 dex. We further compare the derived global specific star-formation rate (sSFR), the mass-weighted stellar age (t50), and the star-formation time-scale (τSF) obtained from the different SFH approaches. We conclude that the spatially resolved scales within galaxies motivate a flexible SFH on global scales to account for the diversity of SFHs and counteract the effects of outshining of older stellar populations by younger ones. [ABSTRACT FROM AUTHOR]

This paper describes the extended data release (eDR) of the Calar Alto Legacy Integral Field Area (CALIFA) survey. It comprises science-grade quality data for 895 galaxies obtained with the Potsdam Multi Aperture Spectograph/PPak instrument at the 3.5-m telescope at the Calar Alto Observatory along the last 12 yr, using the V500 setup [3700–7500 Å, 6 Å/full-width at half-maximum (FWHM)] and the CALIFA observing strategy. It includes galaxies of any morphological type, star formation stage, a wide range of stellar masses (∼107–1012 M⊙), at an average redshift of ∼0.015 (90 per cent within 0.005 < z < 0.05). Primarily selected based on the projected size and apparent magnitude, we demonstrate that it can be volume corrected resulting in a statistically limited but representative sample of the population of galaxies in the nearby Universe. All the data were homogeneous re-reduced, introducing a set of modifications to the previous reduction. The most relevant is the development and implementation of a new cube-reconstruction algorithm that provides with an (almost) seeing-limited spatial resolution (FWHMPSF ∼ 1.0 arcsec). To illustrate the usability and quality of the data, we extracted two aperture spectra for each galaxy (central 1.5 arcsec and fully integrated), and analyse them using pyFIT3D. We obtain a set of observational and physical properties of both the stellar populations and the ionized gas, that have been compared for the two apertures, exploring their distributions as a function of the stellar masses and morphologies of the galaxies, comparing with recent results in the literature. [ABSTRACT FROM AUTHOR]

All modern galaxy formation models employ stochastic elements in their sub-grid prescriptions to discretize continuous equations across the time domain. In this paper, we investigate how the stochastic nature of these models, notably star formation, black hole accretion, and their associated feedback, that act on small (< kpc) scales, can back-react on macroscopic galaxy properties (e.g. stellar mass and size) across long (> Gyr) time-scales. We find that the scatter in scaling relations predicted by the EAGLE model implemented in the swift code can be significantly impacted by random variability between re-simulations of the same object, even when galaxies are resolved by tens of thousands of particles. We then illustrate how re-simulations of the same object can be used to better understand the underlying model, by showing how correlations between galaxy stellar mass and black hole mass disappear at the highest black hole masses (M BH > 108 M⊙), indicating that the feedback cycle may be interrupted by external processes. We find that although properties that are collected cumulatively over many objects are relatively robust against random variability (e.g. the median of a scaling relation), the properties of individual galaxies (such as galaxy stellar mass) can vary by up to 25 per cent, even far into the well-resolved regime, driven by bursty physics (black hole feedback), and mergers between galaxies. We suggest that studies of individual objects within cosmological simulations be treated with caution, and that any studies aiming to closely investigate such objects must account for random variability within their results. [ABSTRACT FROM AUTHOR]

The history of reionization is highly dependent on the ionizing properties of high-redshift galaxies. It is therefore important to have a solid understanding of how the ionizing properties of galaxies are linked to physical and observable quantities. In this paper, we use the First Light and Reionization Epoch Simulations (Flares) to study the Lyman-continuum (LyC, i.e. hydrogen-ionizing) emission of massive (⁠|$M_*\gt 10^8\, \mathrm{M_\odot }$|⁠) galaxies at redshifts z  = 5 − 10. We find that the specific ionizing emissivity (i.e. intrinsic ionizing emissivity per unit stellar mass) decreases as stellar mass increases, due to the combined effects of increasing age and metallicity. Flares predicts a median ionizing photon production efficiency (i.e. intrinsic ionizing emissivity per unit intrinsic far-UV luminosity) of |$\log _{10}(\xi _{\rm ion}\rm {/erg^{-1}Hz})=25.40^{+0.16}_{-0.17}$|⁠ , with values spanning the range |$\log _{10}(\xi _{\rm ion}\rm {/erg^{-1}Hz})=25-25.75$|⁠. This is within the range of many observational estimates, but below some of the extremes observed. We compare the production efficiency with observable properties, and find a weak negative correlation with the UV-continuum slope, and a positive correlation with the [O  iii ] equivalent width. We also consider the dust-attenuated production efficiency (i.e. intrinsic ionizing emissivity per unit dust-attenuated far-UV luminosity), and find a median of |$\log _{10}(\xi _{\rm ion}\rm {/erg^{-1}Hz})\sim 25.5$|⁠. Within our sample of |$M_*\gt 10^8\, \mathrm{M_\odot }$| galaxies, it is the stellar populations in low mass galaxies that contribute the most to the total ionizing emissivity. Active galactic nuclei (AGN) emission accounts for 10 − 20 per cent of the total emissivity at a given redshift, and extends the LyC luminosity function by ∼0.5 dex. [ABSTRACT FROM AUTHOR]

This is the first paper in our series on the combined analysis of the Dynamics and stellar Population (DynPop) for the MaNGA survey in the final SDSS Data Release 17 (DR17). Here, we present a catalogue of dynamically determined quantities for over 10 000 nearby galaxies based on integral-field stellar kinematics from the MaNGA survey. The dynamical properties are extracted using the axisymmetric Jeans Anisotropic Modelling (JAM) method, which was previously shown to be the most accurate for this kind of study. We assess systematic uncertainties using eight dynamical models with different assumptions. We use two orientations of the velocity ellipsoid: either cylindrically aligned JAMcyl or spherically aligned JAMsph. We also make four assumptions for the models' dark versus luminous matter distributions: (1) mass-follows-light, (2) free NFW dark halo, (3) cosmologically constrained NFW halo, (4) generalized NFW dark halo, i.e. with free inner slope. In this catalogue, we provide the quantities related to the mass distributions (e.g. the density slopes and enclosed mass within a sphere of a given radius for total mass, stellar mass, and dark matter mass components). We also provide the complete models which can be used to compute the full luminous and mass distribution of each galaxy. Additionally, we visually assess the qualities of the models to help with model selections. We estimate the observed scatter in the measured quantities which decreases as expected with improvements in quality. For the best data quality, we find a remarkable consistency of measured quantities between different models, highlighting the robustness of the results. [ABSTRACT FROM AUTHOR]

