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The Square Kilometre Array mid-frequency array will enable high-redshift detections of neutral hydrogen (H i) emission in galaxies, providing important constraints on the evolution of cold gas in galaxies over cosmic time. Strong gravitational lensing will push back the H i emission frontier towards cosmic noon (⁠|$z\sim 2$|⁠), as has been done for all prominent spectral lines in the interstellar medium of galaxies. Chakraborty & Roy report a |$z=1.3$| H i emission detection towards the well-modelled, galaxy-scale gravitational lens, SDSS J0826+5630. We carry out H i source modelling of the system and find that their claimed H i magnification, |$\mu _{\rm H\, {\small I}} = 29 \pm 6$|⁠ , requires an H i disc radius of |$\lesssim\!\! 1.5$| kpc, which implies an implausible mean H i surface mass density in excess of |$\Sigma _{\rm H\, {\small I}} > 2000 \ \rm{ M}_\odot \, \rm{pc}^{-2}$|⁠. This is several orders of magnitude above the highest measured peak values (⁠|$\Sigma _{\rm H\, {\small I}} \sim 10~{\rm M}_\odot \, {\rm pc}^{-2}$|⁠), above which H i is converted into molecular hydrogen. Our re-analysis requires this to be the highest H i mass galaxy known (⁠|$M_{\rm H\, {\small I}} \sim 10^{11} \ \mathrm{ M}_\odot$|⁠), as well as strongly lensed, the latter having a typical probability of the order of 1 in 103–104. We conclude that the claimed detection is spurious. [ABSTRACT FROM AUTHOR]

We compare the l-galaxies semi-analytic model to deep observational data from the UKIDSS Ultra Deep Survey (UDS) across the redshift range 0.5 < z < 3. We find that the overabundance of low-mass, passive galaxies at high redshifts in the model can be attributed solely to the properties of 'orphan' galaxies, i.e. satellite galaxies where the simulation has lost track of the host dark matter sub-halo. We implement a simple model that boosts the star formation rates in orphan galaxies by matching them to non-orphaned satellite galaxies at a similar evolutionary stage. This straightforward change largely addresses the discrepancy in the low-mass passive fraction across all redshifts. We find that the orphan problem is somewhat alleviated by higher resolution simulations, but the preservation of a larger gas reservoir in orphans is still required to produce a better fit to the observed space density of low-mass passive galaxies. Our findings are also robust to the precise definition of the passive galaxy population. In general, considering the vastly different prescriptions used for orphans in semi-analytic models, we recommend that they are analysed separately from the resolved satellite galaxy population, particularly with JWST observations reigniting interest in the low-mass regime in which they dominate. [ABSTRACT FROM AUTHOR]

Observations show a tight correlation between the stellar mass of galaxies and their gas-phase metallicity (MZR). This relation evolves with redshift, with higher redshift galaxies being characterized by lower metallicities. Understanding the physical origin of the slope and redshift evolution of the MZR may provide important insight into the physical processes underpinning it: star formation, feedback, and cosmological inflows. While theoretical models ascribe the shape of the MZR to the lower efficiency of galactic outflows in more massive galaxies, what drives its evolution remains an open question. In this letter, we analyse how the MZR evolves over z  = 0–3, combining results from the FIREbox cosmological volume simulation with analytical models. Contrary to a frequent assertion in the literature, we find that the evolution of the gas fraction does not contribute significantly to the redshift evolution of the MZR. Instead, we show that the latter is driven by the redshift dependence of the inflow metallicity, outflow metallicity, and mass loading factor, whose relative importance depends on stellar mass. These findings also suggest that the evolution of the MZR is not explained by galaxies moving along a fixed surface in the space spanned by stellar mass, gas-phase metallicity, and star formation rate. [ABSTRACT FROM AUTHOR]

We present a sample of 950 edge-on spiral galaxies found with the use of an artificial neural network in the Hubble Space Telescope COSMOS field. This is currently the largest sample of distant edge-on galaxies. For all galaxies we analysed the 2D brightness distributions in the F814W filter and measured the radial and vertical exponential scales (h and hz correspondingly) of the brightness distribution. By comparing the characteristics of distant galaxies with those of nearby objects, we conclude that thin stellar discs with h / hz ≥ 10 at z ≈ 0.5 should be rarer than today. Both exponential scales of the stellar disc show evidence of luminosity-dependent evolution: in faint galaxies the h and hz values do not change with z , in bright (and massive) spiral galaxies both scales, on average, grow towards our epoch. [ABSTRACT FROM AUTHOR]

Double bars make up a significant fraction of barred galaxies. We propose a new formation scenario for double bars that involves tidal interactions. We demonstrate the viability of this scenario using two examples of simulated galaxies from run TNG50-1 of the IllustrisTNG project. In the proposed scenario the inner bar forms first, either in isolation, via instabilities, or through previous tides. The outer bar forms later from the material that is tidally distorted by a strong interaction. The inner and outer bars formed this way rotate with different pattern speeds and can be mistaken for a single bar when their phases align. The double-barred structure is stable and can last for at least 3 Gyr. The inner bars of the tidally induced double bars can also have big sizes, which can possibly explain the origin of sizable inner bars recently found in some galaxies. [ABSTRACT FROM AUTHOR]

We present clear and direct evidence of the pre-processing effect of group galaxies falling into clusters in the local Universe (z ≲ 0.1). We start with a sample of 238 clusters, from which we select 153 with N 200 ≥ 20. We considered 1641 groups within the turnaround radius (∼5 × R 200) of these 153 clusters. There are 6654 individual cluster galaxies and 4133 group galaxies within this radius. We considered two control samples of galaxies, in isolated groups and in the field. The former comprises 2601 galaxies within 1606 isolated groups , and the latter has 4273 field objects. The fraction of star-forming galaxies in infalling groups has a distinct clustercentric behaviour in comparison to the remaining cluster galaxies. Even at 5 × R 200 the group galaxies already show a reduced fraction of star-forming objects. At this radius, the results for the individual cluster galaxies are actually compatible with the field. That is strong evidence that the group environment is effective to quench the star formation prior to the cluster arrival. The group star-forming fraction remains roughly constant inwards, decreasing significantly only within the cluster R 200 radius. We have also found that the pre-processing effect depends on the group mass (indicated by the number of members). The effect is larger for more massive groups. However, it is significant even for pairs and triplets. Finally, we find evidence that the time-scale required for morphological transformation is larger than the one for quenching. [ABSTRACT FROM AUTHOR]

