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The bimodality in the stellar spin of low redshift (massive) galaxies, ubiquitously existing at all star formation levels and in diverse environment, suggests that galaxies grow and quench through two diverged evolutionary pathways. For spheroid-dominated galaxies of slow stellar rotation, the age composition and metallicity of their stellar populations evidence a fast quenching history with significant gas outflows. In this work, we measure the spin parameter $\lambda_{R_{\rm e}}$, i.e. the normalized specific angular momentum of stars, out of the MaNGA integral field spectroscopy for about 10000 galaxies. Among the two thirds with HI follow-up observations ($z\lesssim0.05$), we find that, compared to fast-rotating galaxies of the same stellar mass and star formation, the galaxy population of slower rotation are generally more HI gas-poor, robust against further environmental restriction and with non-detections taken into proper account using stacking technique. This cold gas deficit of slow-rotating galaxies is most apparent at high mass $\sim10^{11}\mathcal{M}_{\odot}$ below the star formation main sequence, supporting the pivotal role of gas outflows in their quenching history. With hints from HI velocity distributions, we suspect that massive gas outflows among the slow-rotating population are facilitated by high ejective feedback efficiency, which is a result of extensive coupling between disturbed volume-filling cold gas and (commonly) biconical feedback from central black holes. By contrast, in fast-rotating disc galaxies the feedback energy mostly goes to the hot circumgalactic medium rather than directly impacts the dense and planar cold gas, thus making the feedback mainly preventive against further gas inflow., Comment: Companion of the [Universal Kinematic Bimodality] paper: see fig.6 for a concluding schematic plot

The hierarchical structure formation of our Universe inherently involves violent and chaotic episodes of mass assembly such as galaxy mergers. The level of bulk rotation of the collisionless stellar systems of galaxies reflects to what extent the galaxies, on the other hand, have assembled their stars during tranquil and ordered formation history, which fosters the growth of cohesively rotating structures. Observationally, galaxy populations show a wide spectrum of morphology and shapes, with different levels of rotational support. Despite the obvious variety and complexity, in this work we find that at a given stellar mass of galaxies, the distribution of the intrinsic spin parameter $\lambda_{R_{\rm e},\mathrm{intr}}$, i.e. the normalized specific angular momentum of stars, appears to be universally bimodal among galaxies in all star formation states and also in different environments. This ubiquitous bimodality in kinematic morphology evolves systematically with star formation and is particularly apparent for transitional galaxies of intermediate star formation rates, indicating that star formation quenching is proceeding separately within two distinct kinematic populations dominated by cold discs and hot spheroids. We show that the two populations also have contrasting recent star formation histories and metal enrichment histories, which reveal their divergent pathways to formation and quenching., Comment: Nature Astronomy in press. https://www.nature.com/articles/s41550-024-02376-8

The cold interstellar medium (ISM) as the raw material for star formation is critical to understanding galaxy evolution. It is generally understood that galaxies stop making stars when, in one way or another, they run out of gas. However, here we provide evidence that central spiral galaxies remain rich in atomic gas even if their star formation rate and molecular gas fraction have dropped significantly compared to "normal" star-forming galaxies of the same mass. Since HI is sensitive to external processes, here we investigate central spiral galaxies using a combined sample from SDSS, ALFALFA, and xGASS surveys. After proper incompleteness corrections, we find that the key HI scaling relations for central spirals show significant but regular systematic dependence on stellar mass. At any given stellar mass, the HI gas mass fraction is about constant with changing specific star formation rate (sSFR), which suggests that HI reservoir is ubiquitous in central spirals with any star formation status down to M* ~ 10^9 Msun. Together with the tight correlation between the molecular gas mass fraction and sSFR for galaxies across a wide range of different properties, it suggests that the decline of SFR of all central spirals in the local universe is due to the halt of H2 supply, though there is plenty of HI gas around. These hence provide critical observations of the dramatically different behavior of the cold multi-phase ISM, and a key to understand the star formation process and quenching mechanism., Comment: 18 pages, 7 figures; Accepted for publication in the ApJL; This is the fourth paper in the "From Haloes to Galaxies" series

In $\Lambda$CDM cosmology, galaxies form and evolve in their host dark matter (DM) halos. Halo mass is crucial for understanding the halo-galaxy connection. The abundance matching (AM) technique has been widely used to derive the halo masses of galaxy groups. However, quenching of the central galaxy can decouple the coevolution of its stellar mass and DM halo mass. Different halo assembly histories can also result in significantly different final stellar mass of the central galaxies. These processes can introduce substantial uncertainties in the halo masses derived from the AM method, particularly leading to a systematic bias between groups with star-forming centrals (blue groups) and passive centrals (red groups). To improve, we developed a new machine learning (ML) algorithm that accounts for these effects and is trained on simulations. Our results show that the ML method eliminates the systematic bias in the derived halo masses for blue and red groups and is, on average, $\sim1/3$ more accurate than the AM method. With careful calibration of observable quantities from simulations and observations from SDSS, we apply our ML model to the SDSS Yang et al. groups to derive their halo masses down to $10^{11.5}\mathrm{M_\odot}$ or even lower. The derived SDSS group halo mass function agrees well with the theoretical predictions, and the derived stellar-to-halo mass relations for both red and blue groups matches well with those obtained from direct weak lensing measurements. These new halo mass estimates enable more accurate investigation of the galaxy-halo connection and the role of the halos in galaxy evolution., Comment: 21 pages, 9 figures. Submitted to ApJ, comments welcome!

We measure the ionised gas velocity dispersions of star-forming galaxies in the MAGPI survey ($z\sim0.3$) and compare them with galaxies in the SAMI ($z\sim0.05$) and KROSS ($z\sim1$) surveys to investigate how the ionised gas velocity dispersion evolves. For the first time, we use a consistent method that forward models galaxy kinematics from $z=0$ to $z=1$. This method accounts for spatial substructure in emission line flux and beam smearing. We investigate the correlation between gas velocity dispersion and galaxy properties to understand the mechanisms that drive gas turbulence. We find that in both MAGPI and SAMI galaxies, the gas velocity dispersion more strongly correlates with the star-formation rate surface density ($\Sigma_{\rm SFR}$) than with a variety of other physical properties, and the average gas velocity dispersion is similar, at the same $\Sigma_{\rm SFR}$, for SAMI, MAGPI and KROSS galaxies. The results indicate that mechanisms related to $\Sigma_{\rm SFR}$ could be the dominant driver of gas turbulence from $z\sim1$ to $z\sim0$, for example, stellar feedback and/or gravitational instability. The gas velocity dispersion of MAGPI galaxies is also correlated with the non-rotational motion of the gas, illustrating that in addition to star-formation feedback, gas transportation and accretion may also contribute to the gas velocity dispersion for galaxies at $z\sim 0.3$. KROSS galaxies only have a moderate correlation between gas velocity dispersion and $\Sigma_{\rm SFR}$ and a higher scatter of gas velocity dispersion with respect to $\Sigma_{\rm SFR}$, in agreement with the suggestion that other mechanisms, such as gas transportation and accretion, are relatively more important at higher redshift galaxies., Comment: 15 pages, 10 figures, accepted for publication in MNRAS