Galaxy populations are known to exhibit a strong colour bimodality, corresponding to blue star-forming and red quiescent subpopulations. The relative abundance of the two populations has been found to vary with stellar mass and environment. In this paper, we explore the effect of environment considering different types of measurements. We choose a sample of 49 911 galaxies with 0.05 < z < 0.18 from the Galaxy And Mass Assembly survey. We study the dependence of the fraction of red galaxies on different measures of the local environment as well as the large-scale 'geometric' environment defined by density gradients in the surrounding cosmic web. We find that the red galaxy fraction varies with the environment at fixed stellar mass. The red fraction depends more strongly on local environmental measures than on large-scale geometric environment measures. By comparing the different environmental densities, we show that no density measurement fully explains the observed environmental red fraction variation, suggesting the different measures of environmental density contain different information. We test whether the local environmental measures, when combined together, can explain all the observed environmental red fraction variation. The geometric environment has a small residual effect, and this effect is larger for voids than any other type of geometric environment. This could provide a test of the physics applied to cosmological-scale galaxy evolution simulations as it combines large-scale effects with local environmental impact. [ABSTRACT FROM AUTHOR]

We introduce a practical methodology for investigating the star formation and chemical evolution history of a galaxy: age-divided mean stellar populations (ADPs) from full spectrum fitting. In this method, the mass-weighted mean stellar populations and mass fractions (f mass) of young and old stellar components in a galaxy are separately estimated, which are divided with an age cut (selected to be 109.5 yr ≈3.2 Gyr in this paper). To examine the statistical reliability of ADPs, we generate 10 000 artificial galaxy spectra, each of which consists of five random simple stellar population components. Using the Penalized PiXel-Fitting (ppxf) package, we conduct full spectrum fitting to the artificial spectra with noise as a function of wavelength, imitating the real noise of Sydney-Australian Astronomical Observatory Multi-object Integral field spectrograph (SAMI) galaxies. As a result, the Δ (= output − input) of age and metallicity appears to significantly depend on not only signal-to-noise ratio (S/N), but also luminosity fractions (f lum) of young and old components. At given S/N and f lum, Δ of young components tends to be larger than Δ of old components; e.g. σ(Δ[M/H]) ∼ 0.40 versus 0.23 at S/N = 30 and f lum = 50 per cent. The age-metallicity degeneracy appears to be insignificant, but Δlog(age/yr) shows an obvious correlation with Δ f mass for young stellar components (⁠|$\mathcal {R}\sim 0.6$|⁠). The impact of dust attenuation and emission lines appears to be mostly insignificant. We discuss how this methodology can be applied to spectroscopic studies of the formation histories of galaxies, with a few examples of SAMI galaxies. [ABSTRACT FROM AUTHOR]

Feedback from an active galactic nucleus (AGN) is often implicated as a mechanism that leads to the quenching of galactic star formation. However, AGN-driven quenching is challenging to reconcile with observations that AGN hosts tend to harbour equal (or even excess) amounts of gas compared with inactive galaxies of similar stellar mass. In this paper, we investigate whether AGN feedback happens on sub-galactic (kpc) scales, an effect that might be difficult to detect with global gas measurements. Using kpc-scale measurements of molecular gas (⁠|$\Sigma _{\rm H_2}$|⁠) and stellar mass (Σ⋆) surface densities, taken from the Extragalactic Data base for Galaxy Evolution–Calar Alto Legacy Integral Field Area survey, we show that the gas fractions of central AGN regions are typically a factor of ∼ 2 lower than those in star-forming regions. Based on four galaxies with the best spaxel statistics, the difference between AGN and star-forming gas fractions is seen even within a given galaxy, indicating that AGN feedback is able to deplete the molecular gas reservoir in the central few kpc. [ABSTRACT FROM AUTHOR]

In this paper, we present an attempt to estimate the redshift evolution of the molecular to neutral gas mass ratio within galaxies (at fixed stellar mass). For a sample of five nearby grand design spirals located on the main-sequence (MS) of star-forming galaxies, we exploit maps at 500 pc resolution of stellar mass and star formation rate (M ⋆ and SFR). For the same cells, we also have estimates of the neutral (M H  i ) and molecular (⁠|$M_{\rm H_2}$|⁠) gas masses. To compute the redshift evolution, we exploit two relations: (i) one between the molecular-to-neutral mass ratio and the total gas mass (M gas), whose scatter shows a strong dependence with the distance from the spatially resolved MS, and (ii) the one between |$\log (M_{\rm {H_2}}/M_{\star })$| and log (M H  i / M ⋆). For both methods, we and that |$M_{\rm H_2}$| / M H  i within the optical radius slightly decreases with redshift, contrary to common expectations of galaxies becoming progressively more dominated by molecular hydrogen at high redshifts. We discuss possible implications of this trend on our understanding of the internal working of high-redshift galaxies. [ABSTRACT FROM AUTHOR]

The first deep-field observations of the JWST have immediately yielded a surprisingly large number of very high redshift candidates, pushing the frontier of observability well beyond z ≳ 10. We here present a detailed SED-fitting analysis of the 10 gravitationally lensed z ∼ 9–16 galaxy candidates detected behind the galaxy cluster SMACS J0723.3−7327 in a previous paper using the BEAGLE tool. Our analysis makes use of dynamical considerations to place limits on the ages of these galaxies and of all three published SL models of the cluster to account for lensing systematics. We find the majority of these galaxies to have relatively low stellar masses |$M_{\star }\sim 10^7-10^8\, \mathrm{M}_{\odot }$| and young ages t age ∼ 10–100 Myr but with a few higher mass exceptions (⁠|$M_{\star }\sim 10^9\rm{-}10^{10}\, \mathrm{M}_{\odot }$|⁠) due to Balmer-break detections at z ∼ 9–10. Because of their very blue UV-slopes, down to β ∼ −3, all of the galaxies in our sample have extremely low dust attenuations AV ≲ 0.02. Placing the measured parameters into relation, we find a very shallow M ⋆ − M UV-slope and high sSFRs above the main sequence of star formation with no significant redshift-evolution in either relation. This is in agreement with the bright UV luminosities measured for these objects and indicates that we are naturally selecting UV-bright galaxies that are undergoing intense star formation at the time they are observed. Finally, we discuss the robustness of our high-redshift galaxy sample regarding low-redshift interlopers and conclude that low-redshift solutions can safely be ruled out for roughly half of the sample, including the highest redshift galaxies at z ∼ 12–16. These objects represent compelling targets for spectroscopic follow-up observations with JWST and ALMA. [ABSTRACT FROM AUTHOR]

Galaxies display several well-behaved scaling relations between their properties, such as the star formation rate–stellar mass relation (the main sequence, MS) and the stellar mass–halo mass relation (SHMR). In principle, these scaling relations could imply different star formation histories (SFHs) of galaxies and different constraints on galaxy formation physics. In this paper, we derive the SFHs of galaxies by assuming that they always follow the SHMRs at different redshifts and use an empirical model to constrain key processes in their baryon cycle. It is found that, besides cold accretion due to halo growth, outflow of gas produced by stellar feedback has to be recycled to sustain the derived SFHs of galaxies. The recycled fraction is strongly affected by the baryon fraction in accreted low-mass haloes and the mass loading factor that quantifies the ratio between the galactic outflow rate and star formation rate. Our fiducial model predicts that around 20–60 per cent of outflow is recycled in |$\sim 0.5\!-\!4\, \mathrm{Gyr}$|⁠ , while simulations predict a slightly higher recycle fraction and a lower recycle time. We argue that strong constraints on the baryon cycle process can be obtained from future observation of the circum-galactic medium (CGM) of galaxies, such as the gas cooling rate of CGM. We also find that the implied SFHs from the SHMRs indicate that galaxies stay on the MS only for part of their lifetimes. Our model reproduces the evolution of the mass–metallicity relation as well. [ABSTRACT FROM AUTHOR]