We study a compact nucleus embedded in an early-type dwarf galaxy, MATLAS-167, which is in the process of disruption by the tidal force of the neighbouring giant S0 galaxy, NGC 936, in a group environment. Using the imaging data of the MATLAS survey, we analyse the stellar tidal tail of MATLAS-167 and its central compact nucleus, designated as NGC 936_UCD. We find that NGC 936_UCD has a luminosity of Mg = −11.43 ± 0.01 mag and a size of 66.5 ± 17 pc, sharing the global properties of ultra-compact dwarf galaxies (UCDs) but significantly larger and brighter compared to the typical UCD populations observed in the Virgo cluster. By integrating the total luminosity of both the tidal stream and MATLAS-167, we estimate that the disrupted dwarf progenitor possesses a luminosity of Mg = −15.92 ± 0.06 mag, a typical bright early-type dwarf galaxy luminosity. With the help of the optical spectrum observed by the SDSS survey, we derive the simple stellar population properties of NGC 936_UCD: a light-weighted age of 5.6 ± 0.7 Gyr and metallicity of [Z/H] = −0.83 ± 0.3 dex. Our findings suggest that tidal threshing is a possible formation mechanism of bright UCD populations in close proximity to giant galaxies. [ABSTRACT FROM AUTHOR]

Motivated by spectroscopic confirmation of three overdense regions in the COSMOS field at z ∼ 3.35, we analyse the uniquely deep multiwavelength photometry and extensive spectroscopy available in the field to identify any further related structure. We construct a three-dimensional density map using the Voronoi tesselation Monte Carlo method and find additional regions of significant overdensity. Here, we present and examine a set of six overdense structures at 3.20 < z < 3.45 in the COSMOS field, the most well-characterized of which, PCl J0959 + 0235, has 80 spectroscopically confirmed members and an estimated mass of 1.35 × 1015 M⊙, and is modelled to virialize at z ∼ 1.5−2.0. These structures contain 10 overdense peaks with >5σ overdensity separated by up to 70 cMpc, suggestive of a proto-supercluster similar to the Hyperion system at z ∼ 2.45. Upcoming photometric surveys with JWST such as COSMOS-Web, and further spectroscopic follow-up will enable more extensive analysis of the evolutionary effects that such an environment may have on its component galaxies at these early times. [ABSTRACT FROM AUTHOR]

We investigate the clustering properties of 3 < z < 5 candidate passive galaxies from the Merlin et al. (2019) sample residing in the GOODS-North (35 sources) and GOODS-South (33 sources) fields. Within the large uncertainties due to the paucity of sources we do not detect clustering signal in GOODS-North, while this is present in GOODS-South, highlighting the importance of the effects of cosmic variance. The estimated correlation length in GOODS-South is |$r_0=12^{+4}_{-5}$|  Mpc, while the estimated minimum mass for a halo capable to host one of such high-redshift quenched galaxies is log10(M min/M⊙) = 13.0 ± 0.3, once also the constraints from their space density are taken into account. Both values are compatible with the results from GOODS-North. Putting the above findings in a cosmological context, these suggest no evolution of the dark matter content of the hosts of passive galaxies during the past 12.5 Gyr, i.e. during more than 90 per cent of the age of the Universe. We discuss possible scenarios for the observed trend. [ABSTRACT FROM AUTHOR]

The excellent sensitivity and optimum resolution of LoTSS DR2 at 144 MHz has enabled us to discover a giant radio galaxy (J1225+4011) with three distinct episodes of jet activity, making it a member of a class of objects called triple-double radio galaxies (TDRGs). The source extends overall up to 1.35 Mpc in projected size, with the second episode extending to 572 kpc, and the inner episode to 118 kpc. J1225+4011 is only the fourth radio source showing a triple-double radio structure. All four sources have overall sizes greater than 700 kpc, making them giants. We also present the LoTSS 144 MHz map of the TDRG J0929+4146 and report its updated size. Lastly, we have summarized and discussed the radio properties of all TDRGs for the first time to understand their growth and evolution. Our observations suggest that the power of their jets may decrease with time. [ABSTRACT FROM AUTHOR]

The circumgalactic medium (CGM) is the most massive baryonic component of a spiral galaxy, shock heated to about 106 K for an |$\rm L^{\star }$| galaxy. The CGM of the Milky Way has been well-characterized through X-ray absorption line spectroscopy. However, the paucity of bright background sources makes it challenging to probe the CGM of external galaxies. Previously, using broad O  vi absorption as a signpost, we successfully detected the CGM of one galaxy in X-rays. Here we report on the detection of the O  vii K α absorption line at the redshift of a spiral galaxy at z ≈ 0.225, using 1.2 Ms of Chandra observations. This is a robust detection, clearly showing the presence of the hot gas. The mass in the hot phase is at least an order of magnitude larger than that in the cooler phases detected in the UV. The presence of hot gas 116 h−1 kpc from the centre of this galaxy provides credence to the existence of the extended CGM of the Milky Way. There has been a report of the detection of O  vii absorption from the warm-hot intergalactic medium in this sightline, using stacking analysis on older data set. We argue that the absorption line is from the CGM of the z ≈ 0.225 galaxy instead. [ABSTRACT FROM AUTHOR]

Using recent empirical constraints on the dark matter halo–galaxy–supermassive black hole (SMBH) connection from z  = 0–7, we infer how undermassive, typical, and overmassive SMBHs contribute to the quasar luminosity function (QLF) at z  = 6. We find that beyond L bol = 5 × 1046 erg s−1, the z  = 6 QLF is dominated by SMBHs that are at least 0.3 dex above the z  = 6 median M • –M * relation. The QLF is dominated by typical SMBHs (i.e. within ±0.3 dex around the M •– M * relation) at L bol ≲ 1045 erg s−1. At z ∼ 6, the intrinsic M • –M * relation for all SMBHs is slightly steeper than the z  = 0 scaling, with a similar normalization at |$M_* \sim 10^{11} \, \mathrm{M}_\odot$|⁠. We also predict the M • –M * relation for z  = 6 bright quasars selected by different bolometric luminosity thresholds, finding very good agreement with observations. For quasars with L bol > 3 × 1046 (1048) erg s−1, the scaling relation is shifted upwards by ∼0.35 (1.0) dex for 1011M⊙ galaxies. To accurately measure the intrinsic M • –M * relation, it is essential to include fainter quasars with L bol ≲ 1045 erg s−1. At high redshifts, low-luminosity quasars are thus the best targets for understanding typical formation paths for SMBHs in galaxies. [ABSTRACT FROM AUTHOR]

