arXiv subjects

Michael Balogh

Publications and source records attributed to Michael Balogh.

At least 37 records · Page 2Linked to original sources

arXiv2018

HST/WFC3 grism observations of $z~\mathtt{\sim}~1$ clusters: The cluster vs. field stellar mass-size relation and evidence for size growth of quiescent galaxies from minor mergers

Minor mergers are thought to be responsible for the size growth of quiescent field galaxies with decreasing redshift. We test this hypothesis using the cluster environment as a laboratory. Satellite galaxies in clusters move at high velocities, making mergers between them rare. The stellar mass-size relation in ten clusters and in the field is measured and compared at $z~\mathtt{\sim}~1$. Our cluster sample contains 344 spectroscopically-confirmed cluster members with Gemini/GMOS and 182 confirmed with HST WFC3 G141 grism spectroscopy. On average, quiescent and star-forming cluster galaxies are smaller than their field counterparts by ($0.08\pm0.04$) dex and ($0.07\pm0.01$) dex respectively. These size offsets are consistent with the average sizes of quiescent and star-forming field galaxies between $1.2\leqslant z\leqslant1.5$, implying the cluster environment has inhibited size growth between this period and $z~\mathtt{\sim}~1$. The negligible differences measured between the $z~\mathtt{\sim}~0$ field and cluster quiescent mass-size relations in other works imply that the average size of quiescent cluster galaxies must rise with decreasing redshift. Using a toy model, we show that the disappearance of the compact cluster galaxies might be explained if, on average, $\mathtt{\sim}40\%$ of them merge with their brightest cluster galaxies (BCGs) and $\mathtt{\sim}60\%$ are tidally destroyed into the intra-cluster light (ICL) between $0\leqslant z\leqslant1$. This is in agreement with the observed stellar mass growth of BCGs between $0\leqslant z\leqslant1$ and the observed ICL stellar mass fraction at $z~\mathtt{\sim}~0$. Our results support minor mergers as the cause for the size growth in quiescent field galaxies, with cluster-specific processes responsible for the similarity between the field and cluster quiescent mass-size relations at low redshift.

astro-ph.GA↗

arXiv2018

Chandra centres for COSMOS X-ray galaxy groups: Differences in stellar properties between central dominant and offset brightest group galaxies

We present the results of a search for galaxy clusters and groups in the $\sim2$ square degree of the COSMOS field using all available X-ray observations from the XMM-Newton and Chandra observatories. We reach an X-ray flux limit of $3\times10^{-16}\;ergs\;cm^{-2}\;s^{-1}$ in 0.5--2 keV range, and identify 247 X-ray groups with $M_{200c}=8\times10^{12}-3\times10^{14}\;M_{\odot}$ at a redshift range of $0.08\leq z<1.53$, using the multiband photometric redshift and the master spectroscopic redshift catalogues of the COSMOS. The X-ray centres of groups are determined using high-resolution Chandra imaging. We investigate the relations between the offset of the brightest group galaxies (BGGs) from halo X-ray centre and group properties and compare with predictions from semi-analytic models and hydrodynamical simulations. We find that BGG offset decreases with both increasing halo mass and decreasing redshift with no strong dependence on the X-ray flux and SNR. We show that the BGG offset decreases as a function of increasing magnitude gap with no considerable redshift dependent trend. The stellar mass of BGGs in observations extends over a wider dynamic range compared to model predictions. At $z<0.5$, the central dominant BGGs become more massive than those with large offsets by up to 0.3dex, in agreement with model prediction. The observed and predicted lognormal scatter in the stellar mass of both low- and large-offset BGGs at fixed halo mass is $\sim0.3$dex.

astro-ph.GA↗

arXiv2018

The Local Cluster Survey I: Evidence of Outside-In Quenching in Dense Environments