A fundamental prediction of the ΛCDM cosmology is the hierarchical build-up of structure and therefore the successive merging of galaxies into more massive ones. As one can only observe galaxies at one specific time in the cosmic history, this merger history remains, in principle, unobservable. By using the TNG100 simulation of the IllustrisTNG project, we show that it is possible to infer the unobservable stellar assembly and merger history of central galaxies from their observable properties by using machine learning techniques. In particular, in this first paper of ERGO-ML (Extracting Reality from Galaxy Observables with Machine Learning), we choose a set of seven observable integral properties of galaxies to infer the stellar ex-situ fraction, the average merger lookback times and mass ratios, and the lookback time and stellar mass of the last major merger. To infer the posterior distribution for these parameters and hence estimate the uncertainties in the predictions, we use a conditional Invertible Neural Network (cINN). We find that the stellar ex-situ fraction and the time of the last major merger are well-determined by the selected set of observables, that the mass-weighted merger mass ratio is unconstrained, and that, beyond stellar mass, stellar morphology and stellar age are the most informative properties. Finally, we show that the cINN recovers the remaining unexplained scatter and secondary cross-correlations. Overall, this is a first step towards a tool that can be applied to large galaxy surveys in order to infer unobservable properties of the galaxies' past, enabling empirical studies of galaxy evolution enriched by cosmological simulations. [ABSTRACT FROM AUTHOR]

Satellite galaxies in the cluster environment are more likely to be quenched than galaxies in the general field. Recently, it has been reported that satellite galaxy quenching depends on the orientation relative to their central galaxies: satellites along the major axis of centrals are more likely to be quenched than those along the minor axis. In this paper, we report a detection of such anisotropic quenching up to z ∼ 1 based on a large optically selected cluster catalogue constructed from the Hyper Suprime-Cam Subaru Strategic Program. We calculate the quiescent satellite galaxy fraction as a function of orientation angle measured from the major axis of central galaxies and find that the quiescent fractions at 0.25 < z < 1 are reasonably fitted by sinusoidal functions with amplitudes of a few per cent. Anisotropy is clearer in inner regions (< r 200m) of clusters and not significant in cluster outskirts (> r 200m). We also confirm that the observed anisotropy cannot be explained by differences in local galaxy density or stellar mass distribution along the two axes. Quiescent fraction excesses between the two axes suggest that the quenching efficiency contributing to the anisotropy is almost independent of stellar mass, at least down to our stellar mass limit of |$M_{*}=1\times 10^{10}\, {\rm M}_{\odot }$|⁠. Finally, we argue that the physical origins of the observed anisotropy should have shorter quenching time-scales than |$\sim 1\, \mathrm{Gyr}$|⁠ , like ram-pressure stripping, because, for anisotropic quenching to be observed, satellites must be quenched before their initial orientation angles are significantly changed. [ABSTRACT FROM AUTHOR]

Recent years have seen growing interest in post-processing cosmological simulations with radiative transfer codes to predict observable fluxes for simulated galaxies. However, this can be slow, and requires a number of assumptions in cases where simulations do not resolve the interstellar medium (ISM). Zoom-in simulations better resolve the detailed structure of the ISM and the geometry of stars and gas; however, statistics are limited due to the computational cost of simulating even a single halo. In this paper, we make use of a set of high-resolution, cosmological zoom-in simulations of massive (⁠|$M_{\star }\gtrsim 10^{10.5}\, \rm {M_{\odot }}$| at z = 2), star-forming galaxies from the FIRE suite. We run the skirt radiative transfer code on hundreds of snapshots in the redshift range 1.5 < z < 5 and calibrate a power-law scaling relation between dust mass, star formation rate, and |$870\, \mu \rm {m}$| flux density. The derived scaling relation shows encouraging consistency with observational results from the sub-millimetre-selected AS2UDS sample. We extend this to other wavelengths, deriving scaling relations between dust mass, stellar mass, star formation rate, and redshift and sub-millimetre flux density at observed-frame wavelengths between |$\sim \! 340$| and |$\sim \! 870\, \mu \rm {m}$|⁠. We then apply the scaling relations to galaxies drawn from EAGLE, a large box cosmological simulation. We show that the scaling relations predict EAGLE sub-millimetre number counts that agree well with previous results that were derived using far more computationally expensive radiative transfer techniques. Our scaling relations can be applied to other simulations and semi-analytical or semi-empirical models to generate robust and fast predictions for sub-millimetre number counts. [ABSTRACT FROM AUTHOR]

In the framework of an ongoing project aimed at searching for and studying eXtremely Metal-Poor (XMP) very gas-rich blue dwarfs in nearby voids, we conducted spectroscopy with the 11-m Southern African Large Telescope (SALT) of 26 candidates, preselected in the first paper of this series (PEPK19). For 23 of them, we detected oxygen lines, allowing us to estimate the gas O/H ratio. For 10 of them, the oxygen abundance is found to be very low, in the range of 12 + log (O/H) = 6.95–7.30 dex. Of those, four void dwarfs have 12 + log (O/H) < 7.19, or Z < Z⊙/30. For the majority of observed galaxies, the faint line [O  iii ] λ4363 Å used to estimate O/H with the direct T e method appeared either too noisy or was not detected. We therefore use the semi-empirical method of Izotov & Thuan for these spectra, or, when applicable, the new 'Strong line' method of Izotov et al. We present and discuss the results for all void dwarfs observed in this work. We also compare their O/H values with O/H values of ∼140 void galaxies available from our recent papers. We address the properties of the newly found unusual void XMP dwarfs and compare them with those for 10 known prototype void XMP objects. The latter small group is outstanding based on their very small mass fraction of stars (only 0.01–0.02 of the baryonic mass), the blue colours of stars in the outer body indicating a non-cosmological age for the main star-forming episode), and the low gas metallicity (several times lower than expected for their luminosity). [ABSTRACT FROM AUTHOR]

