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We measure the clustering of low-redshift Sloan Digital Sky Survey (SDSS) galaxies as a function of stellar mass (⁠|$10.0\lt \log (M_*/\mathrm{M}_\odot)\lt 11.5$|⁠) and specific star formation rate (sSFR) and compare the results to models of the galaxy–halo connection. We find that the autocorrelation functions of central galaxies exhibit little dependence on sSFR, with the well-known stronger clustering of quiescent galaxies mainly attributable to satellites. Because halo assembly history is known to affect distinct halo clustering, this result implies that there is little net correlation between halo assembly history and central galaxy sSFR. However, cross-correlations with satellites are stronger for quiescent centrals than star-forming centrals, consistent with quiescent centrals having more satellites in their haloes at fixed |$M_*$|⁠ , as found in SDSS group catalogues. We model the galaxy–halo connection in an N -body simulation by assigning sSFRs to central galaxies in three different ways. Two of the models depend on halo assembly history (being based on halo accretion rate or concentration), while the third is independent of halo assembly history (being based on peak halo circular velocity, |$V_\text{peak}$|⁠ , a proxy for halo mass). All three models replicate the observed autocorrelations of central galaxies, while only the |$V_\text{peak}$| model reproduces the observed cross-correlations with satellites. This further suggests that the effects of halo assembly history may not be easily seen in autocorrelations of centrals and implies that a more complete understanding of central galaxy clustering may require more than autocorrelations of centrals alone. Additionally, the good agreement with the |$V_\text{peak}$| model supports the idea that quiescent central galaxies reside in more massive haloes than star-forming central galaxies at fixed |$M_*$|⁠. [ABSTRACT FROM AUTHOR]

We investigate the relation between galaxy structure and star formation rate (SFR) in a sample of |$\sim 2.9\times 10^{4}$| central galaxies with |$z\lt 0.0674$| and axial ratios |$b/a\gt 0.5$|⁠. The star-forming main sequence (SFMS) shows a bend around the stellar mass of |$M_\ast \le {}M_c=2\times 10^{10}{}{\rm M}_{\odot }$|⁠. At |$M_\ast \le {}M_c$|⁠ , the SFMS follows a power-law |$\text{SFR}\propto {}M_\ast ^{0.85}$|⁠ , while at higher masses it flattens. |$M_c$| corresponds to a dark matter halo mass of |$M_\text{vir}\sim {}10^{11.8}{\rm M}_{\odot }$| where virial shocks occurs. Some galaxy structure (e.g. half-light radius, |$R_e$|⁠) exhibits a non-monotonic dependence across the SFMS at a fixed |$M_\ast$|⁠. We find |$\text{SFR}\propto {R_e^{-0.28}}$| at fixed |$M_\ast$|⁠ , consistent with the global Kennicutt–Schmidt (KS) law. This finding suggests that galaxy sizes contribute to the scatter of the SFMS. However, at |$M_\ast \gt M_c$| the relationship between SFR and |$R_e$| diminishes. Low-mass galaxies above the mean of the SFMS have smaller radii, exhibit compact and centrally concentrated profiles resembling green valley (GV) and quiescent galaxies at the same mass, and have higher |$M_{\text{H}_2}{/}M_\rm{H\,{\small I}}$|⁠. Conversely, those below the SFMS exhibit larger radii, lower densities, have no GV or quiescent counterparts at their mass and have lower |$M_{\text{H}_2}/M_\rm{H\,{\small I}}$|⁠. The above data suggest two pathways for quenching low-mass galaxies, |$M_\ast \le {}M_c$|⁠ : a fast one that changes the morphology on the SFMS and a slow one that does not. Above |$M_c$|⁠ , galaxies below the SFMS resemble GV and quiescent galaxies structurally, implying that they undergo a structural transformation already within the SFMS. For these massive galaxies, CG are strongly bimodal, with SFMS galaxies exhibiting negative colour gradients, suggesting most star formation occurs in their outskirts, maintaining them within the SFMS. [ABSTRACT FROM AUTHOR]