The goal of the Local Cluster Survey is to look for evidence of environmentally driven quenching among star-forming galaxies in nearby galaxy groups and clusters. Quenching is linked with environment and stellar mass, and much of the current observational evidence comes from the integrated properties of galaxies. However, the relative size of the stellar and star-forming disk is sensitive to environmental processing and can help identify the mechanisms that lead to a large fraction of quenched galaxies in dense environments. Toward this end, we measure the size of the star-forming disks for 224 galaxies in nine groups and clusters (0.02 0.1 M$_\odot$/yr) using 24um imaging from the Spitzer Space Telescope. We normalize the 24um effective radius (R24) by the size of the stellar disk (Rd). We find that star-forming galaxies with higher bulge-to-total ratios (B/T) and galaxies in more dense environments have more centrally concentrated star formation. Comparison with H~I mass fractions and NUV-r colors indicates that a galaxy's transition from gas-rich and blue to depleted and red is accompanied by an increase in the central concentration of star formation. We build a simple model to constrain the timescale over which the star-forming disks shrink in the cluster environment. Our results are consistent with a long-timescale (>2Gyr) mechanism that produces outside-in quenching, such as the removal of the extended gas halo or weak stripping of the cold disk gas.

astro-ph.GA↗

arXiv2016

The Detailed Science Case for the Maunakea Spectroscopic Explorer: the Composition and Dynamics of the Faint Universe

MSE is an 11.25m aperture observatory with a 1.5 square degree field of view that will be fully dedicated to multi-object spectroscopy. More than 3200 fibres will feed spectrographs operating at low (R ~ 2000 - 3500) and moderate (R ~ 6000) spectral resolution, and approximately 1000 fibers will feed spectrographs operating at high (R ~ 40000) resolution. MSE is designed to enable transformational science in areas as diverse as tomographic mapping of the interstellar and intergalactic media; the in-situ chemical tagging of thick disk and halo stars; connecting galaxies to their large scale structure; measuring the mass functions of cold dark matter sub-halos in galaxy and cluster-scale hosts; reverberation mapping of supermassive black holes in quasars; next generation cosmological surveys using redshift space distortions and peculiar velocities. MSE is an essential follow-up facility to current and next generations of multi-wavelength imaging surveys, including LSST, Gaia, Euclid, WFIRST, PLATO, and the SKA, and is designed to complement and go beyond the science goals of other planned and current spectroscopic capabilities like VISTA/4MOST, WHT/WEAVE, AAT/HERMES and Subaru/PFS. It is an ideal feeder facility for E-ELT, TMT and GMT, and provides the missing link between wide field imaging and small field precision astronomy. MSE is optimized for high throughput, high signal-to-noise observations of the faintest sources in the Universe with high quality calibration and stability being ensured through the dedicated operational mode of the observatory. (abridged)

astro-ph.IM↗

arXiv2016

A concise overview of the Maunakea Spectroscopic Explorer

This short document is intended as a companion and introduction to the Detailed Science Case (DSC) for the Maunakea Spectroscopic Explorer. It provides a concise summary of the essential characteristics of MSE from the perspective of the international astronomical community. MSE is a wide field telescope (1.5 square degree field of view) with an aperture of 11.25m. It is dedicated to multi-object spectroscopy at several different spectral resolutions in the range R ~ 2500 - 40000 over a broad wavelength range (0.36 - 1.8μm). MSE will enable transformational science in areas as diverse as exoplanetary host characterization; stellar monitoring campaigns; tomographic mapping of the interstellar and intergalactic media; the in-situ chemical tagging of the distant Galaxy; connecting galaxies to the large scale structure of the Universe; measuring the mass functions of cold dark matter sub-halos in galaxy and cluster-scale hosts; reverberation mapping of supermassive black holes in quasars. MSE is the largest ground based optical and near infrared telescope in its class, and it will occupy a unique and critical role in the emerging network of astronomical facilities active in the 2020s. MSE is an essential follow-up facility to current and next generations of multi-wavelength imaging surveys, including LSST, Gaia, Euclid, eROSITA, SKA, and WFIRST, and is an ideal feeder facility for E-ELT, TMT and GMT.

astro-ph.IM↗

arXiv2014

The connection between galaxy structure and quenching efficiency

Using data from the SDSS-DR7, including structural measurements from 2D surface brightness fits with GIM2D, we show how the fraction of quiescent galaxies depends on galaxy stellar mass $M_*$, effective radius $R_e$, fraction of $r-$band light in the bulge, $B/T$, and their status as a central or satellite galaxy at $0.01 0.3$ are excluded. For satellite galaxies, the quiescent fraction is always larger than that of central galaxies, for any combination of $M_*$, $R_e$ and $B/T$. The quenching efficiency is not constant, but reaches a maximum of $\sim 0.7$ for galaxies with $9 < \log(M_*/M_\odot) < 9.5$ and $R_e<1$ kpc. This is the same region of parameter space in which the satellite fraction itself reaches its maximum value, suggesting that the transformation from an active central galaxy to a quiescent satellite is associated with a reduction in $R_e$ due to an increase in dominance of a bulge component.