We introduce serra , a suite of zoom-in high-resolution (⁠|$1.2\times 10^4 \, {\rm M}_{\odot }$|⁠ , |$\simeq 25\, {\rm {pc}}$| at z  = 7.7) cosmological simulations including non-equilibrium chemistry and on-the-fly radiative transfer. The outputs are post-processed to derive galaxy ultraviolet (UV) + far-infrared (FIR) continuum and emission line properties. Results are compared with available multiwavelength data to constrain the physical properties [e.g. star formation rates (SFRs), stellar/gas/dust mass, metallicity] of high-redshift 6 ≲ z ≲ 15 galaxies. This flagship paper focuses on the z  = 7.7 sub-sample, including 202 galaxies with stellar mass |$10^7 \, {\rm M}_{\odot }\lesssim M_\star \lesssim 5\times 10^{10}\, {\rm M}_{\odot }$|⁠ , and specific star formation rate ranging from |${\rm sSFR} \sim 100\, {\rm Gyr}^{-1}$| in young, low-mass galaxies to |$\sim 10\, {\rm Gyr}^{-1}$| for older, massive ones. At this redshift, serra galaxies are typically bursty, i.e. they are located above the Schmidt–Kennicutt relation by a factor |$\kappa _s = 3.03^{+4.9}_{-1.8}$|⁠ , consistent with recent findings for [O  iii ] and [C  ii ] emitters at high z. They also show relatively large InfraRed eXcess (IRX = L FIR/ L UV) values as a result of their compact/clumpy morphology effectively blocking the stellar UV luminosity. Note that this conclusion might be affected by insufficient spatial resolution at the molecular cloud level. We confirm that early galaxies lie on the standard [C  ii ] |$\!-\!\rm SFR$| relation; their observed L [OIII]/ L [CII] ≃ 1–10 ratios can be reproduced by a part of the serra galaxies without the need of a top-heavy initial mass function and/or anomalous C/O abundances. [O  i ] line intensities are similar to local ones, making ALMA high- z detections challenging but feasible (⁠|$\sim 6\, \rm h$| for an SFR of |$50\, \, {\rm M}_{\odot }\, {\rm yr}^{-1}$|⁠). [ABSTRACT FROM AUTHOR]

The stellar surface density within the inner 1 kpc (Σ1) has become a popular tool for understanding the growth of galaxies and its connection with the quenching of star formation. The emerging picture suggests that building a central dense core is a necessary condition for quenching. However, it is not clear whether changes in Σ1 trace changes in stellar kinematics and the growth of dispersion-dominated bulges. In this paper, we combine imaging from the Sloan Digital Sky Survey with stellar kinematics from the Sydney-AAO Multi-object Integral-field unit and Mapping Nearby Galaxies at Apache Point Observatory surveys to quantify the correlation between Σ1 and the proxy for stellar spin parameter within one effective radius (λre) for 1599 nearby galaxies. We show that, on the star-forming main sequence and at fixed stellar mass, changes in Σ1 are mirrored by changes in λre. While forming stars, main-sequence galaxies remain rotationally-dominated systems, with their Σ1 increasing but their stellar spin staying either constant or slightly increasing. The picture changes below the main sequence, where Σ1 and λre are no longer correlated. Passive systems show a narrower range of Σ1, but a wider range of λre compared to star-forming galaxies. Our results indicate that, from a structural point of view, passive galaxies are a more heterogeneous population than star-forming systems, and may have followed a variety of evolutionary paths. This also suggests that, if dispersion-dominated bulges still grow significantly at z ∼ 0, this generally takes place during, or after, the quenching phase. [ABSTRACT FROM AUTHOR]

We use the magnetic-hydrodynamical simulation TNG50 to study the evolution of barred massive disc galaxies. Massive spiral galaxies are already present as early as z  = 4, and bar formation takes place already at those early times. The bars grow longer and stronger as the host galaxies evolve, with the bar sizes increasing at a pace similar to that of the disc scalelengths. The bar fraction mildly evolves with redshift for galaxies with |$M_{*}\ge 10^{10}\rm M_{\odot }$|⁠ , being greater than |$\sim 40{{\ \rm per\ cent}}$| at 0.5 < z < 3 and |$\sim 30{{\ \rm per\ cent}}$| at z  = 0. When bars larger than a given physical size (⁠|$\ge 2\, \rm kpc$|⁠) or the angular resolution limit of twice the I -band angular PSF FWHM of the HST are considered, the bar fraction dramatically decreases with increasing redshift, reconciling the theoretical predictions with observational data. We find that barred galaxies have an older stellar population, lower gas fractions, and star formation rates than unbarred galaxies. In most cases, the discs of barred galaxies assembled earlier and faster than the discs of unbarred galaxies. We also find that barred galaxies are typical in haloes with larger concentrations and smaller spin parameters than unbarred galaxies. Furthermore, the inner regions of barred galaxies are more baryon-dominated than those of unbarred galaxies but have comparable global stellar mass fractions. Our findings suggest that the bar population could be used as a potential tracer of the buildup of disc galaxies and their host haloes. With this paper, we release a catalogue of barred galaxies in TNG50 at six redshifts between z  = 4 and 0. [ABSTRACT FROM AUTHOR]

In this paper, we investigate how massive central galaxies cease their star formation by comparing theoretical predictions from cosmological simulations: EAGLE, Illustris, and IllustrisTNG with observations of the local Universe from the Sloan Digital Sky Survey (SDSS). Our machine learning (ML) classification reveals supermassive black hole mass (M BH) as the most predictive parameter in determining whether a galaxy is star forming or quenched at redshift z  = 0 in all three simulations. This predicted consequence of active galactic nucleus (AGN) quenching is reflected in the observations, where it is true for a range of indirect estimates of M BH via proxies as well as its dynamical measurements. Our partial correlation analysis shows that other galactic parameters lose their strong association with quiescence, once their correlations with M BH are accounted for. In simulations, we demonstrate that it is the integrated power output of the AGN, rather than its instantaneous activity, which causes galaxies to quench. Finally, we analyse the change in molecular gas content of galaxies from star-forming to passive populations. We find that both gas fractions (f gas) and star formation efficiencies (SFEs) decrease upon transition to quiescence in the observations but SFE is more predictive than f gas in the ML passive/star-forming classification. These trends in the SDSS are most closely recovered in IllustrisTNG and are in direct contrast with the predictions made by Illustris. We conclude that a viable AGN feedback prescription can be achieved by a combination of preventative feedback and turbulence injection which together quench star formation in central galaxies. [ABSTRACT FROM AUTHOR]

