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Galaxy environment plays an important role in driving the transformation of galaxies from blue and star forming to red and quenched. Recent works have focused on the role of cosmic web filaments in galaxy evolution and have suggested that stellar mass segregation, quenching of star formation, and gas-stripping may occur within filaments. We study the relationship between distance to filament and the stellar mass, colour, and H i gas content of galaxies using data from the REsolved Spectroscopy of a Local VolumE survey and Environmental COntext (ECO) catalogue, two overlapping census-style, volume-complete surveys. We use the Discrete Persistence Structures Extractor to identify cosmic web filaments over the full ECO area. We find that galaxies close to filaments have higher stellar masses, in agreement with previous results. Controlling for stellar mass, we find that galaxies also have redder colours and are more gas poor closer to filaments. When accounting for group membership and halo mass, we find that these trends in colour and gas content are dominated by the increasing prevalence of galaxy group environments close to filaments, particularly for high-halo mass and low-stellar mass galaxies. Filaments have an additional small effect on the gas content of galaxies in low-mass haloes, possibly due to cosmic web stripping. [ABSTRACT FROM AUTHOR]

Red geysers are a specific type of quiescent galaxy, denoted by twin jets emerging from their galactic centres. These bisymmetric jets possibly inject energy and heat into the surrounding material, effectively suppressing star formation by stabilizing cool gas. In order to confirm the presence and evolutionary consequences of these jets, this paper discusses the scaling, stacking, and conversion of 21-cm H  i flux data sourced from the H  i -MaNGA survey into H  i gas-to-stellar mass (G/S) spectra. Our samples were dominated by non-detections, or galaxies with weak H  i signals, and consequently by H  i upper limits. The stacking technique discussed successfully resolved emission features in both the red geyser G/S spectrum and the control sample G/S spectrum. From these stacked spectra, we find that on average, red geyser galaxies have G/S of 0.086 ± 0.011 (random) + 0.029 (systematic), while non-red geyser galaxies of similar stellar mass have a G/S ratio of 0.039 ± 0.018 (random) + 0.013 (systematic). Therefore, we find no statistically significant evidence that the H  i content of red geysers is different from the general quiescent population. [ABSTRACT FROM AUTHOR]

We have used Galaxy Zoo DECaLS (GZD) to study strong and weak bars in disc galaxies. Out of the 314 000 galaxies in GZD, we created a volume-limited sample (0.01 < z < 0.05, M r < − 18.96) which contains 1867 galaxies with reliable volunteer bar classifications in the ALFALFA footprint. In keeping with previous Galaxy Zoo surveys (such as GZ2), the morphological classifications from GZD agree well with previous morphological surveys. GZD considers galaxies to either have a strong bar (15.5 per cent), a weak bar (28.1 per cent) or no bar (56.4 per cent), based on volunteer classifications on images obtained from the DECaLS survey. This places GZD in a unique position to assess differences between strong and weak bars. We find that the strong bar fraction is typically higher in quiescent galaxies than in star-forming galaxies, while the weak bar fraction is similar. Moreover, we have found that strong bars facilitate the quenching process in star-forming galaxies, finding higher fibre star formation rates (SFRs), lower gas masses, and shorter depletion time-scales in these galaxies compared to unbarred galaxies. However, we also found that any differences between strong and weak bars disappear when controlling for bar length. Based on this, we conclude that weak and strong bars are not fundamentally different phenomena. Instead, we propose that there is a continuum of bar types, which varies from 'weakest' to 'strongest'. [ABSTRACT FROM AUTHOR]

We measure the environmental dependence, where environment is defined by the distance to the third nearest neighbor, of multiple galaxy properties inside the Environmental COntext (ECO) catalog. We focus primarily on void galaxies, which we define as the 10% of galaxies having the lowest local density. We compare the properties of void and non-void galaxies: baryonic mass, color, fractional stellar mass growth rate (FSMGR), morphology, and gas-to-stellar-mass ratio (estimated from a combination of H i data and photometric gas fractions calibrated with the REsolved Spectroscopy Of a Local VolumE survey). Our void galaxies typically have lower baryonic masses than galaxies in denser environments, and they display the properties expected of a lower mass population: they have more late types, are bluer, have a higher FSMGR, and are more gas-rich. We control for baryonic mass and investigate the extent to which void galaxies are different at fixed mass. Void galaxies are bluer, more gas-rich, and more star-forming at fixed mass than non-void galaxies, which is a possible signature of galaxy assembly bias. Furthermore, we show that these trends persist even at fixed mass and morphology, and we find that voids host a distinct population of early types that are bluer and more star-forming than the typical red and quenched early types. In addition to these empirical observational results, we also present theoretical results from mock catalogs with built-in galaxy assembly bias. We show that a simple matching of galaxy properties to (sub)halo properties, such as mass and age, can recover the observed environmental trends in ECO galaxies. [ABSTRACT FROM AUTHOR]