astro-ph.GA↗

arXiv2014

The Phase Space and Stellar Populations of Cluster Galaxies at z ~ 1: Simultaneous Constraints on the Location and Timescale of Satellite Quenching

We investigate the velocity vs. position phase space of z ~ 1 cluster galaxies using a set of 424 spectroscopic redshifts in 9 clusters drawn from the GCLASS survey. Dividing the galaxy population into three categories: quiescent, star-forming, and poststarburst, we find that these populations have distinct distributions in phase space. Most striking are the poststarburst galaxies, which are commonly found at small clustercentric radii with high clustercentric velocities, and appear to trace a coherent ``ring" in phase space. Using several zoom simulations of clusters we show that the coherent distribution of the poststarbursts can be reasonably well-reproduced using a simple quenching scenario. Specifically, the phase space is best reproduced if satellite quenching occurs on a rapid timescale (0.1 < tau_{Q} < 0.5 Gyr) after galaxies make their first passage of R ~ 0.5R_{200}, a process that takes a total time of ~ 1 Gyr after first infall. We compare this quenching timescale to the timescale implied by the stellar populations of the poststarburst galaxies and find that the poststarburst spectra are well-fit by a rapid quenching (tau_{Q} = 0.4^{+0.3}_{-0.4} Gyr) of a typical star-forming galaxy. The similarity between the quenching timescales derived from these independent indicators is a strong consistency check of the quenching model. Given that the model implies satellite quenching is rapid, and occurs well within R_{200}, this would suggest that ram-pressure stripping of either the hot or cold gas component of galaxies are the most plausible candidates for the physical mechanism. The high cold gas consumption rates at z ~ 1 make it difficult to determine if hot or cold gas stripping is dominant; however, measurements of the redshift evolution of the satellite quenching timescale and location may be capable of distinguishing between the two.

astro-ph.GA↗

arXiv2013

Tully-Fisher analysis of the multiple cluster system Abell 901/902

We derive rotation curves from optical emission lines of 182 disk galaxies (96 in the cluster and 86 in the field) in the region of Abell 901/902 located at $z\sim 0.165$. We focus on the analysis of B-band and stellar-mass Tully-Fisher relations. We examine possible environmental dependencies and differences between normal spirals and "dusty red" galaxies, i.e. disk galaxies that have red colors due to relatively low star formation rates. We find no significant differences between the best-fit TF slope of cluster and field galaxies. At fixed slope, the field population with high-quality rotation curves (57 objects) is brighter by $ΔM_{B}=-0\fm42\pm0\fm15$ than the cluster population (55 objects). We show that this slight difference is at least in part an environmental effect. The scatter of the cluster TFR increases for galaxies closer to the core region, also indicating an environmental effect. Interestingly, dusty red galaxies become fainter towards the core at given rotation velocity (i.e. total mass). This indicates that the star formation in these galaxies is in the process of being quenched. The luminosities of normal spiral galaxies are slightly higher at fixed rotation velocity for smaller cluster-centric radii. Probably these galaxies are gas-rich (compared to the dusty red population) and the onset of ram-pressure stripping increases their star-formation rates. The results from the TF analysis are consistent with and complement our previous findings. Dusty red galaxies might be an intermediate stage in the transformation of infalling field spiral galaxies into cluster S0s, and this might explain the well-known increase of the S0 fraction in galaxy clusters with cosmic time.

astro-ph.CO↗

arXiv2013

Ram pressure and dusty red galaxies - key factors in the evolution of the multiple cluster system Abell 901/902