The James Webb Space Telescope will have the power to characterize high-redshift quasars at z ≥ 6 with an unprecedented depth and spatial resolution. While the brightest quasars at such redshift (i.e. with bolometric luminosity |$L_{\rm bol}\geqslant 10^{46}\, \rm erg/s$|⁠) provide us with key information on the most extreme objects in the Universe, measuring the black hole (BH) mass and Eddington ratios of fainter quasars with |$L_{\rm bol}= 10^{45}-10^{46}\, \rm erg\,s^{ -1}$| opens a path to understand the build-up of more normal BHs at z ≥ 6. In this paper, we show that the Illustris, TNG100, TNG300, Horizon-AGN, EAGLE, and SIMBA large-scale cosmological simulations do not agree on whether BHs at z ≥ 4 are overmassive or undermassive at fixed galaxy stellar mass with respect to the M BH − M ⋆ scaling relation at z = 0 (BH mass offsets). Our conclusions are unchanged when using the local scaling relation produced by each simulation or empirical relations. We find that the BH mass offsets of the simulated faint quasar population at z ≥ 4, unlike those of bright quasars, represent the BH mass offsets of the entire BH population, for all the simulations. Thus, a population of faint quasars with |$L_{\rm bol}= 10^{45}-10^{46}\, \rm erg\,s^{ -1}$| observed by JWST can provide key constraints on the assembly of BHs at high redshift. Moreover, this will help constraining the high-redshift regime of cosmological simulations, including BH seeding, early growth, and co-evolution with the host galaxies. Our results also motivate the need for simulations of larger cosmological volumes down to z ∼ 6, with the same diversity of subgrid physics, in order to gain statistics on the most extreme objects at high redshift. [ABSTRACT FROM AUTHOR]

We present the first in a series of papers in The role of Environment in shaping Low-mass Early-type Nearby galaxies (hELENa) project. In this paper, we combine our sample of 20 low-mass early types (dEs) with 258 massive early types (ETGs) from the ATLAS3D survey - all observed with the SAURON integral field unit - to investigate early-type galaxies' stellar population scaling relations and the dependence of the population properties on local environment, extended to the low-σ regime of dEs. The ages in our sample show more scatter at lower σ values, indicative of less massive galaxies being affected by the environment to a higher degree. The shape of the age-σ relations for cluster versus non-cluster galaxies suggests that cluster environment speeds up the placing of galaxies on the red sequence. While the scaling relations are tighter for cluster than for the field/group objects, we find no evidence for a difference in average population characteristics of the two samples. We investigate the properties of our sample in the Virgo cluster as a function of number density (rather than simple clustrocentric distance) and find that dE ages correlate with the local density such that galaxies in regions of lower density are younger, likely because they are later arrivals to the cluster or have experienced less pre-processing in groups, and consequently used up their gas reservoir more recently. Overall, dE properties correlate more strongly with density than those of massive ETGs, which was expected as less massive galaxies are more susceptible to external influences. [ABSTRACT FROM AUTHOR]

The diffuse extragalactic background light (EBL) is formed by ultraviolet (UV), optical, and infrared (IR) photons mainly produced by star formation processes over the history of the Universe and contains essential information about galaxy evolution and cosmology. Here, we present a new determination of the evolving EBL spectral energy distribution using a novel approach purely based on galaxy data aiming to reduce current uncertainties on the higher redshifts and IR intensities. Our calculations use multiwavelength observations from the UV to the far-IR of a sample of approximately 150 000 galaxies detected up to z  ∼ 6 in the five fields of the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey from the Hubble Space Telescope. This is one of the most comprehensive and deepest multiwavelength galaxy data sets ever obtained. These unprecedented resources allow us to derive the overall EBL evolution up to z  ∼ 6 and its uncertainties. Our results agree with cosmic observables estimated from galaxy surveys and γ-ray attenuation such as monochromatic luminosity densities, including those in the far-IR, and star formation rate densities, also at the highest redshifts. Optical depths from our EBL approximation, which will be robust at high redshifts and for γ-rays up to tens of TeV, will be reported in a companion paper. [ABSTRACT FROM AUTHOR]

We present the KMOS Galaxy Evolution Survey (KGES), a K -band Multi-Object Spectrograph (KMOS) study of the H α and [N  ii ] emission from 288 K -band-selected galaxies at 1.2 ≲ z ≲ 1.8, with stellar masses in the range |$\log _{10}(M_{*}/\rm {M}_{\odot })\approx 9$|  – 11.5. In this paper, we describe the survey design, present the sample, and discuss the key properties of the KGES galaxies. We combine KGES with appropriately matched samples at lower redshifts from the KMOS Redshift One Spectroscopic Survey (KROSS) and the SAMI Galaxy Survey. Accounting for the effects of sample selection, data quality, and analysis techniques between surveys, we examine the kinematic characteristics and angular momentum content of star-forming galaxies at z ≈ 1.5, ≈1, and ≈0. We find that stellar mass, rather than redshift, most strongly correlates with the disc fraction amongst star-forming galaxies at z ≲ 1.5, observing only a modest increase in the prevalence of discs between z ≈ 1.5 and z ≈ 0.04 at fixed stellar mass. Furthermore, typical star-forming galaxies follow the same median relation between specific angular momentum and stellar mass, regardless of their redshift, with the normalization of the relation depending more strongly on how disc-like a galaxy's kinematics are. This suggests that massive star-forming discs form in a very similar manner across the ≈10 Gyr encompassed by our study and that the inferred link between the angular momentum of galaxies and their haloes does not change significantly across the stellar mass and redshift ranges probed in this work. [ABSTRACT FROM AUTHOR]

We report the discovery of an intrinsically faint, quintuply-imaged, dusty galaxy MACS0600-z6 at a redshift z = 6.07 viewed through the cluster MACSJ0600.1–2008 (z = 0.46). A ≃ 4σ dust detection is seen at 1.2mm as part of the ALMA Lensing Cluster Survey (ALCS), an on-going ALMA Large programme, and the redshift is secured via [C  ii ] 158 μ m emission described in a companion paper. In addition, spectroscopic follow-up with GMOS/Gemini-North shows a break in the galaxy's spectrum, consistent with the Lyman break at that redshift. We use a detailed mass model of the cluster and infer a magnification μ ≳ 30 for the most magnified image of this galaxy, which provides an unprecedented opportunity to probe the physical properties of a sub-luminous galaxy at the end of cosmic reionization. Based on the spectral energy distribution, we infer lensing-corrected stellar and dust masses of |$\rm {2.9^{+11.5}_{-2.3}\times 10^9}$| and |$\rm {4.8^{+4.5}_{-3.4}\times 10^6}$| |$\rm {M_{\odot }}$|⁠ , respectively, a star formation rate of |$\rm {9.7^{+22.0}_{-6.6} \, M_{\odot } \, yr^{-1}}$|⁠ , an intrinsic size of |$\rm {0.54^{+0.26}_{-0.14}}$| kpc, and a luminosity-weighted age of 200 ± 100 Myr. Strikingly, the dust production rate in this relatively young galaxy appears to be larger than that observed for equivalent, lower redshift sources. We discuss if this implies that early supernovae are more efficient dust producers and the consequences for using dust mass as a probe of earlier star formation. [ABSTRACT FROM AUTHOR]