Using spatially resolved fossil record analysis on a large sample of 'red and dead' elliptical galaxies (classical ellipticals, CLEs) from the MaNGA/SDSS-IV DR15 survey, we reconstruct the archaeological evolution of their radial gradients in mass-to-luminosity ratio (M / L), g − r colour, and specific star formation (SF) rate. We also calculate other metrics that quantify the inside-out SF quenching and external mass growth processes. The M / L gradients, ∇Υ⋆, are approximately flat at high look-back times (t lb), but then they become negative and steeper until an epoch, when this trend reverses. These trends are shifted to later epochs the less massive the galaxies are. Colour gradients follow qualitatively similar trends. We find that these trends are mainly driven by strong inside-out quenching, without significant outer growth or structural changes overall. Our results suggest a scenario where the main progenitors of local CLE galaxies evolved quasi-passively after an early dissipative phase, but underwent radial photometric changes due to the inside-out quenching that led to the systematic decrease of ∇Υ⋆ and to an increase of the light-weighted radius. The late reversing of ∇Υ⋆, t lb≈2 − 4 Gyr, roughly coincides with the global quenching of the CLE galaxies. We have pushed archaeological inferences to the limit, but thanks to the large number of objects and an understanding of how the caveats and assumptions affect our results, we conclude that they offer an average description of evolutionary behaviours of CLE progenitors that is valid at least qualitatively. [ABSTRACT FROM AUTHOR]

We investigate the formation of brightest cluster galaxies (BCGs) in the TNG300 cosmological simulation of the IllustrisTNG project. Our cluster sample consists of 700 haloes with |$M_{\rm 200}\ge 5 \times 10^{13} \, {\rm M}_{\odot }$| at z  = 0, along with their progenitors at earlier epochs. This includes 280 systems with |$M_{\rm 200}\ge 10^{14} \, {\rm M}_{\odot }$| at z  = 0, as well as three haloes with |$M_{\rm 200}\ge 10^{15} \, {\rm M}_{\odot }$|⁠. We find that the stellar masses and star formation rates of our simulated BCGs are in good agreement with observations at z ≲ 0.4, and that they have experienced, on average, ∼2 (∼3) major mergers since z  = 1 (z  = 2). Separating the BCG from the intracluster light (ICL) by means of a fixed 30 kpc aperture, we find that the fraction of stellar mass contributed by ex situ (i.e. accreted) stars at z  = 0 is approximately 70, 80, and 90 per cent for the BCG, BCG + ICL, and ICL, respectively. Tracking our simulated BCGs back in time using the merger trees, we find that they became dominated by ex situ stars at z ∼1–2, and that half of the stars that are part of the BCG at z  = 0 formed early (z ∼ 3) in other galaxies, but 'assembled' onto the BCG until later times (z ≈ 0.8 for the whole sample, z ≈ 0.5 for BCGs in |$M_{\rm 200}\ge 5 \times 10^{14} \, {\rm M}_{\odot }$| haloes). Finally, we show that the stellar mass profiles of BCGs are often dominated by ex situ stars at all radii, with stars from major mergers being found closer to the centre, while stars that were tidally stripped from other galaxies dominate the outer regions. [ABSTRACT FROM AUTHOR]

We apply stellar population synthesis analysis to obtain spatially resolved archaeological inferences for a large sample of 'red and dead' Elliptical galaxies (Classical Ellipticals, CLEs) from the MaNGA/SDSS-IV DR15 survey. From their 2D stellar light and mass maps, we explore the differences between the radial mass and light distributions in the rest-frame bands g ,  r , and i as functions of look-back time, t lb, or redshift, z. We characterize these differences through the ratios between the following mass- and light-derived global properties: sizes, concentrations, and effective surface densities. We find that the mass-to-light ratios of these properties change with t lb, more the more massive the galaxies are. The CLE galaxy archaeological progenitors are, on average, less compact, concentrated, and dense in light than in mass as z decreases. However, at later times, when also the evolution of the progenitors becomes passive at all radii, there is an upturn in these trends and the differences between mass and light in compactness/concentration decrease towards z ∼ 0. The trends in the ratios of mass-to-light sizes agree qualitatively with results from direct observations in galaxy surveys at different redshifts. We discuss the caveats and interpretations of our results, and speculate that the strong structural evolution found in some previous studies for early-type galaxies could be explained partially by photometric changes rather than by intrinsic structural changes. [ABSTRACT FROM AUTHOR]

By means of post-processed cosmological hydrodynamics simulations, we explore the ability of the fossil record method to recover the stellar mass, age gradients, and global/radial star formation and mass growth histories of galaxies observed with an optical Integral Field Unity (IFU). We use two simulations of representative Milky Way-sized galaxies, one disc-dominated and another bulge-dominated. We generate data cubes emulating MaNGA/SDSS-IV instrumental and observational conditions, and analyze them using the Pipe3D pipeline. For optimal MaNGA instrumental/observational set-ups, the global masses, ages, and dust extinctions of both galaxies are well recovered within the uncertainties, while for the radial distributions, the trend is to get slightly flatter age gradients and weaker inside-out growth modes than the true ones. The main bias is in recovering younger stellar populations in the inner, older regions, and slightly older stellar populations in the outer, younger regions, as well as lower global stellar masses. These trends are enhanced as lower is the spatial sampling/resolution (less number of fibres), more inclined and dust-attenuated is the observed galaxy, lower is the signal-to-noise ratio, and worse is the seeing. The recovered properties and histories are more affected for the disc-dominated galaxy with a prominent inside-out growth mode than for the bulge-dominated galaxy assembled earlier and more coherently. We make publicly available the code and the mock IFU datacubes used in this paper. [ABSTRACT FROM AUTHOR]