Despite its crucial role in galaxy evolution, the complex circumgalactic medium (CGM) remains underexplored. Although, it is known to be multiphase, the importance of the molecular gas phase to the total CGM mass budget is, to date, unconstrained. We present the first constraints on the molecular gas covering fraction in the CGM of low-redshift galaxies, using measurements of CO column densities along sightlines towards mm-bright background quasars with intervening galaxies. We do not detect molecular absorption against the background quasars. For the individual, low-redshift, 'normal' galaxy haloes probed here, we can therefore rule out the presence of an extremely molecular gas-rich CGM, as recently reported in high-redshift protoclusters and around luminous active galactic nuclei. We also set statistical limits on the volume filling factor of molecular material in the CGM as a whole, and as a function of radius. Interstellar medium-like molecular clouds of ∼30 pc in radius with column densities of N (CO) ≳ 1016 cm−2 have volume filling factors of <0.2 per cent. Large-scale smooth gas reservoirs are ruled out much more stringently. The development of this technique in the future will allow deeper constraining limits to be set on the importance (or unimportance) of molecular gas in the CGM. [ABSTRACT FROM AUTHOR]

The bright end of the rest-frame ultraviolet luminosity function (UVLF) of high-redshift galaxies is modified by gravitational lensing magnification bias. Motivated by recent discoveries of very high- z galaxies with JWST , we study the dependence of magnification bias on the finite size of sources at 6 < z < 14. We calculate the magnification probability distributions and use these to calculate the magnification bias assuming a rest-frame Schechter UVLF for galaxies at redshift 6 < z < 14. We find that the finite size of bright high-redshift galaxies together with lens ellipticity significantly suppresses magnification bias, producing an observed bright end which declines more sharply than the power law resulting from assumption of point sources. By assuming a luminosity–size relation for the source population and comparing with the observed z  = 6 galaxy luminosity function from Harikane et al. (2022), we show that the UVLF can be used to set mild constraints on the galaxies intrinsic size, favouring smaller galaxies compared to the fiducial luminosity–size relation. In the future, wide surveys using Euclid and Roman Space Telescope will place stronger constraints. We also tabulate the maximum magnification possible as a function of source size and lens ellipticity. [ABSTRACT FROM AUTHOR]

Deriving oxygen abundances from the electron temperature (hereafter the Te method) is the gold standard for extragalactic metallicity studies. However, unresolved temperature fluctuations within individual H ii regions and across different H ii regions throughout a galaxy can bias metallicity estimates low, with a magnitude that depends on the underlying and typically unknown temperature distribution. Using a toy model, we confirm that computing Te-based metallicities using the temperature derived from the [O iii] λ4363/λ5007 or [O ii] λλ7320, 7330/[O ii] λλ3727 ratio ('ratio temperature', Tratio) results in an underprediction of metallicity when temperature fluctuations are present. In contrast, using the unobservable 'line temperatures' (Tline) that provide the mean electron and ion density-weighted emissivity yields an accurate metallicity estimate. To correct this bias in low-mass galaxies, we demonstrate an example calibration of a relation between Tratio and Tline based on a high-resolution (4.5 pc) ramses-rtz simulation of a dwarf galaxy that self-consistently models the formation of multiple H ii regions and ion temperature distribution in a galactic context. Applying this correction to the low-mass end of the mass–metallicity relation shifts its normalization up by 0.18 dex on average and flattens its slope from 0.87 to 0.58, highlighting the need for future studies to account for, and correct, this bias. [ABSTRACT FROM AUTHOR]

In this letter, we explore the quiescent lives of central galaxies using the Semi-Analytical Galaxy Evolution galaxy model and Uchuu dark matter simulation. We ask three questions: (1) How much of a galaxy's life is spent in quiescence? (2) How often do galaxies transit off the main sequence? (3) What is the typical duration of a quiescent phase? We find that the low- and high-mass galaxies spend the highest fraction of their lives in quiescence: 45 ± 19 per cent for log10(Mstar) < 9.0 (3.68 ± 1.80 Gyr) and 26 ± 25 per cent for log10(Mstar) > 11.5 (3.46 ± 3.30 Gyr), falling to 7 ± 13 per cent for galaxies in-between (0.82 ± 1.57 Gyr). Low-mass galaxies move in and out of quiescence frequently, 2.8 ± 1.3 times on average, though only for short periods, 1.49 ± 1.04 Gyr. This can be traced to the influence of supernova feedback on their quite stochastic evolution. Galaxies of higher mass have fewer quiescent periods, ∼0.7 ± 0.9, and their length increases with mass, peaking at 1.97 ± 2.27 Gyr. However, our high-mass population comprises star-forming and quiescent galaxies with diverging evolutionary paths, so the actual time may be even longer. These high-mass trends are driven by radio-mode feedback from supermassive black holes, which, once active, tend to remain active for extended periods. [ABSTRACT FROM AUTHOR]

The correlation between galaxies' integrated stellar masses and star formation rates (the 'star formation main sequence', SFMS) is a well-established scaling relation. Recently, surveys have found a relationship between the star formation rate (SFR) and stellar mass surface densities on kpc and sub-kpc scales (the 'resolved SFMS', rSFMS). In this work, we demonstrate that the rSFMS emerges naturally in Feedback In Realistic Environments 2 (FIRE-2) zoom-in simulations of Milky Way-mass galaxies. We make SFR and stellar mass maps of the simulated galaxies at a variety of spatial resolutions and star formation averaging time-scales and fit the rSFMS using multiple methods from the literature. While the absolute value of the SFMS slope (αMS) depends on the fitting method, the slope is steeper for longer star formation time-scales and lower spatial resolutions regardless of the fitting method employed. We present a toy model that quantitatively captures the dependence of the simulated galaxies' αMS on spatial resolution and use it to illustrate how this dependence can be used to constrain the characteristic mass of star-forming clumps.