We demonstrate how the total luminosity in satellite galaxies is a powerful probe of dark matter haloes around central galaxies. The method cross-correlates central galaxies in spectroscopic galaxy samples with fainter galaxies detected in photometric surveys. Using models, we show that the total galaxy luminosity, L sat, scales linearly with host halo mass, making L sat an excellent proxy for M h. L sat is also sensitive to the formation time of the halo. We demonstrate that probes of galaxy large-scale environment can break this degeneracy. Although this is an indirect probe of the halo, it yields a high signal-to-noise ratio measurement for galaxies expected to occupy haloes at <1012 M⊙, where other methods suffer from larger errors. In this paper, we focus on observational and theoretical systematics in the L sat method. We test the robustness of our method of finding central galaxies and our methods of estimating the number of background galaxies. We implement this method on galaxies in the Sloan Digital Sky Survey (SDSS) data, with satellites identified in fainter imaging data. We find excellent agreement between our theoretical predictions and the observational measurements. Finally, we compare our L sat measurements to weak lensing estimates of M h for red and blue subsamples. In the stellar mass range where the measurements overlap, we find consistent results, where red galaxies live in larger haloes. However, the L sat approach allows us to probe significantly lower mass galaxies. At these masses, the L sat values are equivalent. This example shows the potential of L sat as a probe of dark haloes. [ABSTRACT FROM AUTHOR]

This series of papers aims at understanding the formation and evolution of non-barred disc galaxies. We use the new spectro-photometric decomposition code, c2d , to separate the spectral information of bulges and discs of a statistically representative sample of galaxies from the CALIFA survey. Then, we study their stellar population properties analysing the structure-independent datacubes with the Pipe3D algorithm. We find a correlation between the bulge-to-total (B / T) luminosity (and mass) ratio and galaxy stellar mass. The B / T mass ratio has only a mild evolution with redshift, but the bulge-to-disc (B / D) mass ratio shows a clear increase of the disc component since redshift z < 1 for massive galaxies. The mass–size relation for both bulges and discs describes an upturn at high galaxy stellar masses (log (M ⋆/M⊙) > 10.5). The relation holds for bulges but not for discs when using their individual stellar masses. We find a negligible evolution of the mass–size relation for both the most massive (⁠|$\log {(M_{\star \rm ,b,d}/{\rm M}_{\odot })} \gt 10$|⁠) bulges and discs. For lower masses, discs show a larger variation than bulges. We also find a correlation between the Sérsic index of bulges and both galaxy and bulge stellar mass, which does not hold for the disc mass. Our results support an inside-out formation of nearby non-barred galaxies, and they suggest that (i) bulges formed early-on and (ii) they have not evolved much through cosmic time. However, we find that the early properties of bulges drive the future evolution of the galaxy as a whole, and particularly the properties of the discs that eventually form around them. [ABSTRACT FROM AUTHOR]

We present mock catalogues created to support the interpretation of the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS). We extract haloes along past light-cones from the Bolshoi Planck dissipationless N-body simulations and populate these haloes with galaxies using two different independently developed semi-analytic models of galaxy formation and the empirical model universemachine. Our mock catalogues have geometries that encompass the footprints of observations associated with the five CANDELS fields. In order to allow field-to-field variance to be explored, we have created eight realizations of each field. In this paper, we present comparisons with observable global galaxy properties, including counts in observed frame bands, luminosity functions, colour–magnitude distributions and colour–colour distributions. We additionally present comparisons with physical galaxy parameters derived from SED fitting for the CANDELS observations, such as stellar masses and star formation rates. We find relatively good agreement between the model predictions and CANDELS observations for luminosity and stellar mass functions. We find poorer agreement for colours and star formation rate distributions. All of the mock light-cones as well as curated 'theory friendly' versions of the observational CANDELS catalogues are made available through a web-based data hub. [ABSTRACT FROM AUTHOR]

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 samples 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. [ABSTRACT FROM AUTHOR]

There is a growing consensus that the vast majority of ultradiffuse galaxies (UDGs) are dwarf galaxies. However, there remain a few UDGs that seem to be special in terms of their globular cluster (GC) systems. In particular, according to some authors, certain UDGs exhibit large GC populations when compared to expectations from their stellar (or total) mass. Among these special UDGs, DF44 in the Coma cluster is one of the better-known examples. DF44 has been claimed to have a relatively high number of GCs, |$N_{\mathrm{ GC}}=74^{+18}_{-18}$|⁠ , for a stellar mass of only |$3\times 10^8\, \mathrm{ M}_{ \odot}$| which would indicate a much larger dark halo mass than dwarfs of similar stellar mass. In this paper, we revisit this number and, contrary to previous results, find |$N_{\mathrm{ GC}}=21^{+7}_{-9}$| assuming that the distribution of the GCs follows the same geometry as the galaxy. If we assume that the GCs around DF44 are distributed in a (projected) circularly symmetric way and, if we use a less strict criterion for the selection of the GCs, we find |$N_{\mathrm{ GC}}=18^{+23}_{-12}$|⁠. Making use of the M GC– M halo relation, this number of GCs suggests a dark matter halo mass of |$M_{\mathrm{ halo}}=1.1^{+0.4}_{-0.5} \times 10^{11} \mathrm{ M}_{\odot}$|⁠ , a value which is consistent with the expected total mass for DF44 based on its velocity dispersion, |$\sigma =33^{+3}_{-3}$| km s−1. We conclude that the number of GCs around DF44 is as expected for regular dwarf galaxies of similar stellar mass and DF44 is not extraordinary in this respect. [ABSTRACT FROM AUTHOR]

The initial sizes and masses of massive star clusters provide information about the cluster formation process and also determine how cluster populations are modified and destroyed, which have implications for using clusters as tracers of galaxy assembly. Young massive cluster populations are often assumed to be unchanged since cluster formation; therefore, their distributions of masses and radii are used as the initial values. However, the first few hundred million years of cluster evolution does change both cluster mass and cluster radius, through both internal and external processes. In this paper, we use a large suite of N -body cluster simulations in an appropriate tidal field to determine the best initial mass and initial size distributions of young clusters in the nearby galaxy M83. We find that the initial masses follow a power-law distribution with a slope of −2.7 ± 0.4 , and the half-mass radii follow a lognormal distribution with a mean of 2.57 ± 0.04 pc and a dispersion of 1.59 ± 0.01 pc. The corresponding initial projected half-light radius function has a mean of 2.7 ± 0.3 pc and a dispersion of 1.7 ± 0.2 pc. The evolution of the initial mass and size distribution functions is consistent with mass-loss and expansion due to stellar evolution, independent of the external tidal field and the cluster's initial density profile. Observed cluster sizes and masses should not be used as the initial values, even when clusters are only a few hundred million years old. [ABSTRACT FROM AUTHOR]