It is not straightforward to physically interpret the apparent morphology of galaxies. Recent observations by James Webb Space Telescope (JWST) revealed a dominant galaxy population at high redshifts ($z>2$) that were visually classified as discs for their flattened shapes and/or exponential light profiles. The extensively accepted interpretation is that they are dynamically cold discs supported by bulk rotation. However, it is long known that flattened shapes and exponential profiles are not exclusive for rotating disc structure. To break degeneracy and assess the rotational support of typical high-$z$ galaxies in the JWST samples, those with active star formation and stellar masses $\mathrm{lg}(\mathcal{M}_{\star}/\mathcal{M}_{\odot})\sim9$, we study the kinematics of their equal-mass counterparts at $z=0$. While these local star-forming low-mass galaxies are photometrically similar to real dynamically cold discs, they are not supported by ordered rotation but primarily by random motion, and their flattened shapes result largely from tangential orbital anisotropy. Given the empirical and theoretical evidence that young galaxies are dynamically hotter at higher redshifts, our results suggest that the high-$z$ JWST galaxies may not be cold discs but are dynamically warm/hot galaxies with flattened shapes driven by anisotropy. While both having low rotational support, local low-mass galaxies possess oblate shapes, contrasting the prolate shapes (i.e. cigar-like) of low-mass systems at high redshifts. Such shape transition (prolate$\Rightarrow$oblate) indicates an associated change in orbital anisotropy (radial$\Rightarrow$tangential), with roots likely in the assembly of their host dark matter halos., Comment: 11 pages, 4 figures. ApJL accepted

The spectral energy distribution (SED) of galaxies is essential for deriving fundamental properties like stellar mass and star formation history (SFH). However, conventional methods, including both parametric and non-parametric approaches, often fail to accurately recover the observed cosmic star formation rate (SFR) density due to oversimplified or unrealistic assumptions about SFH and their inability to account for the complex SFH variations across different galaxy populations. To address this issue, we introduce a novel approach that improves galaxy broad-band SED analysis by incorporating physical priors derived from hydrodynamical simulations. Tests using IllustrisTNG simulations demonstrate that our method can reliably determine galaxy physical properties from broad-band photometry, including stellar mass within 0.05 dex, current SFR within 0.3 dex, and fractional stellar formation time within 0.2 dex, with a negligible fraction of catastrophic failures. When applied to the SDSS main photometric galaxy sample with spectroscopic redshift, our estimates of stellar mass and SFR are consistent with the widely-used MPA-JHU and GSWLC catalogs. Notably, using the derived SFHs of individual SDSS galaxies, we estimate the cosmic SFR density and stellar mass density with remarkable consistency to direct observations up to $z \sim 6$. This marks the first time SFHs derived from SEDs can accurately match observations. Consequently, our method can reliably recover observed spectral indices such as $\rm D_{\rm n}(4000)$ and $\rm H\delta_{\rm A}$ by synthesizing the full spectra of galaxies using the estimated SFHs and metal enrichment histories, relying solely on broad-band photometry as input. Furthermore, this method is extremely computationally efficient compared to conventional approaches., Comment: 22 pages, 12 figures. Submitted to ApJ, comments welcome!

The tight relationship between the stellar mass and halo mass of galaxies is one of the most fundamental scaling relations in galaxy formation and evolution. It has become a critical constraint for galaxy formation models. Over the past decade, growing evidence has convincingly shown that the stellar mass-halo mass relations (SHMRs) for star-forming and quiescent central galaxies differ significantly: at a given stellar mass, the average host halo mass of quiescent centrals is more massive than that of the star-forming centrals. Despite the importance of this feature, its scientific implications have been largely overlooked and inadequately discussed. In this work, we demonstrate that the semi-analytical model L-GALAXIES successfully reproduces these observational results, whereas three state-of-the-art hydrodynamic galaxy formation simulations (TNG, Illustris, and EAGLE) do not. Consequently, in L-GALAXIES, star-forming central galaxies are more efficient at converting baryons into stars than quiescent central galaxies at a given halo mass, while the other models predict similar efficiencies for both populations. Further analysis reveals that these fundamental discrepancies stem from distinct evolutionary paths on the stellar mass-halo mass plane. We show that the observed SHMRs for star-forming and quiescent galaxies support galaxy formation models in which quenching only weakly correlates with halo assembly histories, and in which the stellar mass of star-forming galaxies can increase significantly since cosmic noon. In contrast, models in which quenching strongly prefers to happen in early-formed halos are disfavored. Additionally, we find that galaxy downsizing is present in L-GALAXIES and TNG, but absent in Illustris and EAGLE., Comment: 12 pages, 4 figures, submitted to AAS journal, comments welcome!

We analyze the properties of a rare population, the strongly bulge-dominated early-type galaxies (referred to as sBDEs) with significant HI gas, using the databases from the FAST All Sky HI survey (FASHI) and the Arecibo Legacy Fast ALFA (ALFALFA) survey. We select the sBDEs from the Sloan Digital Sky Survey (SDSS) and cross-match with the FASHI-ALFALFA combined HI sample, resulting in 104 HI-rich sBDEs. These sBDEs tend to have extremely high HI reservoirs, which is rare in previous studies such as ATLAS$^{3D}$. 70% of the selected sBDEs are classified as quiescent galaxies, even though they have a large HI reservoir. We study the properties of these sBDEs from five main aspects: stellar population, gas-phase metallicity, stacked HI spectra, environment, and spatially resolved MaNGA data. The majority of HI-rich sBDEs appear to show lower gas-phase metallicity and are located in significantly lower-density environments, suggesting an external origin for their HI gas. We find that star-forming sBDEs exhibit statistically higher star formation efficiency and slightly older stellar populations compared to normal star-forming galaxies, suggesting a recent star formation on Gyr-timescale. They also show narrower and more concentrated HI profiles compared to control star-forming galaxies, which may explain their higher star formation efficiency., Comment: 18 pages, 14 figures, 1 table. Accepted for publication in ApJ

The gas-phase metallicity of galaxies is regulated by multiple astrophysical processes, which makes it a crucial diagnostic of galaxy formation and evolution. Beyond the fundamental mass-metallicity relation, a debate about the secondary galaxy property to predict the metallicity of galaxies arises. Motivated by this, we systematically examine the relationship between gas-phase metallicity and other galaxy properties, i.e. star formation rate (SFR) and galaxy size, in addition to stellar mass in both observation and simulation. We utilize the data from the MaNGA (Mapping Nearby Galaxies at Apache Point Observatory) survey and the TNG50 simulations. We find that the combination of $M_*/R_{\rm e}^\beta$ with $\beta\sim 0.6-1$ is in much stronger correlation to the metallicity than stellar mass alone, regardless of whether the SFR is included or not, in both observation and simulation. This indicates that galaxy size plays a more important role in determining gas-phase metallicity of galaxies than SFR. In addition, the TNG simulation predicts that the SFR, although being a subdominant role, becomes increasingly important in high-$z$ universe. Finally, we speculate that SFR modulates metallicity on the temporal dimension, synchronized with time-varying gas inflows, and galaxy size regulates metallicity on the spatial dimension by affecting the gravitational potential and the mass loading factor., Comment: 11 pages, 6 figures, ApJL accepted

The properties of the galaxies are tightly connected to their host halo mass and halo assembly history. Accurate measurement of the halo assembly history in observation is challenging but crucial to the understanding of galaxy formation and evolution. The stellar-to-halo mass ratio ($M_*/M_{\mathrm{h}}$) for the centrals has often been used to indicate the halo assembly time $t_{\mathrm{h,50}}$ of the group, where $t_{\mathrm{h,50}}$ is the lookback time at which a halo has assembled half of its present-day virial mass. Using mock data from the semi-analytic models, we find that $M_*/M_{\mathrm{h}}$ shows a significant scatter with $t_{\mathrm{h,50}}$, with a strong systematic difference between the group with a star-forming central (blue group) and passive central (red group). To improve the accuracy, we develop machine-learning models to estimate $t_{\mathrm{h,50}}$ for galaxy groups using only observable quantities in the mocks. Since star-formation quenching will decouple the co-growth of the dark matter and baryon, we train our models separately for blue and red groups. Our models have successfully recovered $t_{\mathrm{h,50}}$, within an accuracy of $\sim$ 1.09 Gyr. With careful calibrations of individual observable quantities in the mocks with SDSS observations, we apply the trained models to the SDSS Yang et al. groups and derive the $t_{\mathrm{h,50}}$ for each group for the first time. The derived SDSS $t_{\mathrm{h,50}}$ distributions are in good agreement with that in the mocks, in particular for blue groups. The derived halo assembly history, together with the halo mass, make an important step forward in studying the halo-galaxy connections in observation., Comment: 18 pages, 7 figures. Accepted by ApJ