We study the faint stellar halo of isolated central galaxies, by stacking galaxy images in the HSC survey and accounting for the residual sky background sampled with random points. The surface brightness profiles in HSC r band are measured for a wide range of galaxy stellar masses (9.2 < log10 M ∗/M⊙ < 11.4) and out to 120 kpc. Failing to account for the stellar halo below the noise level of individual images will lead to underestimates of the total luminosity by ≤15%. Splitting galaxies according to the concentration parameter of their light distributions, we find that the surface brightness profiles of low-concentration galaxies drop faster between 20 and 100 kpc than those of high-concentration galaxies. Albeit the large galaxy-to-galaxy scatter, we find a strong self-similarity of the stellar halo profiles. They show unified forms once the projected distance is scaled by the halo virial radius. The colour of galaxies is redder in the centre and bluer outside, with high-concentration galaxies having redder and more flattened colour profiles. There are indications of a colour minimum, beyond which the colour of the outer stellar halo turns red again. This colour minimum, however, is very sensitive to the completeness in masking satellite galaxies. We also examine the effect of the extended PSF in the measurement of the stellar halo, which is particularly important for low-mass or low-concentration galaxies. The PSF-corrected surface brightness profile can be measured down to ∼31  |$\mathrm{mag}\, \mathrm{arcsec}^{-2}$| at 3σ significance. PSF also slightly flattens the measured colour profiles. [ABSTRACT FROM AUTHOR]

We show how the Radon transform (defined as a series of line integrals through an image at different orientations and offsets from the origin) can be used as a simple, non-parametric tool to characterize galaxy velocity fields, specifically their global kinematic position angles (PA k ) and any radial variation or asymmetry in PA k . This method is fast and easily automated, making it particularly beneficial in an era where integral field unit (IFU) and interferometric surveys are yielding samples of thousands of galaxies. We demonstrate the Radon transform by applying it to gas and stellar velocity fields from the first ∼2800 galaxies of the SDSS-IV MaNGA IFU survey. We separately classify gas and stellar velocity fields into five categories based on the shape of their radial PA k profiles. At least half of stellar velocity fields and two-thirds of gas velocity fields are found to show detectable deviations from uniform coplanar circular motion, although most of these variations are symmetric about the centre of the galaxy. The behaviour of gas and stellar velocity fields is largely independent, even when PA k profiles for both components are measured over the same radii. We present evidence that one class of symmetric PA k variations is likely associated with bars and/or oval distortions, while another class is more consistent with warped discs. This analysis sets the stage for more in-depth future studies which explore the origin of diverse kinematic behaviour in the galaxy population. [ABSTRACT FROM AUTHOR]

Regions of disc galaxies with widespread star formation tend to be both gravitationally unstable and self-shielded against ionizing radiation, whereas extended outer discs with little or no star formation tend to be stable and unshielded on average. We explore what drives the transition between these two regimes, specifically whether discs first meet the conditions for selfshielding (parametrized by dust optical depth, τ ) or gravitational instability (parametrized by a modified version of Toomre's instability parameters, Qthermal, which quantifies the stability of a gas disc that is thermally supported at T = 104 K).We first introduce a new metric formed by the product of these quantities, Qthermalτ , which indicates whether the conditions for disc instability or self-shielding are easier to meet in a given region of a galaxy, and we discuss how Qthermalτ can be constrained even in the absence of direct gas information. We then analyse a sample of 13 galaxies with resolved gas measurements and find that on average galaxies will reach the threshold for disc instabilities (Qthermal < 1) before reaching the threshold for self-shielding (τ > 1). Using integral field spectroscopic observations of a sample of 236 galaxies from the Mapping Nearby Galaxies at APO (MaNGA) survey, we find that the value of Qthermalτ in star-forming discs is consistent with similar behaviour. These results support a scenario where disc fragmentation and collapse occurs before self-shielding, suggesting that gravitational instabilities are the primary condition for widespread star formation in galaxy discs. Our results support similar conclusions based on recent galaxy simulations. [ABSTRACT FROM AUTHOR]

Motivated by the idea that a subset of high-velocity clouds (HVCs) trace dark matter substructure in the Local Group, we search for signs of star formation in the Smith Cloud, a nearby ∼2 × 106M☉ HVC currently falling into the Milky Way. Using GALEX NUV and WISE/2MASS NIR photometry, we apply a series of colour and apparent magnitude cuts to isolate candidate O and B stars that are plausibly associated with the Smith Cloud. We find an excess of stars along the line of sight to the cloud, but not at a statistically significant level relative to a control region. The number of stars found in projection on the cloud after removing an estimate of the contamination by the Milky Way implies an average star formation rate surface density of 10-4.8±0.3 M☉ yr-1 kpc-2, assuming the cloud has been forming stars at a constant rate since its first passage through the Milky Way ∼70 Myr ago. This value is consistent with the star formation rate expected based on the average gas density of the cloud. We also discuss how the newly discovered star-forming galaxy Leo P has very similar properties to the Smith Cloud, but its young stellar population would not have been detected at a statistically significant level using our method. Thus, we cannot yet rule out the idea that the Smith Cloud is really a dwarf galaxy. [ABSTRACT FROM AUTHOR]