Using star-forming galaxies sample in the nearby Universe (0.02 < z < 0.10) selected from the Sloan Digital Sky Survey (DR7) and Galaxy Evolution Explorer all-sky survey (GR5), we present a new empirical calibration for predicting dust extinction of galaxies from the Hα-to-FUV flux ratio. We find that the Hα dust extinction (AHα) derived with Hα/Hß ratio (Balmer decrement) increases with increasing Hα/UV ratio as expected, but there remains a considerable scatter around the relation, which is largely dependent on stellar mass and/or Hα equivalent width (EWHα). At fixed Hα/UV ratio, galaxies with higher stellar mass (or galaxies with lower EWHα) tend to be more highly obscured by dust. We quantify this trend and establish an empirical calibration for predicting AHα with a combination of Hα/UV ratio, stellar mass, and EWHα, with which we can successfully reduce the systematic uncertainties accompanying the simple Hα/UV approach by ~15-30 per cent. The new recipes proposed in this study will provide a convenient tool for predicting dust extinction level of galaxies particularly when Balmer decrement is not available. By comparing AHα (derived with Balmer decrement) and AUV (derived with IR/UV luminosity ratio) for a subsample of galaxies for which AKARI far-infrared photometry is available, we demonstrate that more massive galaxies tend to have higher extra extinction towards the nebular regions compared to the stellar continuum light. Considering recent studies reporting smaller extra extinction towards nebular regions for highredshift galaxies, we argue that the dust geometry within high-redshift galaxies resembles low-mass galaxies in the nearby Universe. [ABSTRACT FROM AUTHOR]

Halo abundance matching has been used to construct a one-parameter mapping between galaxies and dark matter haloes by assuming that halo mass and galaxy luminosity (or stellar mass) are monotonically related. While this approach has been reasonably successful, it is known that galaxies must be described by at least two parameters, as can be seen from the two-parameter Fundamental Plane on which massive early-type galaxies lie. In this paper, we derive a connection between initial dark matter density perturbations in the early Universe and present-day virialized dark matter haloes by assuming simple spherical collapse combined with conservation of mass and energy. We find that z = 0 halo concentration, or alternatively the inner slope of the halo density profile α, is monotonically and positively correlated with the collapse redshift of the halo. This is qualitatively similar to the findings of some previous works based on numerical simulations, with which we compare our results. We then describe how the halo mass and concentration (or inner slope α) can be used as two halo parameters in combination with two parameters of early-type galaxies to create an improved abundance matching scheme. In a forthcoming paper, we will show an application of this scheme to galaxies on the Fundamental Plane. [ABSTRACT FROM AUTHOR]

In simple models of galaxy formation and evolution, star formation is solely regulated by the amount of gas present in the galaxy. However, it has recently been shown that star formation can be suppressed by galactic dynamics in galaxies that contain a dominant spheroidal component and a low gas fraction. This 'dynamical suppression' is hypothesized to also contribute to quenching gas-rich galaxies at high redshift, but its impact on the galaxy population at large remains unclear. In this paper, we assess the importance of dynamical suppression in the context of gas regulator models of galaxy evolution through hydrodynamic simulations of isolated galaxies, with gas-to-stellar mass ratios of 0.01–0.20 and a range of galactic gravitational potentials from disc-dominated to spheroidal. Star formation is modelled using a dynamics-dependent efficiency per free-fall time, which depends on the virial parameter of the gas. We find that dynamical suppression becomes more effective at lower gas fractions and quantify its impact on the star formation rate as a function of gas fraction and stellar spheroid mass surface density. We combine the results of our simulations with observed scaling relations that describe the change of galaxy properties across cosmic time, and determine the galaxy mass and redshift range where dynamical suppression may affect the baryon cycle. We predict that the physics of star formation can limit and regulate the baryon cycle at low redshifts (z  ≲ 1.4) and high galaxy masses (M * ≳ 3 × 1010 M⊙), where dynamical suppression can drive galaxies off the star formation main sequence. [ABSTRACT FROM AUTHOR]

We present the conditional H  i (neutral hydrogen) mass function (HIMF) conditioned on observed optical properties, M r (r -band absolute magnitude), and C ur (u − r colour), for a sample of 7709 galaxies from Arecibo Legacy Fast ALFA (40 per cent data release – α.40) which overlaps with a common volume in SDSS DR7. Based on the conditional HIMF, we find that the luminous red, luminous blue, and faint blue populations dominate the total HIMF at the high-mass end, knee, and the low-mass end, respectively. We use the conditional HIMF to derive the underlying distribution function of ΩH  i (H  i density parameter), p (ΩH  i ), in the colour–magnitude plane of galaxies. The distribution, p (ΩH  i ), peaks in the blue cloud at |$\mathit{ M_{{r}}}^{\text{max}}=-19.25, \mathit{ C_{{ur}}}^{\text{max}}=1.44$| but is skewed. It has a long tail towards faint blue galaxies, and luminous red galaxies. We argue that p (ΩH  i ) can be used to reveal the underlying relation between cold gas, stellar mass, and the star formation rate in an unbiased way, that is, the derived relation does not suffer from survey or sample selection. [ABSTRACT FROM AUTHOR]

A catalogue of galaxy clusters was obtained in an area of 414 |$\deg ^2$| up to a redshift z ∼ 0.8 from the Data Release 3 of the Kilo-Degree Survey (KiDS-DR3), using the Adaptive Matched Identifier of Clustered Objects (amico) algorithm. The catalogue and the calibration of the richness–mass relation were presented in two companion papers. Here, we describe the selection of the cluster central galaxy and the classification of blue and red cluster members, and analyse the main cluster properties, such as the red/blue fraction, cluster mass, brightness, and stellar mass of the central galaxy, and their dependence on redshift and cluster richness. We use the Illustris-TNG simulation, which represents the state-of-the-art cosmological simulation of galaxy formation, as a benchmark for the interpretation of the results. A good agreement with simulations is found at low redshifts (z ≤ 0.4), while at higher redshifts the simulations indicate a lower fraction of blue galaxies than what found in the KiDS- amico catalogue: we argue that this may be due to an underestimate of star-forming galaxies in the simulations. The selection of clusters with a larger magnitude difference between the two brightest central galaxies, which may indicate a more relaxed cluster dynamical status, improves the agreement between the observed and simulated cluster mass and stellar mass of the central galaxy. We also find that at a given cluster mass the stellar mass of blue central galaxies is lower than that of the red ones. [ABSTRACT FROM AUTHOR]

The MZ relation between stellar mass (M*) and metallicity (Z) of nearby galaxies has been described as both a global and local property, i.e. valid also on sub-galaxy scales. Here, we show that Z has remained a local property, following the gravitational potential, since z  = 3. In absorption, the MZ relation has been well studied, and was in place already at z  = 5.1. A recent absorption study of gamma-ray burst galaxies revealed a close match to damped Lyα (DLA) galaxies, surprising due to their vastly different impact parameters and leading the authors to suggest that local metallicity follows the local gravitational potential. In this paper, we formulate an observational test of this hypothesis. The test, in essence, forms a prediction that the velocity dispersion of the absorbing gas in galaxy haloes, normalized by the central velocity dispersion, must follow a steep log scale slope of −0.015 dex |$\rm kpc^{-1}$| as a function of impact parameter out to at least 20–30 kpc. We then compile an archival data and literature-based sample of galaxies seen in both emission and absorption suitable for the test, and find that current data confirm the hypothesis out to 40–60 kpc. In addition, we show that the distribution of the velocity offsets between z em and z abs favours a model where DLA systems are composed of individual sub-clouds distributed along the entire path through the halo, and disfavours a model where they are one single cloud with a bulk motion and internal sub-structure. [ABSTRACT FROM AUTHOR]