We present spectroscopic observations of 182 disk galaxies (96 in the cluster and 86 in the field environment) in the region of the Abell 901/902 multiple cluster system, which is located at a redshift of $z\sim 0.165$. The presence of substructures and non-Gaussian redshift distributions indicate that the cluster system is dynamically young and not in a virialized state. We find evidence for two important galaxy populations. \textit{Morphologically distorted galaxies} are probably subject to increased tidal interactions. They show pronounced rotation curve asymmetries at intermediate cluster-centric radii and low rest-frame peculiar velocities. \textit{Morphologically undistorted galaxies} show the strongest rotation curve asymmetries at high rest-frame velocities and low cluster-centric radii. Supposedly, this group is strongly affected by ram-pressure stripping due to interaction with the intra-cluster medium. Among the morphologically undistorted galaxies, dusty red galaxies have particularly strong rotation curve asymmetries, suggesting ram pressure is an important factor in these galaxies. Furthermore, dusty red galaxies on average have a bulge-to-total ratio higher by a factor of two than cluster blue cloud and field galaxies. The fraction of kinematically distorted galaxies is 75% higher in the cluster than in the field environment. This difference mainly stems from morphological undistorted galaxies, indicating a cluster-specific interaction process that only affects the gas kinematics but not the stellar morphology. Also the ratio between gas and stellar scale length is reduced for cluster galaxies compared to the field sample. Both findings could be best explained by ram-pressure effects.

astro-ph.CO↗

arXiv2012

AGN host galaxies at redshift z~0.7: peculiar or not?

We perform a quantitative morphological comparison between the hosts of Active Galactic Nuclei (AGN) and quiescent galaxies at intermediate redshifts (z~0.7). The imaging data are taken from the large HST/ACS mosaics of the GEMS and STAGES surveys. Our main aim is to test whether nuclear activity at this cosmic epoch is triggered by major mergers. Using images of quiescent galaxies and stars, we create synthetic AGN images to investigate the impact of an optical nucleus on the morphological analysis of AGN hosts. Galaxy morphologies are parameterized using the asymmetry index A, concentration index C, Gini coefficient G and M20 index. A sample of ~200 synthetic AGN is matched to 21 real AGN in terms of redshift, host brightness and host-to-nucleus ratio to ensure a reliable comparison between active and quiescent galaxies. The optical nuclei strongly affect the morphological parameters of the underlying host galaxy. Taking these effects into account, we find that the morphologies of the AGN hosts are clearly distinct from galaxies undergoing violent gravitational interactions. In fact, the host galaxies' distributions in morphological descriptor space are more similar to undisturbed galaxies than major mergers. Intermediate-luminosity (Lx < 10^44 erg/s) AGN hosts at z~0.7 show morphologies similar to the general population of massive galaxies with significant bulges at the same redshifts. If major mergers are the driver of nuclear activity at this epoch, the signatures of gravitational interactions fade rapidly before the optical AGN phase starts, making them undetectable on single-orbit HST images, at least with usual morphological descriptors. This could be investigated in future synthetic observations created from numerical simulations of galaxy-galaxy interactions.

astro-ph.CO↗

arXiv2011

The Gemini Cluster Astrophysics Spectroscopic Survey (GCLASS): The Role of Environment and Self-Regulation in Galaxy Evolution at z ~ 1

We evaluate the effects of environment and stellar mass on galaxy properties at 0.85 < z < 1.20 using a 3.6um-selected spectroscopic sample of 797 cluster and field galaxies drawn from the GCLASS survey. We confirm that for galaxies with LogM* > 9.3 the well-known correlations between environment and properties such as star-forming fraction (f_SF), SFR, SSFR, D(4000), and color are already in place at z ~ 1. We separate the effects of environment and stellar mass on galaxies by comparing the properties of star-forming and quiescent galaxies at fixed environment, and fixed stellar mass. The SSFR of star-forming galaxies at fixed environment is correlated with stellar mass; however, at fixed stellar mass it is independent of environment. The same trend exists for the D(4000) measures of both the star-forming and quiescent galaxies and shows that their properties are determined primarily by their stellar mass, not by their environment. Instead, it appears that environment's primary role is to control the fraction of star-forming galaxies. Using the spectra we identify candidate poststarburst galaxies and find that those with 9.3 < LogM* < 10.7 are 3.1 +/- 1.1 times more common in high-density regions compared to low-density regions. The clear association of poststarbursts with high-density regions as well as the lack of a correlation between the SSFRs and D(4000)s of star-forming galaxies with their environment suggests that at z ~ 1 the environmental-quenching timescale must be rapid. Lastly, we construct a simple quenching model which demonstrates that the lack of a correlation between the D(4000) of quiescent galaxies and their environment results naturally if self quenching dominates over environmental quenching at z > 1, or if the evolution of the self-quenching rate mirrors the evolution of the environmental-quenching rate at z > 1, regardless of which dominates.

astro-ph.CO↗

arXiv2011

From Star-Forming Spirals to Passive Spheroids: Integral Field Spectroscopy of E+A Galaxies