Both simulations and observations suggest that the disk assembly of galaxies is governed by the interplay between coplanar gas inflow, ex-planar gas outflow and in-situ star formation on the disk, known as the leaky accretion disk. This scenario predicts a strong connection between radial distributions of star formation and chemical abundances. The Milky Way, being the sole galaxy where we can reliably measure star formation histories and the corresponding temporally-resolved chemical abundances with individual stars, provides a unique opportunity to scrutinize this scenario. Based on the recent large spectroscopic and photometric surveys of Milky Way stars, we obtain the radial profiles of magnesium abundance ([Mg/H]) and star formation rate (SFR) surface density at different lookback time. We find the radial profiles of [Mg/H] can be well-reproduced using the leaky accretion disk model with only two free parameters for stars formed within 4 Gyr, as well as the flattening at large radii of metallicity profiles traced by HII regions and Cepheids. Furthermore, the constraint effective yield of the Milky Way and nearby galaxies show broad consistency with the theoretical predictions from stellar chemical evolution model with a mass-loading factor of 0-2. These results support that the recent assembly of the Milky Way adheres to the leaky accretion disk scenario, bridging the disk formation of our home galaxy to the big picture of disk formation in the Universe., Comment: 11 pages, 4 figures, accepted to ApJ

We use the `Middle Ages Galaxy Properties with Integral field spectroscopy' (MAGPI) survey to investigate whether galaxies have evolved in the distribution of their stellar angular momentum in the past 3-4 Gyr, as probed by the observational proxy for spin, $\lambda_{R}$. We use 2D stellar kinematics to measure $\lambda_{R}$ along with detailed photometric models to estimate galaxy ellipticity. The combination of these measurements quantifies the kinematic classes of `fast rotators' and the rarer `slow rotators', which show no regular rotation in their line-of-sight velocity fields. We compare 51 MAGPI galaxies with $\log_{10} (M_{\star}/\mathrm{M}_\odot) > 10$ to carefully drawn samples of MaNGA galaxies in the local Universe, selected to represent possible descendants of the MAGPI progenitors. The EAGLE simulations are used to identify possible evolutionary pathways between the two samples, explicitly accounting for progenitor bias in our results and the varied evolutionary pathways a galaxy might take between the two epochs. We find that the occurrence of slow rotating galaxies is unchanged between the MAGPI ($z \sim 0.3$) and MaNGA ($z \sim 0$) samples, suggesting the massive slow rotator population was already in place $\sim 4$ Gyr ago and has not accumulated since. There is a hint of the MAGPI sample having an excess of high $\lambda_{R}$ galaxies compared to the MaNGA sample, corresponding to more ordered rotation, but statistically the samples are not significantly different. The large-scale stellar kinematics, as quantified through the $\lambda_{R}$ parameter, of galaxies at $z \sim 0.3$ have already evolved into the diversity of structures seen today in the local Universe., Comment: 10 pages, 7 figures, accepted for publication in MNRAS

Utilizing a kinematic decomposition of simulated galaxies, we focus on galaxies with tiny kinematically inferred stellar halos, indicative of weak external influences. We investigate the intricate interplay between internal (natural) and external (nurture) processes in shaping the scaling relationships of specific angular momentum ($j_\star$), stellar mass ($M_\star$), and size of disk galaxies within the IllustrisTNG simulation. The correlation among mass, size, and angular momentum of galaxies is examined by comparing simulations with observations and the theoretical predictions of the exponential hypothesis. Galaxies with tiny stellar halos exhibit a large scatter in the $j_\star$-$M_\star$ relation, which suggests that it is inherently present in their initial conditions. The analysis reveals that the disks of these galaxies adhere to the exponential hypothesis, resulting in a tight fiducial $j_\star$-$M_\star$-scale length (size) relation that is qualitatively consistent with observations. The inherent scatter in $j_\star$ provides a robust explanation for the mass-size relation and its substantial variability. Notably, galaxies that are moderately influenced by external processes closely adhere to a scaling relation akin to that of galaxies with tiny stellar halos. This result underscores the dominant role of internal processes in shaping the overall $j_\star$-$M_\star$ and mass-size relation, with external effects playing a relatively minor role in disk galaxies. Furthermore, the correlation between galaxy size and the virial radius of the dark matter halo exists but fails to provide strong evidence of the connection between galaxies and their parent dark matter halos., Comment: 11 pages, 9 figures, accepted for publication in A&A

The assembly of galaxies over cosmic time is tightly connected to the assembly of their host dark matter halos. We investigate the stellar mass growth history and the chemical enrichment history of central galaxies in SDSS-MaNGA. We find that the derived stellar metallicity of passive central galaxies is always higher than that of the star-forming ones. This stellar metallicity enhancement becomes progressively larger towards low-mass galaxies (at a given epoch) and earlier epochs (at a given stellar mass), which suggests strangulation as the primary mechanism for star formation quenching in central galaxies not only in the local universe, but also very likely at higher redshifts up to $z\sim3$. We show that at the same present-day stellar mass, passive central galaxies assembled half of their final stellar mass $\sim 2$ Gyr earlier than star-forming central galaxies, which agrees well with semi-analytic model. Exploring semi-analytic model, we find that this is because passive central galaxies reside in, on average, more massive halos with a higher halo mass increase rate across cosmic time. As a consequence, passive central galaxies are assembled faster and also quenched earlier than their star-forming counterparts. While at the same present-day halo mass, different halo assembly history also produces very different final stellar mass of the central galaxy within, and halos assembled earlier host more massive centrals with a higher quenched fraction, in particular around the "golden halo mass" at $10^{12}\mathrm{M_\odot}$. Our results call attention back to the dark matter halo as a key driver of galaxy evolution., Comment: 19 pages, 11 figures. Accepted by ApJ

We report measurements of H I content in 11 nearby, actively star-forming, blue compact dwarf galaxies (BCDs) from 21 cm observations with the Arecibo telescope. These BCDs, selected by their red (W2[4.6 $\mu$m]$-$W3[12 $\mu$m]$>$3.8 mag) and bright mid-infrared (MIR) emission (W4[22 $\mu$m]$<$ 7.6 mag), have high specific star formation rates (median sSFR $\sim$10$^{-7.8}$ yr$^{-1}$), similar to high redshift galaxies. H I emission was detected in six sources. We analyze our new detections in the context of previous H I observations of 218 dwarf irregulars (dIs) and BCDs in the literature. The $M_{\rm HI}$-$M_{\ast}$ relation resulting from our observations confirms the dominating fraction of H I gas among baryons in galaxies with lower stellar masses. This Arecibo BCD sample has significantly lower median H I depletion timescales ($\tau_{\rm HI}\sim$ 0.3 Gyr) than other dIs/BCDs ($\sim$ 6.3 Gyr) in the literature. The majority of the sources (10/11) in the Arecibo sample are very red in W1[3.4 $\mu$m]$-$W2[4.6 $\mu$m] colour ($>$ 0.8 mag) implying the presence of warm dust. We investigate the relation of $\tau_{\rm HI}$ with stellar mass ($M_{\ast}$) and sSFR. We find that $\tau_{\rm HI}$ is significantly anti-correlated with $M_{\ast}$ for higher sSFR ($>$10$^{-8.5}$ yr$^{-1}$) and with sSFR for higher stellar mass ($>10^{7.5}\,{\rm M}_{\odot}$) dwarf galaxies. The high sSFR for the BCDs in the Arecibo observed sample is mainly due to their high atomic gas star formation efficiency (SFE) or low $\tau_{\rm HI}$. The low $\tau_{\rm HI}$ or high SFE in these sources is possibly due to runaway star formation in compact and dense super star clusters., Comment: 17(12+5) pages, 7(6+1)figures, 6(4+2) tables, accepted for publication in MNRAS