Rare giant low surface brightness galaxies (gLSBGs) act as a stress test for the current galaxy formation paradigm. To answer the question 'How rare are they?', we estimate their volume density in the local Universe. A visual inspection of 120 deg2 covered by deep Subaru Hyper Suprime-Cam data was performed independently by four team members. We detected 42 giant disky systems (30 of them isolated) at z ≤ 0.1 with either g -band 27.7 mag arcsec−2 isophotal radius or four disc scale lengths 4 h ≥ 50 kpc, 37 of which (including 25 isolated) had low central surface brightness (μ0, g ≥ 22.7 mag arcsec−2). This corresponds to volume densities of 4.70 × 10−5 Mpc−3 for all galaxies with giant extended discs and 4.04 × 10−5 Mpc−3 for gLSBGs, which converts to ∼12 700 such galaxies in the entire sky out to z < 0.1. These estimates agree well with the result of the Evolution and Assembly of GaLaxies and their Environments (EAGLE) cosmological hydrodynamical simulation. Giant disky galaxies represent the large-sized end of the volume density distribution of normal-sized spirals, suggesting the non-exceptional nature of giant discs. We observe a high active galactic nucleus fraction among the newly found gLSBGs. [ABSTRACT FROM AUTHOR]

Recent attempts to detect [O  iii ] 88 |$\, \mu$| m emission from super-early (z > 10) galaxy candidates observed by JWST have been unsuccessful. Non-detections can be either due to wrong photometric redshifts or to the faintness of the line in such early systems. By using zoom-in simulations, we show that if redshifts of these galaxies are confirmed, they are faint and mostly fall below the local metal-poor |$\rm [O\, {\small III}]-SFR$| relation as a result of their low ionization parameter, U ion ≲ 10−3. Such low U ion values are found in galaxies that are in an early assembly stage, and whose stars are still embedded in high-density natal clouds. However, the most luminous galaxy in our sample (⁠|$\rm {log}[L_{\rm {[O\, {\small III}]}}/\mathrm{L}_\odot ] = 8.4$|⁠ , U ion ≈ 0.1) could be detected by ALMA in only 2.8 h. [ABSTRACT FROM AUTHOR]

We report the discovery of a rare early-type dwarf galaxy (dE), SDSS J125651.47+163024.2 (hereafter, dE1256), possessing a tidal feature that was likely built up by accretion of an even smaller dwarf galaxy. dE1256 is located in a nearly isolated environment, at the outskirt of the Virgo cluster. A detailed morphological examination reveals that the accreted stellar population is mainly deposited in the outer part of dE1256, where the tidal tail is most prominent. The inner part of dE1256 is perfectly modelled with a simple Sérsic function of index n = 0.63 and half-light radius Rh = 0.6 kpc, but in contrast, the entire galaxy has a size of Rh = 1.2 kpc. The mass ratio between the host and the putative accreted dwarf galaxy is calculated to be 5:1, assuming that the observed two components, inner Sérsic and outer tidal tail residual, represent the host's and accreted galaxy's stellar populations, respectively. We suggest that while the accretion contributes only 20 per cent of the overall stellar population, the size of dE1256 grew by a factor of two via the accretion event. Our results provide, for the first time, strong observational evidence that a dE is undergoing a two-phase growth, a common phenomenon for massive galaxies. [ABSTRACT FROM AUTHOR]

Bar formation in cosmological simulations of galaxy formation remains challenging. It was previously shown that the fraction of barred galaxies at low stellar masses (M * < 1010.5 M⊙) in TNG50 is too low compared to the observations. Here, we highlight another tension, also observed at higher stellar masses, namely that barred galaxies in TNG50 appear to be maximal discs, in the sense that the majority of the gravitational acceleration is accounted for by baryons at the peak radius of the baryonic rotation curve, while observations account for a substantial fraction of barred submaximal discs. In this letter, we compare the barred fraction of submaximal discs in the local Universe from the SPARC catalogue with that in the TNG50 simulation. We show that, although SPARC tends to select against barred galaxies, the fraction of barred submaximal discs in this data set is significantly larger than in TNG50. This result adds to the list of challenges related to predicting the right statistics and properties of barred galaxies in ΛCDM simulations of galaxy formation. [ABSTRACT FROM AUTHOR]

We have used ALMA imaging (resolutions 0.1–0.4 arcsec) of ground and vibrationally excited lines of HCN and HC3N toward the nucleus of NGC 4945 to trace the protostellar phase in super star clusters (proto-SSC). Out of the 14 identified SSCs, we find that eight are in the proto-SSC phase showing vibrational HCN emission with five of them also showing vibrational HC3N emission. We estimate proto-SSC ages of 5–9.7 × 104 yr. The more evolved ones, with only HCN emission, are close to reach the zero-age main sequence (ZAMS; ages ≳105 yr). The excitation of the parental cloud seems to be related to the SSC evolutionary stage, with high (∼65 K) and low (∼25 K) rotational temperatures for the youngest proto and ZAMS SSCs, respectively. Heating by the H  ii regions in the SSC ZAMS phase seems to be rather local. The youngest proto-SSCs are located at the edges of the molecular outflow, indicating SSC formation by positive feedback in the shocked regions. The proto-SSCs in NGC 4945 seem to be more evolved than in the starburst galaxy NGC 253. We propose that sequential SSC formation can explain the spatial distribution and different ages of the SSCs in both galaxies. [ABSTRACT FROM AUTHOR]

A wealth of extragalactic populations completely missed at UV-optical wavelengths has been identified in the last decade, combining the deepest HST and Spitzer observations. These dark sources are thought to be dusty and star-forming systems at 3 < z < 5, and major contributors to the stellar mass build up. In this letter, we report an investigation of the deep JWST survey in the SMACS0723 cluster, analysing NIRCam and MIRI images. We search for sources in the F444W band that are undetected in the F200W catalogues. We characterize the properties of these sources via detailed Spectral Energy Distribution (SED) modelling, accounting for a wide set of parameters and star formation histories, after a careful determination of their photometry. Among a robust sample of 20 candidates, we identify a mixed population of very red sources. We highlight the identification of evolved systems, with stellar masses M * ∼ 109–11 M⊙ at 8 < z < 13 characterized by unexpectedly important dust content at those epochs (AV up to ∼5.8 mag), challenging current model predictions. We further identify an extremely red source (F200W-F440W ∼ 7 mag) that can be reproduced only by the spectrum of a passive, quenched galaxy of M * ∼ 1011.56 M⊙ at z  ∼ 5, filled of dust (AV  ∼ 5 mag). [ABSTRACT FROM AUTHOR]