We introduce the 'Engineering Dwarfs at Galaxy Formation's Edge' (EDGE) project to study the cosmological formation and evolution of the smallest galaxies in the Universe. In this first paper, we explore the effects of resolution and sub-grid physics on a single low-mass halo (⁠|$M_{\rm halo}=10^{9}{\, \rm M}_\odot$|⁠), simulated to redshift z  = 0 at a mass and spatial resolution of |$\sim 20{\, \rm M}_\odot$| and ∼3 pc. We consider different star formation prescriptions, supernova feedback strengths, and on-the-fly radiative transfer (RT). We show that RT changes the mode of galactic self-regulation at this halo mass, suppressing star formation by causing the interstellar and circumgalactic gas to remain predominantly warm (∼104 K) even before cosmic reionization. By contrast, without RT, star formation regulation occurs only through starbursts and their associated vigorous galactic outflows. In spite of this difference, the entire simulation suite (with the exception of models without any feedback) matches observed dwarf galaxy sizes, velocity dispersions, V -band magnitudes, and dynamical mass-to-light-ratios. This is because such structural scaling relations are predominantly set by the host dark matter halo, with the remaining model-to-model variation being smaller than the observational scatter. We find that only the stellar mass–metallicity relation differentiates the galaxy formation models. Explosive feedback ejects more metals from the dwarf, leading to a lower metallicity at a fixed stellar mass. We conclude that the stellar mass–metallicity relation of the very smallest galaxies provides a unique constraint on galaxy formation physics. [ABSTRACT FROM AUTHOR]

Hydrodynamical cosmological simulations have recently made great advances in reproducing galaxy mass assembly over cosmic time – as often quantified from the comparison of their predicted stellar mass functions to observed stellar mass functions from data. In this paper, we compare the clustering of galaxies from the hydrodynamical cosmological simulated light-cone Horizon-AGN to clustering measurements from the VIDEO survey observations. Using mocks built from a VIDEO-like photometry, we first explore the bias introduced into clustering measurements by using stellar masses and redshifts derived from spectral energy distribution fitting, rather than the intrinsic values. The propagation of redshift and mass statistical and systematic uncertainties in the clustering measurements causes us to underestimate the clustering amplitude. We then find that clustering and halo occupation distribution (HOD) modelling results are qualitatively similar in Horizon-AGN and VIDEO. However, at low stellar masses, Horizon-AGN underestimates the observed clustering by up to a factor of ∼3, reflecting the known excess stellar mass to halo mass ratio for Horizon-AGN low-mass haloes, already discussed in previous works. This reinforces the need for stronger regulation of star formation in low-mass haloes in the simulation. Finally, the comparison of the stellar mass to halo mass ratio in the simulated catalogue, inferred from angular clustering, to that directly measured from the simulation validates HOD modelling of clustering as a probe of the galaxy–halo connection. [ABSTRACT FROM AUTHOR]

The star formation main sequence (SFMS) is a tight relation between the galaxy star formation rate (SFR) and its total stellar mass (M ⋆). Early-type galaxies (ETGs) are often considered as low-SFR outliers of this relation. We study, for the first time, the separated distribution in the SFR versus M ⋆ of bulges and discs of 49 ETGs from the CALIFA survey. This is achieved using c2d , a new code to perform spectrophotometric decompositions of integral field spectroscopy data cubes. Our results reflect that: (i) star formation always occurs in the disc component and not in bulges; (ii) star-forming discs in our ETGs are compatible with the SFMS defined by star-forming galaxies at z ∼ 0; (iii) the star formation is not confined to the outskirts of discs, but it is present at all radii (even where the bulge dominates the light); (iv) for a given mass, bulges exhibit lower sSFR than discs at all radii; and (v) we do not find a deficit of molecular gas in bulges with respect to discs for a given mass in our ETGs. We speculate our results favour a morphological quenching scenario for ETGs. [ABSTRACT FROM AUTHOR]

We introduce algorithms for black hole physics, i.e. black hole formation, accretion, and feedback, into the Numerical Investigation of a Hundred Astrophysical Objects (NIHAO) project of galaxy simulations. This enables us to study high mass, elliptical galaxies, where feedback from the central black hole is generally thought to have a significant effect on their evolution. We furthermore extend the NIHAO suite by 45 simulations that encompass z  = 0 halo masses from 1 × 1012 to |$4 \times 10^{13}\, \mathrm{M}_{\odot }$|⁠ , and resimulate five galaxies from the original NIHAO sample with black hole physics, which have z  = 0 halo masses from 8 × 1011 to |$3 \times 10^{12}\, \mathrm{M}_{\odot }$|⁠. Now NIHAO contains 144 different galaxies and thus has the largest sample of zoom-in simulations of galaxies, spanning z  = 0 halo masses from 9 × 108 to |$4 \times 10^{13}\, \mathrm{M}_{\odot }$|⁠. In this paper we focus on testing the algorithms and calibrating their free parameters against the stellar mass versus halo mass relation and the black hole mass versus stellar mass relation. We also investigate the scatter of these relations, which we find is a decreasing function with time and thus in agreement with observations. For our fiducial choice of parameters we successfully quench star formation in objects above a z  = 0 halo mass of |$10^{12}\, \mathrm{M}_{\odot }$|⁠ , thus transforming them into red and dead galaxies. [ABSTRACT FROM AUTHOR]

ABSTRACT Scaling relations of metallicity (O/H), star formation rate (SFR) and stellar mass ( Mstar) give important insight on galaxy evolution. They are obeyed by most galaxies in the Local Universe and also at high redshift. In a companion paper, we compiled a sample of ∼1100 galaxies from redshift 0 to ≳3, spanning almost two orders of magnitude in metal abundance, a factor of ∼106 in SFR and of ∼105 in stellar mass. We have characterized empirically the star formation 'main sequence' (SFMS) and the mass-metallicity relation (MZR) for this sample, and also identified a class of low-metallicity starbursts, rare locally but more common in the distant Universe. These galaxies deviate significantly from the main scaling relations, with high SFR and low metal content for a given Mstar. In this paper, we model the scaling relations and explain these deviations from them with a set of multi-phase chemical evolution models based on the idea that, independently of redshift, initial physical conditions in a galaxy's evolutionary history can dictate its location in the scaling relations. Our models are able to successfully reproduce the O/H, Mstar and SFR scaling relations up to z ≳ 3, and also successfully predict the molecular cloud fraction as a function of stellar mass. These results suggest that the scaling relations are defined by different modes of star formation: an 'active' starburst mode, more common at high redshift, and a quiescent 'passive' mode that is predominant locally and governs the main trends. [ABSTRACT FROM AUTHOR]