We propose a novel method to quantify the assembly histories of dark matter halos with the redshift evolution of the mass-weighted spatial variance of their progenitor halos, i.e. the protohalo size history. We find that the protohalo size history for each individual halo at z~0 can be described by a double power-law function. The amplitude of the fitting function strongly correlates to the central-to-total stellar mass ratios of descendant halos. The variation of the amplitude of the protohalo size history can induce a strong halo assembly bias effect for massive halos. This effect is detectable in observation using the central-to-total stellar mass ratio as a proxy of the protohalo size. The correlation to the descendant central-to-total stellar mass ratio and the halo assembly bias effect seen in the protohalo size are much stronger than that seen in the commonly adopted half-mass formation time derived from the mass accretion history. This indicates that the information loss caused by the compression of halo merger trees to mass accretion histories can be captured by the protohalo size history. Protohalo size thus provides a useful quantity to connect protoclusters across cosmic time and to link protoclusters with their descendant clusters in observations., Comment: 20 pages, 12 + 10 figures, MNRAS accepted!

In this paper we investigate the role of AGN feedback on the late stage evolution of elliptical galaxies by performing high-resolution hydrodynamical simulation in the {\it MACER} framework. By comparing models that take into account different feedback mechanisms, namely AGN and stellar feedback, we find that AGN feedback is crucial in keeping the black hole in a low accretion state and suppressing the star formation. We then compare the energy from AGN radiation and wind deposited in the galaxy and find that only wind can compensate for the radiative cooling of the gas in the galaxy. Further, we investigate which plays the dominant role, the wind from the cold (quasar) or hot (radio) feedback modes, by examining the cumulative energy output and impact area to which the wind can heat the interstellar medium and suppress star formation. Our results indicate that first, although AGN spends most of its time in hot (radio) mode, the cumulative energy output is dominated by the outburst of the cold mode. Second, only the impact area of the cold-mode wind is large enough to heat the gas in the halo, while the hot-mode wind is not. Additionally, the cold-mode wind is capable of sweeping up the material from stellar mass loss. These results indicate the dominant role of cold-mode wind. The limitations of our model, including the absence of jet feedback, are discussed., Comment: 15 pages, 14 figures. Accepted for publication in MNRAS

We investigate the impact of environment on the internal mass distribution of galaxies using the Middle Ages Galaxy Properties with Integral field spectroscopy (MAGPI) survey. We use 2D resolved stellar kinematics to construct Jeans dynamical models for galaxies at mean redshift $z \sim 0.3$, corresponding to a lookback time of $3-4$ Gyr. The internal mass distribution for each galaxy is parameterised by the combined mass density slope $\gamma$ (baryons $+$ dark matter), which is the logarithmic change of density with radius. We use a MAGPI sample of 28 galaxies from low-to-mid density environments and compare to density slopes derived from galaxies in the high density Frontier Fields clusters in the redshift range $0.29

We investigate the two-halo galactic conformity effect for central galaxies, which is the spatial correlation of the star formation activities for central galaxies to several Mpcs, by studying the dependence of the star formation activities of central galaxies on their large-scale structure in our local Universe using the SDSS data. Here we adopt a novel environment metric using only central galaxies quantified by the distance to the $n$-th nearest central galaxy. This metric measures the environment within an aperture from $\sim$ 1 Mpc to $\gtrsim$ 10 Mpc, with a median value of $\sim$ 4 Mpc. We found that two kinds of conformity effects in our local Universe. The first one is that low-mass central galaxies are more quenched in high-density regions, and we found that this effect mainly comes from low-mass centrals that are close to a more massive halo. A similar trend is also found in the IllustrisTNG simulation, which can be entirely explained by backsplash galaxies. The second conformity effect is that massive central galaxies in low-density regions are more star-forming. This population of galaxies also possesses a higher fraction of spiral morphology and lower central stellar velocity dispersion, suggesting that their low quiescent fraction is due to less-frequent major merger events experienced in the low-density regions, and as a consequence, less-massive bulges and central black holes., Comment: 13 pages, 9 figures, MNRAS 523 1268

The cosmological inflow of a galaxy is speculated to be able to enter the galaxy and enhance the star formation rate (SFR) and black hole accretion rate (BHAR). In this paper, by performing high-resolution hydrodynamic simulations in the framework of {\it MACER}, we investigate the fate of the inflow and its impacts on the evolution of a massive elliptical galaxy. The inflow properties are adopted from the cosmological simulation IllustrisTNG. We find that, the inflow gas hardly enters but is blocked beyond $\sim 20$ kpc from the central galaxy and becomes part of the circumgalactic medium (CGM). The gas pressure gradient, mainly contributed by the thermalized stellar wind and subdominantly by the energy input from the AGN, balances gravity and prevents the inflow from entering the galaxy. The SFR and BHAR are almost not affected by the normal inflow. However, if the rate of cosmological inflow were increased by a factor of 3, a small fraction of the inflow would enter the galaxy and contribute about 10\% of the gas in the galaxy. In this case, the gas density in the galaxy would increase by a factor of $\ga$ 20. This increase is not because of the additional gas supply by the inflow but the increase of gas density in the CGM caused by the inflow. Consequently, the SFR and BHAR would increase by a factor of $\sim$ 5 and $\sim 1000$ respectively. Finally, AGN feedback can perturb the motion of the inflow and heat the CGM through its intermittent outbursts., Comment: 19 pages,13 figures, accepted for publication in MNRAS

The eighteenth data release of the Sloan Digital Sky Surveys (SDSS) is the first one for SDSS-V, the fifth generation of the survey. SDSS-V comprises three primary scientific programs, or "Mappers": Milky Way Mapper (MWM), Black Hole Mapper (BHM), and Local Volume Mapper (LVM). This data release contains extensive targeting information for the two multi-object spectroscopy programs (MWM and BHM), including input catalogs and selection functions for their numerous scientific objectives. We describe the production of the targeting databases and their calibration- and scientifically-focused components. DR18 also includes ~25,000 new SDSS spectra and supplemental information for X-ray sources identified by eROSITA in its eFEDS field. We present updates to some of the SDSS software pipelines and preview changes anticipated for DR19. We also describe three value-added catalogs (VACs) based on SDSS-IV data that have been published since DR17, and one VAC based on the SDSS-V data in the eFEDS field., Comment: Accepted to ApJS

We investigate the presence of ionised gas outflows in a sample of 141 main-sequence star-forming galaxies at $1.2 10.8$, AGN-dominated galaxies, suggesting that AGNs may be the primary drivers of these gas flows. Surprisingly, at $\log(M_\star/M_{\odot})\leq 9.6$, the observed line profiles are fully consistent with a rotating disc model, indicating that ionised gas outflows in dwarf galaxies might play a negligible role even during the peak of cosmic star-formation activity. Finally, we find that the observed mass loading factor scales with stellar mass as expected from the TNG50 cosmological simulation, but the ionised gas mass accounts for only 2$\%$ of the predicted value. This suggests that either the bulk of the outflowing mass is in other gaseous phases or the current feedback models implemented in cosmological simulations need to be revised., Comment: Accepted for publication in MNRAS, 28 pages, 20 figures