We measure and compare the pattern speeds of vertical breathing, vertical bending, and spiral density waves in two isolated N-body+SPH simulations, using windowed Fourier transforms over |$1 \mbox{$\:{\rm Gyr}$}$| time intervals. We show that the pattern speeds of the breathing waves match those of the spirals but are different from those of the bending waves. We also observe matching pattern speeds between the bar and breathing waves. Our results not only strengthen the case that, throughout the disc, breathing motions are driven by spirals but indeed that the breathing motions are part and parcel of the spirals. [ABSTRACT FROM AUTHOR]

We analysed the high-resolution (up to ∼0.2 arcsec) ALMA CO (2–1) and 1.3 mm dust continuum data of eight gas-rich post-starburst galaxies (PSBs) in the local Universe, six of which had been studied by a recent work. In contrast to this study reporting the detections of extraordinarily compact (i.e. unresolved) reservoirs of molecular gas in the six PSBs, our visibility-plane analysis resolves the CO (2–1) emission in all eight PSBs with effective radii (R e, CO) of |$0.8_{-0.4}^{+0.9}$|  kpc, typically consisting of gaseous components at both circumnuclear and extended disc scales. With this new analysis, we find that the CO sizes of gas-rich PSBs are compact with respect to their stellar sizes (median ratio |$=0.43_{-0.21}^{+0.27}$|⁠), but comparable to the sizes of the gas discs seen in local luminous infrared galaxies (LIRGs) and early-type galaxies. We also find that the CO-to-stellar size ratio of gas-rich PSBs is potentially correlated with the gas depletion time-scale, placing them as transitional objects between LIRGs and early-type galaxies from an evolutionary perspective. Finally, the star formation efficiency of the observed PSBs appear consistent with those of star-forming galaxies on the Kennicutt–Schmidt relation, showing no sign of suppressed star formation from turbulent heating. [ABSTRACT FROM AUTHOR]

Active galactic nucleus (AGN) feedback during galaxy merger has been the most favoured model to explain black hole–galaxy co-evolution. However, how the AGN-driven jet/wind/radiation is coupled with the gas of the merging galaxies, which leads to positive feedback, momentarily enhanced star formation, and subsequently negative feedback, a decline in star formation, is poorly understood. Only a few cases are known where the jet and companion galaxy interaction leads to minor off-axis distortions in the jets and enhanced star formation in the gas-rich minor companions. Here, we briefly report one extraordinary case, RAD12, discovered by RAD@home citizen science collaboratory, where for the first time a radio jet–driven bubble (∼ 137 kpc) is showing a symmetric reflection after hitting the incoming galaxy which is not a gas-rich minor but a gas-poor early-type galaxy in a major merger. Surprisingly, neither positive feedback nor any radio lobe on the counter jet side, if any, is detected. It is puzzling if RAD12 is a genuine one-sided jet or a case of radio lobe trapped, compressed and re-accelerated by shocks during the merger. This is the first imaging study of RAD12 presenting follow-up with the Giant Metrewave Radio Telescope , archival MeerKAT radio data and Canada-France-Hawaii Telescope optical data. [ABSTRACT FROM AUTHOR]

Galaxy mergers trigger both star formation and accretion on to the central supermassive black hole. As a result of subsequent energetic feedback processes, it has long been proposed that star formation may be promptly extinguished in galaxy merger remnants. However, this prediction of widespread, rapid quenching in late stage mergers has been recently called into question with modern simulations and has never been tested observationally. Here we perform the first empirical assessment of the long-predicted end phase in the merger sequence. Based on a sample of ∼500 post-mergers identified from the Ultraviolet Near Infrared Optical Northern Survey (UNIONS), we show that the frequency of post-merger galaxies that have rapidly shutdown their star formation following a previous starburst is 30–60 times higher than expected from a control sample of non-merging galaxies. No such excess is found in a sample of close galaxy pairs, demonstrating that mergers can indeed lead to a rapid halt to star formation, but that this process only manifests after coalescence. [ABSTRACT FROM AUTHOR]

We present deep observations of CO (3–2) from the Cloverleaf lensed quasar-starburst at z  = 2.56. We discover a 4–5 times less massive companion at a projected distance of 33 kpc from the Cloverleaf host galaxy. The galaxies are connected by a bridge of CO emission, indicating that they are interacting and that the companion is being stripped by the Cloverleaf. We also find evidence for fast molecular gas in the spectral line of the Cloverleaf that may be an outflow induced by stellar or quasar feedback. All of these features may be ubiquitous among quasars and only detected here with the help of gravitational lensing and the sensitivity of the data. Overall, these findings agree with galaxy formation scenarios that predict gas-rich mergers play a key role in quasar triggering, starburst triggering, and the formation of compact spheroids. [ABSTRACT FROM AUTHOR]

Feedback, in particular from active galactic nuclei (AGNs), is believed to play a crucial role in the evolution of galaxies. In the local Universe, many galaxies with an AGN are indeed observed to reside in the so-called green valley, usually interpreted as a transition phase from a blue star-forming to a red quenched state. We use data from the Sloan Digital Sky Survey to show that such an interpretation requires substantial revision. Optically selected nearby AGN galaxies follow exponentially declining star formation histories, as normal galaxies of similar stellar and dark matter halo mass, reaching in the recent past (∼0.1 Gyr ago) star formation rate levels consistent with a quiescent population. However, we find that local AGN galaxies have experienced a sudden increase in their star formation rate, unfolding on time-scales similar to those typical of AGN activity, suggesting that both star formation and AGN activity were triggered simultaneously. We find that this quenching followed by an enhancement in the star formation rate is common to AGN galaxies and more pronounced in early-type galaxies. Our results demonstrate that local AGN galaxies are not just a simple transition type between star-forming and quiescent galaxies as previously postulated. [ABSTRACT FROM AUTHOR]

We introduce massive black holes (BHs) in the Feedback In Realistic Environments (FIRE) project and perform high-resolution cosmological hydrodynamic simulations of quasar-mass haloes [Mhalo(z = 2) ≈ 1012.5M⊙] down to z = 1. These simulations model stellar feedback by supernovae, stellar winds and radiation, and BH growth using a gravitational torque-based prescription tied to the resolved properties of galactic nuclei.We do not include BH feedback. We show that early BH growth occurs through short (≲1Myr) accretion episodes that can reach or even exceed the Eddington rate. In this regime, BH growth is limited by bursty stellar feedback continuously evacuating gas from galactic nuclei, and BHs remain undermassive in low-mass galaxies relative to the local MBH-Mbulgerelation. BH growth is more efficient at later times, when the nuclear stellar potential retains a significant gas reservoir, star formation becomes less bursty and galaxies settle into a more ordered state. BHs rapidly converge on to the observed scaling relations when the host reaches Mbulge ~1010M⊙. We show that resolving the effects of stellar feedback on the gas supply in the inner ~100 pc of galaxies is necessary to accurately capture the growth of central BHs. Our simulations imply that bursty stellar feedback has important implications for BH-galaxy relations, AGN demographics and time variability, the formation of early quasars and massive BH mergers.