We relate transitions in galaxy structure and gas content to refueling, here defined to include both the external gas accretion and the internal gas processing needed to renew reservoirs for star formation. We analyze two z = 0 data sets: a high-quality ∼200 galaxy sample (the Nearby Field Galaxy Survey, data release herein) and a volume-limited ∼3000 galaxy sample with reprocessed archival data. Both reach down to baryonic masses ∼109M☼ and span void-to-cluster environments. Two mass-dependent transitions are evident: (1) below the “gas-richness threshold” scale (V ∼ 125 km s–1), gas-dominated quasi-bulgeless Sd-Im galaxies become numerically dominant; while (2) above the “bimodality” scale (V ∼ 200 km s–1), gas-starved E/S0s become the norm. Notwithstanding these transitions, galaxy mass (or V as its proxy) is a poor predictor of gas-to-stellar mass ratio Mgas/M*. Instead, Mgas/M* correlates well with the ratio of a galaxy's stellar mass formed in the last Gyr to its preexisting stellar mass, such that the two ratios have numerically similar values. This striking correspondence between past-averaged star formation and current gas richness implies routine refueling of star-forming galaxies on Gyr timescales. We argue that this refueling underlies the tight Mgas/M* versus color correlations often used to measure “photometric gas fractions.” Furthermore, the threshold and bimodality scale transitions reflect mass-dependent demographic shifts between three refueling regimes—accretion-dominated, processing-dominated, and quenched. In this picture, gas-dominated dwarfs are explained not by inefficient star formation but by overwhelming gas accretion, which fuels stellar mass doubling in ≲1 Gyr. Moreover, moderately gas-rich bulged disks such as the Milky Way are transitional, becoming abundant only in the narrow range between the threshold and bimodality scales. [ABSTRACT FROM AUTHOR]

To assess how external factors such as local interactions and fresh gas accretion influence the global interstellar medium of galaxies, we analyze the relationship between recent enhancements of central star formation and total molecular-to-atomic (H2/HI) gas ratios, using a broad sample of field galaxies spanning early-to-late type morphologies, stellar masses of 107.2–1011.2M⊙, and diverse stages of evolution. We find that galaxies occupy several loci in a “fueling diagram” that plots H2/HI ratio versus mass-corrected blue-centeredness, a metric tracing the degree to which galaxies have bluer centers than the average galaxy at their stellar mass. Spiral galaxies of all stellar masses show a positive correlation between H2/HI ratio and mass-corrected blue-centeredness. When combined with previous results linking mass-corrected blue-centeredness to external perturbations, this correlation suggests a systematic link between local galaxy interactions and molecular gas inflow/replenishment. Intriguingly, E/S0 galaxies show a more complex picture: some follow the same correlation, some are quenched, and a distinct population of blue-sequence E/S0 galaxies (with masses below key scales associated with transitions in gas richness) defines a separate loop in the fueling diagram. This population appears to be composed of low-mass merger remnants currently in late- or post-starburst states, in which the burst first consumes the H2 while the galaxy center keeps getting bluer, then exhausts the H2, at which point the burst population reddens as it ages. Multiple lines of evidence suggest connected evolutionary sequences in the fueling diagram. In particular, tracking total gas-to-stellar mass ratios within the fueling diagram provides evidence of fresh gas accretion onto low-mass E/S0s emerging from their central starburst episodes. Drawing on a comprehensive literature search, we suggest that virtually all galaxies follow the same evolutionary patterns found in our broad sample. [ABSTRACT FROM AUTHOR]

7 NNdist proj Distance to nearest neighbor (Mpc) calculated as the projected distance to the nearest neighbor in a cylindrical volume within cz = 500kms -1 of the main object. Callie E. Hood 1, Sheila J. Kannappan 1, David V. Stark 1,2, Ian P. Dell'Antonio 3, Amanda J. Moffett 1,4, Kathleen D. Eckert 1,5, Mark A. Norris 6, and David Hendel 7 1 Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27516, USA 2 KavliInstitute forthePhysicsand MathematicsoftheUniverse (WPI),TheUniversity ofTokyo InstitutesforAdvancedStudy,TheUniversityofTokyo,Kashiwa, Chiba 277-8583, Japan 3 Department of Physics, Brown University, Box 1843, Providence, RI 02912, USA 4 Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37240, USA 5 Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104, USA 6 Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE, UK 7 Department of Astronomy, Columbia University, 550 W 120th Street, New York, NY 10027, USA Received 2020 December 17; revised 2021 March 2; published 2021 April 7 Supporting material: machine-readable table Table 2 in the published article provided incorrect kd-tree nearest neighbor distances calculated using the kd-tree algorithm for all galaxies. The corrected Table 2 in this erratum provides updated kd-tree and projected nearest neighbor distances correctedfortheaforementionederrorsandomittingrs1492,andtheupdatedvaluesdonotchangeanyoftheresultsinthepublished article. [Extracted from the article]