Black hole feedback has been widely implemented as the key recipe to quench star formation in massive galaxies in modern semi-analytic models and hydrodynamical simulations. As the theoretical details surrounding the accretion and feedback of black holes continue to be refined, various feedback models have been implemented across simulations, with notable differences in their outcomes. Yet, most of these simulations have successfully reproduced some observations, such as stellar mass function and star formation rate density in the local Universe. We use the recent observation on the change of neutral hydrogen gas mass (including both ${\rm H_2}$ and ${\rm HI}$) with star formation rate of massive central disc galaxies as a critical constraint of black hole feedback models across several simulations. We find that the predictions of IllustrisTNG agree with the observations much better than the other models tested in this work. This favors IllustrisTNG's treatment of active galactic nuclei - where kinetic winds are driven by black holes at low accretion rates - as more plausible amongst those we test. In turn, this also indirectly supports the idea that the massive central disc galaxy population in the local Universe was likely quenched by AGN feedback., Comment: 15 pages, 3+4 figures, accepted for publication in ApJ

While the slope of the dust attenuation curve ($\delta$) is found to correlate with effective dust attenuation ($A_V$) as obtained through spectral energy distribution (SED) fitting, it remains unknown how the fitting degeneracies shape this relation. We examine the degeneracy effects by fitting SEDs of a sample of local star-forming galaxies (SFGs) selected from the Galaxy And Mass Assembly survey, in conjunction with mock galaxy SEDs of known attenuation parameters. A well-designed declining starburst star formation history is adopted to generate model SED templates with intrinsic UV slope ($\beta_0$) spanning over a reasonably wide range. The best-fitting $\beta_0$ for our sample SFGs shows a wide coverage, dramatically differing from the limited range of $\beta_0<-2.2$ for a starburst of constant star formation. Our results show that strong degeneracies between $\beta_0$, $\delta$, and $A_V$ in the SED fitting induce systematic biases leading to a false $A_V$--$\delta$ correlation. Our simulation tests reveal that this relationship can be well reproduced even when a flat $A_V$--$\delta$ relation is taken to build the input model galaxy SEDs. The variations in best-fitting $\delta$ are dominated by the fitting errors. We show that assuming a starburst with constant star formation in SED fitting will result in a steeper attenuation curve, smaller degeneracy errors, and a stronger $A_V$--$\delta$ relation. Our findings confirm that the $A_V$--$\delta$ relation obtained through SED fitting is likely driven by the systematic biases induced by the fitting degeneracies between $\beta_0$, $\delta$, and $A_V$., Comment: 21 pages, 13 figures, accepted for publication in the MNRAS, Comments welcome!

We study the structural and environmental dependence of the star formation on the plane of stellar mass versus central core density ($\Sigma_{\rm 1\ kpc}$) in the nearby universe. We study the central galaxies in the sparse environment and find a characteristic population-averaged $\rm \Sigma_{1\ kpc} \sim 10^9-10^{9.2}\ M_{\odot}\ kpc^{-2}$, above which quenching is operating. This $\rm \Sigma^{crit}_{1\ kpc}$ only weakly depends on the stellar mass, suggesting that the mass-quenching of the central galaxies is more closely related to the processes that operate in the central regions than over the entire galaxies. For satellites, at a given stellar mass, environment-quenching appears to operate in a similar fashion as mass-quenching in centrals, also starting from galaxies with high $\rm \Sigma_{1\ kpc}$ to low $\rm \Sigma_{1\ kpc}$, and $\rm \Sigma^{crit}_{1\ kpc}$ becomes strongly mass-dependent, in particular in dense regions. This is because (1) more low-mass satellites are quenched by the environmental effects in denser regions and (2) at fixed stellar mass and environment, the environment-quenched satellites have, on average, larger $\Sigma_{\rm 1\ kpc}$, $\rm M_{1\ kpc}/M_{\star}$ and Sersic index $n$, and as well as smaller size. These results imply that either some dynamical processes change the structure of the satellites during quenching or the satellites with higher $\Sigma_{\rm 1\ kpc}$ are more susceptible to the environmental effects., Comment: 14 pages, 7 figures, accepted for publication in ApJL

We propose a random forest (RF) machine learning approach to determine the accreted stellar mass fractions ($f_\mathrm{acc}$) of central galaxies, based on various dark matter halo and galaxy features. The RF is trained and tested using 2,710 galaxies with stellar mass $\log_{10}M_\ast/M_\odot>10.16$ from the TNG100 simulation. Galaxy size is the most important individual feature when calculated in 3-dimensions, which becomes less important after accounting for observational effects. For smaller galaxies, the rankings for features related to merger histories increase. When an entire set of halo and galaxy features are used, the prediction is almost unbiased, with root-mean-square error (RMSE) of $\sim$0.068. A combination of up to three features with different types (galaxy size, merger history and morphology) already saturates the power of prediction. If using observable features, the RMSE increases to $\sim$0.104, and a combined usage of stellar mass, galaxy size plus galaxy concentration achieves similar predictions. Lastly, when using galaxy density, velocity and velocity dispersion profiles as features, which approximately represent the maximum amount of information extracted from galaxy images and velocity maps, the prediction is not improved much. Hence the limiting precision of predicting $f_\mathrm{acc}$ is $\sim$0.1 with observables, and the multi-component decomposition of galaxy images should have similar or larger uncertainties. If the central black hole mass and the spin parameter of galaxies can be accurately measured in future observations, the RMSE is promising to be further decreased by $\sim$20%., Comment: accepted by MNRAS

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 ($M_{\rm BH}$) 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 $M_{\rm BH}$ 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 $M_{\rm BH}$ 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 ($f_{\rm gas}$) and star formation efficiencies (SFEs) decrease upon transition to quiescence in the observations but SFE is more predictive than $f_{\rm gas}$ 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., Comment: 29 pages, 16 figures, accepted for publication in MNRAS

We present a comparison of the nitrogen-to-oxygen ratio (N/O) in 37 high-redshift galaxies at $z\sim$2 taken from the KMOS Lensed Emission Lines and VElocity Review (KLEVER) Survey with a comparison sample of local galaxies, taken from the Sloan Digital Sky Survey (SDSS). The KLEVER sample shows only a mild enrichment in N/O of $+$0.1 dex when compared to local galaxies at a given gas-phase metallicity (O/H), but shows a depletion in N/O of $-$0.36 dex when compared at a fixed stellar mass (M$_*$). We find a strong anti-correlation in local galaxies between N/O and SFR in the M$_*$-N/O plane, similar to the anti-correlation between O/H and SFR found in the mass-metallicity relation (MZR). We use this anti-correlation to construct a fundamental nitrogen relation (FNR), analogous to the fundamental metallicity relation (FMR). We find that KLEVER galaxies are consistent with both the FMR and the FNR. This suggests that the depletion of N/O in high-$z$ galaxies when considered at a fixed M$_*$ is driven by the redshift-evolution of the mass-metallicity relation in combination with a near redshift-invariant N/O-O/H relation. Furthermore, the existence of an fundamental nitrogen relation suggests that the mechanisms governing the fundamental metallicity relation must be probed by not only O/H, but also N/O, suggesting pure-pristine gas inflows are not the primary driver of the FMR, and other properties such as variations in galaxy age and star formation efficiency must be important., Comment: 23 pages, 11 figures, Accepted for publication in Monthly Notices of the Royal Astronomical Society