Near-field cosmology - using detailed observations of the Local Group and its environs to study wide-ranging questions in galaxy formation and dark matter physics - has become a mature and rich field over the past decade. There are lingering concerns, however, that the relatively small size of the present-day Local Group (~2Mpc diameter) imposes insurmountable samplevariance uncertainties, limiting its broader utility.We consider the region spanned by the Local Group's progenitors at earlier times and show that it reaches 3 arcmin ≈ 7 comoving Mpc in linear size (a volume of ≈350 Mpc3) at z = 7. This size at early cosmic epochs is large enough to be representative in terms of the matter density and counts of dark matter haloes with Mvir(z = 7) ≲ 2 × 109M⊙. The Local Group's stellar fossil record traces the cosmic evolution of galaxies with 103 ≲ M*(z = 0)/M⊙ ≲ 109 (reaching M1500 > -9 at z ~ 7) over a region that is comparable to or larger than the Hubble Ultra-Deep Field (HUDF) for the entire history of the Universe. In the JWST era, resolved stellar populations will probe regions larger than the HUDF and any deep JWST fields, further enhancing the value of near-field cosmology.

We report ALMA Band 9 continuum observations of the normal, dusty star-forming galaxy A1689-zD1 at z = 7.13, resulting in a ∼4.6 σ detection at 702 GHz. For the first time, these observations probe the far-infrared spectrum shortward of the emission peak of a galaxy in the Epoch of Reionization (EoR). Together with ancillary data from earlier works, we derive the dust temperature, Td , and mass, M d, of A1689-zD1 using both traditional modified blackbody spectral energy density fitting, and a new method that relies only on the [C  ii ] 158 μm line and underlying continuum data. The two methods give |$T_{\rm d} = (42^{+13}_{-7}, 40^{+13}_{-7}$|⁠) K, and |$M_{\rm d} = (1.7^{+1.3}_{-0.7}, 2.0^{+1.8}_{-1.0})\, \times {}\, 10^{7} \, \mathrm{ M}_{\odot }$|⁠. Band 9 observations improve the accuracy of the dust temperature (mass) estimate by ∼50 per cent (6 times). The derived temperatures confirm the reported increasing T d-redshift trend between z = 0 and 8; the dust mass is consistent with a supernova origin. Although A1689-zD1 is a normal UV-selected galaxy, our results, implying that ∼85 per cent of its star-formation rate is obscured, underline the non-negligible effects of dust in EoR galaxies. [ABSTRACT FROM AUTHOR]

Turbulent mixing layers (TMLs) are ubiquitous in multiphase gas. They can potentially explain observations of high ions such as O  vi , which have significant observed column densities despite short cooling times. Previously, we showed that global mass, momentum, and energy transfer between phases mediated by TMLs is not sensitive to details of thermal conduction or numerical resolution. By contrast, we show here that observables such as temperature distributions, column densities, and line ratios are sensitive to such considerations. We explain the reason for this difference. We develop a prescription for applying a simple 1D conductive-cooling front model which quantitatively reproduces 3D hydrodynamic simulation results for column densities and line ratios, even when the TML has a complex fractal structure. This enables subgrid absorption and emission line predictions in large scale simulations. The predicted line ratios are in good agreement with observations, while observed column densities require numerous mixing layers to be pierced along a line of sight. [ABSTRACT FROM AUTHOR]

The scaling relation between stellar mass (M *) and physical effective radius (r e) has been well studied using wide spectroscopic surveys. However, these surveys suffer from severe surface brightness incompleteness in the dwarf galaxy regime, where the relation is poorly constrained. In this study, I use a Bayesian empirical model to constrain the power-law exponent β of the M *– r e relation for late-type dwarfs (⁠|$10^{7} \le$| M */M⊙ |$\le 10^{9}$|⁠) using a sample of 188 isolated low surface brightness (LSB) galaxies, accounting for observational incompleteness. Surprisingly, the best-fitting model (β = 0.40 ± 0.07) indicates that the relation is significantly steeper than would be expected from extrapolating canonical models into the dwarf galaxy regime. Nevertheless, the best fitting M*–r e relation closely follows the distribution of known dwarf galaxies. These results indicate that extrapolated canonical models overpredict the number of large dwarf (i.e. LSB) galaxies, including ultra-diffuse galaxies (UDGs), explaining why they are overproduced by some semi-analytic models. The best-fitting model also constrains the power-law exponent of the physical size distribution of UDGs to |$n\mathrm{[dex^{-1}]}\propto r_{\mathrm{ e}}^{3.54\pm 0.33}$|⁠ , consistent to within 1σ of the corresponding value in cluster environments and with the theoretical scenario in which UDGs occupy the high-spin tail of the normal dwarf galaxy population. [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]

We present a pixelized source reconstruction method applied on integral field spectroscopic observations of gravitationally lensed galaxies. We demonstrate the effectiveness of this method in a case study on the clumpy morphology of a z ∼ 2 lensed galaxy behind a group-scale lens. We use a Bayesian forward source modelling approach to reconstruct the surface brightness distribution of the source galaxy on a uniformly pixelized grid while accounting for the image point spread function. The pixelated approach is sensitive to clump sizes down to 100 pc and resolves smaller clump sizes with an improvement in the signal-to-noise ratio by almost a factor of 10 compared with more traditional ray-tracing approaches. [ABSTRACT FROM AUTHOR]