We present the results of the archaeological analysis of the stellar populations of a sample of ∼4000 galaxies observed by the SDSS-IV MaNGA survey using pipe3d. Based on this analysis we extract a sample of ∼150 000 star formation rates (SFRs) and stellar masses that mimic a single cosmological survey covering the redshift range between |$z$| ∼ 0 and |$z$| ∼ 7. We confirm that the star-forming main sequence holds as a tight relation in this range of redshifts, evolving in both the zero-point and slope. This evolution is different for local star-forming (SFGs) and retired (RGs) galaxies, with the latter presenting a stronger evolution in the zero-point and a weaker evolution in the slope. The fraction of RGs decreases rapidly with |$z$|⁠, particularly for RGs at |$z$| ∼ 0. We detect RGs well above |$z$| > 1, although not all of them are progenitors of local RGs. Finally, adopting the required corrections to make the survey complete in mass in a limited volume, we recover the cosmic SFR, stellar-mass density, and average specific SFR histories of the Universe in this wide range of look-back times. Our derivations agree with those reported by various cosmological surveys. We demonstrate that the progenitors of local RGs were more actively forming stars in the past, contributing to most of the cosmic SFR density at |$z$| > 0.5, and to most of the cosmic stellar-mass density at any redshift. They suffer a general quenching in the SFR at z ∼  0.35. Below this redshift the progenitors of local SFGs dominate the SFR density of the Universe. [ABSTRACT FROM AUTHOR]

We present a simple, efficient and robust approach to improve cosmological redshift measurements. The method is based on the presence of a reference sample for which a precise redshift number distribution (dN/dz) can be obtained for different pencil-beam-like sub-volumes within the original survey. For each sub-volume we then impose that: (i) the redshift number distribution of the uncertain redshift measurements matches the reference dN/dz corrected by their selection functions and (ii) the rank order in redshift of the original ensemble of uncertain measurements is preserved. The latter step is motivated by the fact that random variables drawn from Gaussian probability density functions (PDFs) of different means and arbitrarily large standard deviations satisfy stochastic ordering. We then repeat this simple algorithm for multiple arbitrary pencil-beam-like overlapping sub-volumes; in this manner, each uncertain measurement has multiple (non-independent) 'recovered' redshifts which can be used to estimate a new redshift PDF. We refer to this method as the Stochastic Order Redshift Technique (SORT). We have used a state-of-the-art N-body simulation to test the performance of SORT under simple assumptions and found that it can improve the quality of cosmological redshifts in a robust and efficient manner. Particularly, SORT redshifts (zsort) are able to recover the distinctive features of the so-called 'cosmic web' and can provide unbiased measurement of the two-point correlation function on scales ≳4 h-1Mpc. Given its simplicity, we envision that a method like SORT can be incorporated into more sophisticated algorithms aimed to exploit the full potential of large extragalactic photometric surveys. [ABSTRACT FROM AUTHOR]

The galaxy stellar-to-halo mass relation (SHMR) is nearly time-independent for z < 4. We therefore construct a time-independent SHMR model for central galaxies, wherein the in situ star formation rate (SFR) is determined by the halo mass accretion rate (MAR), which we call stellar halo accretion rate coevolution (SHARC). We show that the ∼0.3 dex dispersion of the halo MAR matches the observed dispersion of the SFR on the star formation main sequence (MS). In the context of 'bathtub'-type models of galaxy formation, SHARC leads to mass-dependent constraints on the relation between SFR and MAR. Despite its simplicity and the simplified treatment of mass growth from mergers, the SHARC model is likely to be a good approximation for central galaxies with M* = 109-1010.5M☉ that are on the MS, representing most of the star formation in the Universe. SHARC predictions agree with observed SFRs for galaxies on the MS at low redshifts, agree fairly well at z ∼ 4, but exceed observations at z ≳ 4. Assuming that the interstellar gas mass is constant for each galaxy (the 'equilibrium condition' in bathtub models), the SHARC model allows calculation of net mass loading factors for inflowing and outflowing gas.With assumptions about preventive feedback based on simulations, SHARC allows calculation of galaxy metallicity evolution. If galaxy SFRs indeed track halo MARs, especially at low redshifts, that may help explain the success of models linking galaxy properties to haloes (including age-matching) and the similarities between two-halo galaxy conformity and halo mass accretion conformity. [ABSTRACT FROM AUTHOR]