Observing nearby galaxies with submillimeter telescopes on the ground has two major challenges. First, the brightness is significantly reduced at long submillimeter wavelengths compared to the brightness at the peak of the dust emission. Second, it is necessary to use a high-pass spatial filter to remove atmospheric noise on large angular scales, which has the unwelcome by-product of also removing the galaxy's large-scale structure. We have developed a technique for producing high-resolution submillimeter images of galaxies of large angular size by using the telescope on the ground to determine the small-scale structure (the large Fourier components) and a space telescope (Herschel or Planck) to determine the large-scale structure (the small Fourier components). Using this technique, we are carrying out the HARP and SCUBA-2 High Resolution Terahertz Andromeda Galaxy Survey (HASHTAG), an international Large Program on the James Clerk Maxwell Telescope, with one aim being to produce the first high-fidelity high-resolution submillimeter images of Andromeda. In this paper, we describe the survey, the method we have developed for combining the space-based and ground-based data, and present the first HASHTAG images of Andromeda at 450 and 850um. We also have created a method to predict the CO(J=3-2) line flux across M31, which contaminates the 850um band. We find that while normally the contamination is below our sensitivity limit, the contamination can be significant (up to 28%) in a few of the brightest regions of the 10 kpc ring. We therefore also provide images with the predicted line emission removed., Comment: 26 pages, 19 figures. Submitted to ApJS June 2021, Accepted September 2021

We measure the relationship between stellar mass and stellar metallicity, the stellar mass--metallicity relation (MZR), for 1336 star-forming galaxies at $1.6\le z\le3.0$ (=2.2) using rest-frame far-ultraviolet spectra from the zCOSMOS-deep survey. High signal-to-noise composite spectra containing stellar absorption features are fit with population synthesis model spectra of a range of metallicity. We find stellar metallicities, which mostly reflect iron abundances, scaling as $(Z_{Fe,\ast}/Z_{Fe,\odot})=-(0.81\pm0.01)+(0.32+0.03)\log(M_\ast/10^{10}M_\odot)$ across the mass range of $10^9\lesssim M_\ast/M_\odot\lesssim10^{11}$, being $\approx6\times$ lower than seen locally at the same masses. The instantaneous oxygen-to-iron ratio ($\alpha$-enhancement) inferred using the gas-phase oxygen MZRs, is on average found to be [O/Fe]$\approx0.47$, being higher than the local [O/Fe]$\approx0$. The observed changes in [O/Fe] and [Fe/H] are reproduced in simple flow-through gas-regulator models with steady star-formation histories (SFHs) that follow the evolving main sequence. Our models show that the [O/Fe] is determined almost entirely by the instantaneous specific star formation rate alone while being independent of the SFHs, mass, and the gas-regulation characteristics of the systems. We find that the locations of $\sim10^{10}M_\odot$ galaxies at z~2 in the [O/Fe]--metallicity planes are in remarkable agreement with the sequence of low-metallicity thick-disk stars in our Galaxy. This manifests a beautiful concordance between the results of Galactic archaeology and observations of high-redshift Milky Way progenitors. However, there remains a question of how and when the old metal-rich, low-$\alpha$/Fe stars seen in the bulge had formed by z~2 because such a stellar population is not seen in our data and difficult to explain in the context of our models., Comment: Submitted to ApJ; 30 pages, 20 figures

In Dou et al. (2021), we introduced the Fundamental Formation Relation (FFR), a tight relation between specific SFR (sSFR), H$_2$ star formation efficiency (SFE$_{\rm H_2}$), and the ratio of H$_2$ to stellar mass. Here we show that atomic gas HI does not follow a similar FFR as H$_2$. The relation between SFE$_{\rm HI}$ and sSFR shows significant scatter and strong systematic dependence on all of the key galaxy properties that we have explored. The dramatic difference between HI and H$_2$ indicates that different processes (e.g., quenching by different mechanisms) may have very different effects on the HI in different galaxies and hence produce different SFE$_{\rm HI}$-sSFR relations, while the SFE$_{\rm H_2}$-sSFR relation remains unaffected. The facts that SFE$_{\rm H_2}$-sSFR relation is independent of other key galaxy properties, and that sSFR is directly related to the cosmic time and acts as the cosmic clock, make it natural and very simple to study how different galaxy populations (with different properties and undergoing different processes) evolve on the same SFE$_{\rm H_2}$-sSFR $\sim t$ relation. In the gas regulator model (GRM), the evolution of a galaxy on the SFE$_{\rm H_2}$-sSFR($t$) relation is uniquely set by a single mass-loading parameter $\lambda_{\rm net,H_2}$. This simplicity allows us to accurately derive the H$_2$ supply and removal rates of the local galaxy populations with different stellar masses, from star-forming galaxies to the galaxies in the process of being quenched. This combination of FFR and GRM, together with the stellar metallicity requirement, provide a new powerful tool to study galaxy formation and evolution., Comment: 16 pages, 7 figures, accepted for publication in ApJ

The phenomenological study of evolving galaxy populations has shown that star forming galaxies can be quenched by two distinct processes: mass quenching and environment quenching (Peng et al. 2010). To explore the mass quenching process in local galaxies, we study the massive central disk galaxies with stellar mass above the Schechter characteristic mass. In Zhang et al. (2019), we showed that during the quenching of the massive central disk galaxies as their star formation rate (SFR) decreases, their molecular gas mass and star formation efficiency drop rapidly, but their HI gas mass remains surprisingly constant. To identify the underlying physical mechanisms, in this work we analyze the change during quenching of various structure parameters, bar frequency, and active galactic nucleus (AGN) activity. We find three closely related facts. On average, as SFR decreases in these galaxies: (1) they become progressively more compact, indicated by their significantly increasing concentration index, bulge-to-total mass ratio, and central velocity dispersion, which are mainly driven by the growth and compaction of their bulge component; (2) the frequency of barred galaxies increases dramatically, and at a given concentration index the barred galaxies have a significantly higher quiescent fraction than unbarred galaxies, implying that the galactic bar may play an important role in mass quenching; and (3) the "AGN" frequency increases dramatically from 10% on the main sequence to almost 100% for the most quiescent galaxies, which is mainly driven by the sharp increase of LINERs. These observational results lead to a self-consistent picture of how mass quenching operates., Comment: 20 pages, 11 figures. Published in ApJ

In the $(\lambda_{\rm R}, \varepsilon)$ and $(V/\sigma, \varepsilon)$ diagrams for characterizing dynamical states, the fast-rotator galaxies (both early-type and spirals) are distributed within a well-defined leaf-shaped envelope. This was explained as due to an upper limit to the orbital anisotropy increasing with galaxy intrinsic flattening. However, a physical explanation for this empirical trend was missing. Here we construct Jeans Anisotropic Models (JAM), with either cylindrically or spherically aligned velocity ellipsoid (two extreme assumptions), and each with either spatially-constant or -variable anisotropy. We use JAM to build mock samples of axisymmetric galaxies, assuming on average an oblate shape for the velocity ellipsoid (as required to reproduce the rotation of real galaxies), and limiting the radial anisotropy $\beta$ to the range allowed by physical solutions. We find that all four mock samples naturally predict the observed galaxy distribution on the $(\lambda_{\rm R}, \varepsilon)$ and $(V/\sigma, \varepsilon)$ diagrams, without further assumptions. Given the similarity of the results from quite different models, we conclude that the empirical anisotropy upper limit in real galaxies, and the corresponding observed distributions in the $(\lambda_{\rm R}, \varepsilon)$ and $(V/\sigma, \varepsilon)$ diagrams, are due to the lack of physical axisymmetric equilibrium solutions at high $\beta$ anisotropy when the velocity ellipsoid is close to oblate., Comment: 5 pages, 4 figures, accepted for publication on MNRAS Letters