Many active galactic nuclei (AGN) surveys rely on optical emission line signatures for robust source classification. There are, however, examples of luminous AGN candidates lacking such signatures, including those from the narrow-line region, which are expected to be less susceptible to classical nuclear (torus) obscuration. Here, we seek to formalize this subpopulation of AGN with a prototypical candidate, SDSS J075139.06+402810.9. This shows infrared (IR) colours typical for AGN, an optical spectrum dominated by an early type galaxy continuum, an [O  iii ] λ5007Å limiting flux about two dex below Type 2 quasars at similar IR power, and a k -corrected 12  |$\mu$| m quasar-like luminosity of ∼ 1045 erg s−1. These characteristics are not consistent with jet and host galaxy dilution. A potential scenario to explain this AGN quiescence in the optical is a sky-covering 'cocoon' of obscuring material, such that the AGN ionizing radiation is unable to escape and excite gas on kpc scales. Alternatively, we may be witnessing the short phase between recent triggering of obscured AGN activity and the subsequent narrow-line excitation. This prototype could define the base properties of an emerging candidate AGN subtype – an intriguing transitional phase in AGN and galaxy evolution. [ABSTRACT FROM AUTHOR]

We have discovered an overdensity of Hα-emitting galaxies associated with a Planck compact source in the COSMOS field (PHz G237.0+42.5) through narrow-band imaging observations with the Subaru Multi-Object InfraRed Camera and Spectrograph (MOIRCS). This Planck -selected dusty proto-cluster at z = 2.16 has 38 Hα emitters including six spectroscopically confirmed galaxies in the observed MOIRCS 4 × 7 arcmin2 field (corresponding to ∼2.0 × 3.5 Mpc2 in the physical scale). We find that massive Hα emitters with log (M ⋆/M⊙) >10.5 are strongly clustered in the core of the proto-cluster (within ∼300 kpc from the density peak of the Hα emitters). Most of the Hα emitters in this proto-cluster lie along the star-forming main sequence using Hα-based estimates of the star formation rate (SFR). Meanwhile, the cluster total SFRs derived by integrating the Hα-based SFRs is an order of magnitude smaller than those estimated from Planck/Herschel far-infrared photometry. Our results suggest that Hα is a good observable for detecting moderately star-forming galaxies and for tracing the large-scale environment in and around high-redshift dusty proto-clusters. However, there is a possibility that a large fraction of star formation could be obscured by dust and undetected in Hα observations. [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 levels of heavy elements in stars are the product of enhancement by previous stellar generations, and the distribution of this metallicity among the population contains clues to the process by which a galaxy formed. Most famously, the 'G-dwarf problem' highlighted the small number of low-metallicity G-dwarf stars in the Milky Way, which is inconsistent with the simplest picture of a galaxy formed from a 'closed box' of gas. It can be resolved by treating the Galaxy as an open system that accretes gas throughout its life. This observation has classically only been made in the Milky Way, but the availability of high-quality spectral data from SDSS-IV MaNGA and the development of new analysis techniques mean that we can now make equivalent measurements for a large sample of spiral galaxies. Our analysis shows that high-mass spirals generically show a similar deficit of low-metallicity stars, implying that the Milky Way's history of gas accretion is common. By contrast, low-mass spirals show little sign of a G-dwarf problem, presenting the metallicity distribution that would be expected if such systems evolved as pretty much closed boxes. This distinction can be understood from the differing timescales for star formation in galaxies of differing masses. [ABSTRACT FROM AUTHOR]

The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) recently reported evidence for the presence of a common stochastic signal across their array of pulsars. The origin of this signal is still unclear. One possibility is that it is due to a stochastic gravitational-wave background (SGWB) in the ∼1–10 nHz frequency region. Taking the NANOGrav observational result at face value, we show that this signal would be fully consistent with an SGWB produced by an unresolved population of in-spiralling massive black hole binaries (MBHBs) predicted by current theoretical models. Considering an astrophysically agnostic model, the MBHB merger rate is loosely constrained. Including additional constraints from galaxy pairing fraction and MBH–bulge scaling relations, we find that the MBHB merger rate is |${1.2\times 10^{-5}}{\rm -}{4.5\times 10^{-4}}\, \mathrm{Mpc}^{-3}\, \mathrm{Gyr}^{-1}$| , the MBHB merger time-scale is |$\le 2.7\, \mathrm{Gyr}$|⁠ , and the norm of the M BH− M bulge relation is |$\ge 1.2\times 10^{8}\, {\rm M}_\odot$| (all quoted at 90 per  cent credible intervals). Regardless of the astrophysical details of MBHB assembly, the NANOGrav result would imply that a sufficiently large population of massive black holes pair up, form binaries and merge within a Hubble time. [ABSTRACT FROM AUTHOR]

In order to investigate the role of gas in the demise of star formation on kpc-scales, we compare the resolved molecular gas main sequence (rMGMS: |$\Sigma _{\rm H_2}$| versus Σ⋆) of star-forming regions to the sequence of 'retired' regions that have ceased to form new stars. Using data from the ALMaQUEST survey, we find that retired spaxels form a rMGMS that is distinct from that of star-forming spaxels, offset to lower |$\Sigma _{\rm H_2}$| at fixed Σ⋆ by a factor of ∼5. We study the rMGMS of star-forming and retired spaxels on a galaxy-by-galaxy basis for eight individual ALMaQUEST(ALMA MaNGA QUEnching and STar formation) galaxies. Six of these galaxies have their retired spaxels concentrated within the central few kpc. Molecular gas is detected in 40 – 100 per cent of retired spaxels in the eight galaxies in our sample. Both the star-forming and retired rMGMS show a diversity in normalization from galaxy to galaxy. However, in any given galaxy, the rMGMS for retired regions is found to be distinct from the star-forming sequence and gas fractions of retired spaxels are up to an order of magnitude lower than the star-forming spaxels. We conclude that quenching is associated with a depletion (but not absence) of molecular gas via a mechanism that typically begins in the centre of the galaxy. [ABSTRACT FROM AUTHOR]

It remains an open question as to how long ago the morphology that we see in a present-day galaxy was typically imprinted. Studies of galaxy populations at different redshifts reveal that the balance of morphologies has changed over time, but such snapshots cannot uncover the typical time-scales over which individual galaxies undergo morphological transformation, nor which are the progenitors of today's galaxies of different types. However, these studies also show a strong link between morphology and star formation rate (SFR) over a large range in redshift, which offers an alternative probe of morphological transformation. We therefore derive the evolution in SFR and stellar mass of a sample of 4342 galaxies in the SDSS-IV MaNGA survey through a stellar population 'fossil record' approach, and show that the average evolution of the population shows good agreement with known behaviour from previous studies. Although the correlation between a galaxy's contemporaneous morphology and SFR is strong over a large range of lookback times, we find that a galaxy's present-day morphology only correlates with its relatively recent (⁠|$\sim \! 2\, \textrm {Gyr}$|⁠) star formation history. We therefore find strong evidence that morphological transitions to galaxies' current appearance occurred on time-scales as short as a few billion years. [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]