Star formation and quenching are two of the most important processes in galaxy formation and evolution. We explore in the local Universe the interrelationships among key integrated galaxy properties, including stellar mass $M_*$, star formation rate (SFR), specific SFR (sSFR), molecular gas mass $M_{\rm H_2}$, star formation efficiency (SFE) of the molecular gas and molecular gas to stellar mass ratio $\mu$. We aim to identify the most fundamental scaling relations among these key galaxy properties and their interrelationships. We show the integrated $M_{\rm H_2}$-SFR, SFR-$M_*$ and $M_{\rm H_2}$-$M_*$ relation can be simply transformed from the $\mu$-sSFR, SFE-$\mu$ and SFE-sSFR relation, respectively. The transformation, in principle, can increase or decrease the scatter of each relation. Interestingly, we find the latter three relations all have significantly smaller scatter than the former three corresponding relations. We show the probability to achieve the observed small scatter by accident is extremely close to zero. This suggests that the smaller scatters of the latter three relations are driven by a more fundamental physical connection among these quantities. We then show the large scatters in the former relations are due to their systematic dependence on other galaxy properties, and on star formation and quenching process. We propose the sSFR-$\mu$-SFE relation as the Fundamental Formation Relation (FFR), which governs the star formation and quenching process, and provides a simple framework to study galaxy evolution. Other scaling relations, including integrated Kennicutt-Schmidt law, star-forming main sequence and molecular gas main sequence, can all be derived from the FFR., Comment: This is the revised version accepted for publication in ApJ

We provide a coherent, uniform measurement of the evolution of the logarithmic star formation rate (SFR) - stellar mass ($M_*$) relation, called the main sequence of star-forming galaxies (MS), for galaxies out to $z\sim5$. We measure the MS using mean stacks of 3 GHz radio continuum images to derive average SFRs for $\sim$200,000 mass-selected galaxies at $z>0.3$ in the COSMOS field. We describe the MS relation adopting a new model that incorporates a linear relation at low stellar mass (log($M_*$/M$_\odot$)$<$10) and a flattening at high stellar mass that becomes more prominent at low redshift ($z<1.5$). We find that the SFR density peaks at $1.5

We investigate the environmental dependence of the stellar populations of galaxies in SDSS DR7. Echoing earlier works, we find that satellites are both more metal-rich (<0.1 dex) and older (<2 Gyr) than centrals of the same stellar mass. However, after separating star-forming, green valley and passive galaxies, we find that the true environmental dependence of both stellar metallicity (<0.03 dex) and age (<0.5 Gyr) is in fact much weaker. We show that the strong environmental effects found when galaxies are not differentiated result from a combination of selection effects brought about by the environmental dependence of the quenched fraction of galaxies, and thus we strongly advocate for the separation of star-forming, green valley and passive galaxies when the environmental dependence of galaxy properties are investigated. We also study further environmental trends separately for both central and satellite galaxies. We find that star-forming galaxies show no environmental effects, neither for centrals nor for satellites. In contrast, the stellar metallicities of passive and green valley satellites increase weakly (< 0.05 dex and < 0.08 dex, respectively) with increasing halo mass, increasing local overdensity and decreasing projected distance from their central; this effect is interpreted in terms of moderate environmental starvation (`strangulation') contributing to the quenching of satellite galaxies. Finally, we find a unique feature in the stellar mass--stellar metallicity relation for passive centrals, where galaxies in more massive haloes have larger stellar mass (~0.1 dex) at constant stellar metallicity; this effect is interpreted in terms of dry merging of passive central galaxies and/or progenitor bias., Comment: 22 pages, 18 figures, accepted for publication in MNRAS

We study the link between the kinematic-morphology of galaxies, as inferred from integral-field stellar kinematics, and their relation between mass and star formation rate (SFR). Our sample consists of $\sim 3200$ galaxies with integral-field spectroscopic data from the MaNGA survey with available determinations of their effective stellar angular momentum within the half-light radius $\lambda_{R_e}$. We find that for star-forming galaxies, namely along the star formation main sequence (SFMS), the $\lambda_{R_e}$ values remain large and almost unchanged over about two orders of magnitude in stellar mass, with the exception of the lowest masses $\mathcal{M}_{\star}\lesssim2\times10^{9} \mathcal{M}_{\odot}$, where $\lambda_{R_e}$ slightly decreases. The SFMS is dominated by spiral galaxies with small bulges. Below the SFMS, but above the characteristic stellar mass $\mathcal{M}_{\rm crit}\approx2\times10^{11} \mathcal{M}_{\odot}$, there is a sharp decrease in $\lambda_{R_e}$ with decreasing star formation rate: massive galaxies well below the SFMS are mainly slow-rotator early-type galaxies, namely genuinely spheroidal galaxies without disks. Below the SFMS and below $\mathcal{M}_{\rm crit}$ the decrease of $\lambda_{R_e}$ with decreasing SFR becomes modest or nearly absent: low-mass galaxies well below the SFMS, are fast-rotator early-type galaxies, and contain fast-rotating stellar disks like their star-forming counterparts. We also find a small but clear environmental dependence for the massive galaxies: in the mass range $10^{10.9}-10^{11.5} \mathcal{M}_{\odot}$, galaxies in rich groups or denser regions or classified as central galaxies have lower values of $\lambda_{R_e}$. While no environmental dependence is found for galaxies of lower mass. We discuss how our results can be understood as due to the different star formation and mass assembly histories of galaxies with varying mass., Comment: 22 pages, 12 figures, LaTeX. Accepted for publication on MNRAS

We present a detailed analysis of a large sample of spectroscopically confirmed ultra-massive quiescent galaxies (${\rm{log}}(M_{\ast}/M_{\odot})\sim11.5$) at $z\gtrsim2$. This sample comprises 15 galaxies selected in the COSMOS and UDS fields by their bright K-band magnitudes and followed up with VLT/X-shooter spectroscopy and HST/WFC3 $H_{F160W}$ imaging. These observations allow us to unambiguously confirm their redshifts ascertain their quiescent nature and stellar ages, and to reliably assess their internal kinematics and effective radii. We find that these galaxies are compact, consistent with the high mass end of the mass-size relation for quiescent galaxies at $z=2$. Moreover, the distribution of the measured stellar velocity dispersions of the sample is consistent with the most massive local early-type galaxies from the MASSIVE Survey showing that evolution in these galaxies, is dominated by changes in size. The HST images reveal, as surprisingly high, that $40\ \%$ of the sample have tidal features suggestive of mergers and companions in close proximity, including three galaxies experiencing ongoing major mergers. The absence of velocity dispersion evolution from $z=2$ to $0$, coupled with a doubling of the stellar mass, with a factor of four size increase and the observed disturbed stellar morphologies support dry minor mergers as the primary drivers of the evolution of the massive quiescent galaxies over the last 10 billion years., Comment: 30 pages, 10 figures, accepted in ApJ

In order to investigate the importance of different proposed quenching mechanisms, we use an indirect method to estimate gas masses for ~62,000 SDSS DR7 galaxies. We infer gas surface densities from dust column densities as traced by extinction within the fibre, applying a metallicity correction to account for varying dust-to-gas ratios. We find that both gas fraction and star formation efficiency (SFE) decrease moving away from the star forming main sequence (MS) towards quiescence for all galaxy masses. We further show that both quantities correlate similarly strongly with the departure from the MS, implying the need for any physical model of quenching to invoke a change in $\textit{both}$ gas fraction and SFE. Our results call for a better understanding of the physical processes driving the decrease in star formation efficiency, which has received relatively little attention in the theory of quenching until now., Comment: 7 pages, 4 figures, Accepted for publication in MNRAS Letters. In order to ensure reproducibility, all analysis is available at https://hub.docker.com/u/jpiotrowska