In the (λR, ε) and (V /σ, ε) 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 β to the range allowed by physical solutions. We find that all four mock samples naturally predict the observed galaxy distribution on the (λR, ε) and (V /σ, ε) 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 (λR, ε) and (V /σ, ε) diagrams, are due to the lack of physical axisymmetric equilibrium solutions at high β anisotropy when the velocity ellipsoid is close to oblate. [ABSTRACT FROM AUTHOR]

Red and blue galaxies are traditionally classified using some specific cuts in colour or other galaxy properties, which are supported by empirical arguments. The vagueness associated with such cuts are likely to introduce a significant contamination in these samples. Fuzzy sets are vague boundary sets that can efficiently capture the classification uncertainty in the absence of any precise boundary. We propose a method for classification of galaxies according to their colours using fuzzy set theory. We use data from the Sloan Digital Sky Survey (SDSS) to construct a fuzzy set for red galaxies with its members having different degrees of 'redness'. We show that the fuzzy sets for the blue and green galaxies can be obtained from it using different fuzzy operations. We also explore the possibility of using fuzzy relation to study the relationship between different galaxy properties and discuss its strengths and limitations. [ABSTRACT FROM AUTHOR]

It has been established for decades that rotation curves deviate from the Newtonian gravity expectation given baryons alone below a characteristic acceleration scale |$g_{\dagger }\sim 10^{-8}\, \rm {cm\, s^{-2}}$|⁠ , a scale promoted to a new fundamental constant in MOND. In recent years, theoretical and observational studies have shown that the star formation efficiency (SFE) of dense gas scales with surface density, SFE ∼ Σ/Σcrit with |$\Sigma _{\rm crit} \sim \langle \dot{p}/m_{\ast }\rangle /(\pi \, G)\sim 1000\, \rm {M_{\odot }\, pc^{-2}}$| (where |$\langle \dot{p}/m_{\ast }\rangle$| is the momentum flux output by stellar feedback per unit stellar mass in a young stellar population). We argue that the SFE, more generally, should scale with the local gravitational acceleration, i.e. that SFE |${\sim}g_{\rm tot}/g_{\rm crit}\equiv (G\, M_{\rm tot}/R^{2}) / \langle \dot{p}/m_{\ast }\rangle$|⁠ , where M tot is the total gravitating mass and |$g_{\rm crit}=\langle \dot{p}/m_{\ast }\rangle = \pi \, G\, \Sigma _{\rm crit} \approx 10^{-8}\, \rm {cm\, s^{-2}} \approx \mathit{ g}_{\dagger }$|⁠. Hence, the observed g † may correspond to the characteristic acceleration scale above which stellar feedback cannot prevent efficient star formation, and baryons will eventually come to dominate. We further show how this may give rise to the observed acceleration scaling |$g_{\rm obs}\sim (g_{\rm baryon}\, g_{\dagger })^{1/2}$| (where g baryon is the acceleration due to baryons alone) and flat rotation curves. The derived characteristic acceleration g † can be expressed in terms of fundamental constants (gravitational constant, proton mass, and Thomson cross-section): |$g_{\dagger }\sim 0.1\, G\, m_{\mathrm{ p}}/\sigma _{\rm T}$|⁠. [ABSTRACT FROM AUTHOR]

Quenched massive spiral galaxies have attracted great attention recently, as more data are available to constrain their environment and cold gas content. However, the quenching mechanism is still uncertain, as it depends on the mass range and baryon budget of the galaxy. In this letter, we report the identification of a rare population of very massive, quenched spiral galaxies with stellar mass ≳1011 M⊙ and halo mass ≳1013 M⊙ from the Sloan Digital Sky Survey at redshift z ∼ 0.1. Our CO observations using the IRAM (Institute for Radio Astronomy in the Millimeter Range) 30-m telescope show that these galaxies contain only a small amount of molecular gas. Similar galaxies are also seen in the state-of-the-art semi-analytical models and hydrodynamical simulations. It is found from these theoretical models that these quenched spiral galaxies harbour massive black holes, suggesting that feedback from the central black holes has quenched these spiral galaxies. This quenching mechanism seems to challenge the popular scenario of the co-evolution between massive black holes and massive bulges. [ABSTRACT FROM AUTHOR]

The metallicity of star-forming gas in galaxies from the eagle (Evolution and Assembly of GaLaxies and their Environments) simulations increases with stellar mass. Here, we investigate whether the scatter around this relation correlates with morphology and/or stellar kinematics. At redshift z = 0, galaxies with more rotational support have lower metallicities on average when the stellar mass is below M ⋆ ≈ 1010 M⊙. This trend inverts at higher values of M ⋆, when prolate galaxies show typically lower metallicity. At increasing redshifts, the trend between rotational support and metallicity becomes weaker at low stellar mass but more pronounced at high stellar mass. We argue that the secondary dependence of metallicity on stellar kinematics is another manifestation of the observed anticorrelation between metallicity and star formation rate at a given stellar mass. At low masses, such trends seem to be driven by the different star formation histories of galaxies and stellar feedback. At high masses, feedback from active galactic nuclei and galaxy mergers plays a dominant role. [ABSTRACT FROM AUTHOR]

We investigate the relationship between the optical variability of galaxies and their distances from the centre of the Virgo cluster using Palomar Transient Factory data. We define the ratio between the standard deviation of the galaxy brightness and the mean value of the standard deviation as a measure of a galaxy's optical variability. A sample of 814 Virgo galaxies with 230 263 observations shows a monotonically decreasing trend of optical variability with increasing clustercentric distance. The variability level inside the cluster is 3.2σ higher than the level outside. We fit the variability with a linear function and find that the data reject a distance-independent model. We examine 217 background galaxies for comparison and find no significant trend in galaxy variability. We assess the relation with Monte Carlo simulation by rebuilding the brightness of each galaxy. The simulation shows a monotonically decreasing relation for member galaxy variability and a distance-independent relation for background galaxies. Our result is consistent with the theory that the cold gas flowing inwards the cluster centre fuels AGN activity. This work is a new implementation of the method using optical variability to investigate the relation between galaxies evolution and their environment. [ABSTRACT FROM AUTHOR]