We present near-infrared observations of 42 gravitationally lensed galaxies obtained in the framework of the KMOS Lensed Emission Lines and VElocity Review (KLEVER) Survey, a program aimed at investigating the spatially resolved properties of the ionised gas in 1.2 3$\sigma$) "inverted" gradients are also found, showing an anti-correlation between metallicity and star formation rate density on local scales, possibly suggesting recent episodes of pristine gas accretion or strong radial flows in place. Nevertheless, the individual metallicity maps are characterised by a variety of different morphologies, with flat radial gradients sometimes hiding non-axisymmetric variations on kpc scales which are washed out by azimuthal averages, especially in interacting systems or in those undergoing local episodes of recent star formation., Comment: Main text: 23 pages, 11 figures. Appendix: 12 pages, 11 figures. Accepted for publication on MNRAS

We combine the published stellar mass function (SMF) and gas scaling relations to explore the baryonic (stellar plus cold gas) mass function (BMF) of galaxies to redshift $z=3$. We find evidence that at log$(M_{\rm baryon}/M_{\bigodot})>11.3$, the BMF evolves little since $z\sim 2.2$. With the evolution of BMF and SMF, we investigate the baryon net accretion rate ($\dot{\rho}_{\rm baryon}$) and stellar mass growth rate ($\dot{\rho}_{\rm star}$) for the galaxy population of log($M_{\rm star}/M_{\bigodot}$)>10. The ratio between these two quanties, $\dot{\rho}_{\rm baryon}$/$\dot{\rho}_{\rm star}$, decreases from $\dot{\rho}_{\rm baryon}$/$\dot{\rho}_{\rm star}\sim$2 at $z\sim 2.5$ to $\dot{\rho}_{\rm baryon}$/$\dot{\rho}_{\rm star}<$0.5 at $z\sim 0.5$, suggesting that massive galaxies are transforming from the "accretion dominated" phase to the "depletion dominated" phase from high$-z$ to low$-z$. The transition of these two phases occurs at $z\sim1.5$, which is consistent with the onset redshift of the decline of cosmic star formation rate density. This provides evidence to support the idea that the decline of cosmic star formation rate density since $z\sim1.5$ is mainly resulted from the decline of baryon net accretion rate and star formation quenching in galaxies., Comment: 7 pages, 3 figures, accepted by ApJL

The massive galaxy population above the characteristic Schechter mass M*~10^10.6 Msun contributes to about half of the total stellar mass in the local Universe. These massive galaxies usually reside in hot dark matter haloes above the critical shock-heating mass ~10^12 Msun, where the external cold gas supply to these galaxies is expected to be suppressed. When galaxies run out of their cold gas reservoir, they become dead and quiescent. Therefore, massive quiescent galaxies living in hot haloes are commonly believed to be gas-poor. Based on the data from SDSS, ALFALFA, GASS and COLD GASS surveys, here we show that the vast majority of the massive, quiescent, central disk galaxies in the nearby Universe have a remarkably large amount of cold atomic hydrogen gas, surprisingly similar to star-forming galaxies. Both star-forming and quiescent disk galaxies show identical symmetric double-horn HI spectra, indicating similar regularly rotating HI disks. Relative to their star-forming counterparts, massive quiescent central disk galaxies are quenched because of their significantly reduced molecular gas content, lower dust content, and lower star formation efficiency. Our findings reveal a new picture, which clearly demonstrates the detailed star-formation quenching process in massive galaxies and provides a stringent constraint on the physical mechanism of quenching., Comment: 10 pages, 4 figures (+2 figures in the appendix); accepted for publication in The Astrophysical Journal Letters

In the standard cosmological model, dark matter drives the structure formation and constructs potential wells within which galaxies may form. The baryon fraction in dark halos can reach the universal value (15.7%) in massive clusters and decreases rapidly as the mass of the system decreases. The formation of dwarf galaxies is sensitive both to baryonic processes and the properties of dark matter owing to the shallow potential wells in which they form. In dwarf galaxies in the Local Group, dark matter dominates the mass content even within their optical-light half-radii (r_e ~ 1 kpc). However, recently it has been argued that not all dwarf galaxies are dominated by dark matter. Here we report 19 dwarf galaxies that could consist mainly of baryons up to radii well beyond r_e, at which point they are expected to be dominated by dark matter. Of these, 14 are isolated dwarf galaxies, free from the influence of nearby bright galaxies and high dense environments. This result provides observational evidence that could challenge the formation theory of low-mass galaxies within the framework of standard cosmology. Further observations, in particular deep imaging and spatially-resolved kinematics, are needed to constrain the baryon fraction better in such galaxies., Comment: Published in Nature Astronomy on 25 November 2019, 27 pages including appendix, 7 figures

We study the gas inflow rate ($\zeta_{\rm inflow}$) and outflow rate ($\zeta_{\rm outflow}$) evolution of local Milky Way-mass star-forming galaxies (SFGs) since $z=1.3$. The stellar mass growth history of Milky Way-mass progenitor SFGs is inferred from the evolution of the star formation rate (SFR)$-$stellar mass ($M_{\ast}$) relation, and the gas mass ($M_{\rm gas}$) is derived using the recently established gas scaling relations. With the $M_{\ast}+M_{\rm gas}$ growth curve, the net inflow rate $\kappa$ is quantified at each cosmic epoch. At $z\sim 1.3$, $\kappa$ is comparable with the SFR, whereas it rapidly decreases to $\sim 0.15\times$SFR at $z=0$. We then constrain the average outflow rate $\zeta_{\rm outflow}$ of progenitor galaxies by modeling the evolution of their gas-phase metallicity. The best-fit $\zeta_{\rm outflow}$ is found to be $(0.5-0.8)\times$SFR. Combining $\kappa$ and $\zeta_{\rm outflow}$, we finally investigate the evolution of $\zeta_{\rm inflow}$ since $z=1.3$. We find that $\zeta_{\rm inflow}$ rapidly decreases by $\sim$80\% from $z=1.3$ to $z=0.5$. At $z<0.5$, $\zeta_{\rm inflow}$ continuously decreases but with a much lower decreasing rate. Implications of these findings on galaxy evolution are discussed., Comment: 12 pages, 9 figures, accepted by ApJ

Star-forming galaxies can in principle be transformed into passive systems by a multitude of processes that quench star formation, such as the halting of gas accretion (starvation) or the rapid removal of gas in AGN-driven outflows. However, it remains unclear which processes are the most significant, primary drivers of the SF-passive bimodality. We address this key issue in galaxy evolution by studying the chemical properties of 80,000 local galaxies in SDSS DR7. In order to distinguish between different quenching mechanisms, we analyse the stellar metallicities of star-forming, green valley and passive galaxies. We find that the significant difference in stellar metallicity between passive galaxies and their star-forming progenitors implies that for galaxies at all masses, quenching must have involved an extended phase of starvation. However, some form of gas ejection also has to be introduced into our models to best match the observed properties of local passive galaxies, indicating that, while starvation is likely to be the prerequisite for quenching, it is the combination of starvation and outflows that is responsible for quenching the majority of galaxies. Closed-box models indicate that the duration of the quenching phase is 2-3 Gyr, with an $e$-folding time of 2-4 Gyr, after which further star formation is prevented by an ejective/heating mode. Alternatively, leaky-box models find a longer duration for the quenching phase of 5-7 Gyr and an $e$-folding time of $\sim$1 Gyr, with outflows becoming increasingly important with decreasing stellar mass. Finally, our analysis of local green valley galaxies indicates that quenching is slower in the local Universe than at high-redshift., Comment: 32 pages, 20 figures, 1 table. Accepted for publication in MNRAS