We present three dimensional spectroscopy of eleven E+A galaxies, selected for their strong H-delta absorption but weak (or non-existent) [OII]3727 and H-alpha emission. This selection suggests that a recent burst of star-formation was triggered but subsequently abruptly ended. We probe the spatial and spectral properties of both the young (~1Gyr) and old (few Gyr) stellar populations. Using the H-delta equivalent widths we estimate that the burst masses must have been at least 10% by mass (Mburst~10^10Mo), which is also consistent with the star-formation history inferred from the broad-band SEDs. On average the A-stars cover ~33% of the galaxy image, extending over 2-15kpc^2, indicating that the characteristic E+A signature is a property of the galaxy as a whole and not due to a heterogeneous mixture of populations. In approximately half of the sample, we find that the A-stars, nebular emission, and continuum emission are not co-located, suggesting that the newest stars are forming in a different place than those that formed ~1Gyr ago, and that recent star-formation has occurred in regions distinct from the oldest stellar populations. At least ten of the galaxies (91%) have dynamics that class them as "fast rotators" with magnitudes and dynamics comparable to local ellipticals and S0's. We also find a correlation between the spatial extent of the A-stars and dynamics such that the fastest rotators tend to have the most compact A-star populations, providing new constraints on models that aim to explain the transformation of later type galaxies into early types. Finally, we show that there are no obvious differences between the line extents and kinematics of E+A galaxies detected in the radio (AGN) compared to non-radio sources, suggesting that AGN feedback does not play a dramatic role in defining their properties, or that its effects are short.

astro-ph.CO↗

arXiv2011

CFHT Legacy Ultraviolet Extension (CLUE): Witnessing Galaxy Transformations up to 7 Mpc from Rich Cluster Cores

Using the optical data from the Wide component of the CFHT Legacy Survey, and new ultraviolet data from GALEX, we study the colours and specific star formation rates (SSFR) of ~100 galaxy clusters at 0.16 0.7 M_sun/yr at z~0.2 and SFR>1.2 M_sun/yr at z~0.3) have no measurable dependence on the cluster-centric radius, and are consistent with the field values. However, the fraction of galaxies with SFR above these thresholds, and the fraction of optically blue galaxies, are lower for the overdense galaxy population in the cluster outskirts compared with the average field value, at all stellar masses M*>10^{9.8} M_sun and at all radii out to at least 7Mpc. Most interestingly, the fraction of blue galaxies that are forming stars at a rate below our UV detection limit is much higher in all radial bins around our cluster sample, compared with the general field value. This is most noticeable for massive galaxies M*>10^{10.7} M_sun; while almost all blue field galaxies of this mass have detectable star formation, this is true for less than 20% of the blue cluster galaxies, even at 7Mpc from the cluster centre. Our results support a scenario where galaxies are pre-processed in locally overdense regions, in a way that reduces their SFR below our UV detection limit, but not to zero.

astro-ph.CO↗

arXiv2010

Dependence of Star Formation Activity On Stellar Mass and Environment From the Redshift One LDSS-3 Emission Line Survey (ROLES)

Using the sample from the \it Redshift One LDSS3 Emission line Survey \rm (ROLES), we probe the dependence of star formation rate (SFR) and specific star formation rate (sSFR) as a function of stellar mass $M_*$ and environment as defined by local galaxy density, in the CDFS field. Our spectroscopic sample consists of 312 galaxies with $K_{AB}<24$, corresponding to stellar mass $\log(M_*/M_{\sun})>8.5$, and with [OII] derived star-formation rates SFR$>0.3M_{\sun}/$yr, at $0.889\leq z \leq 1.149$. The results have been compared directly with the Sloan Digital Sky Survey Stripe 82 sample at $0.032\leq z \leq 0.05$. For star-forming galaxies, we confirm that there is little correlation between SFR and density at $z\sim 0$. However, for the lowest mass galaxies in our $z\sim 1$ sample, those with $\log(M_*/M_{\sun})<10$, we find that both the median SFR and specific SFR {\it increase} significantly with increasing local density. The "downsizing" trend for low mass galaxies to be quenched progressively later in time appears to be more pronounced in moderately overdense environments. Overall we find that the evolution of star-formation in galaxies is most strongly driven by their stellar mass, with local galaxy density playing a role that becomes increasingly important for lower mass galaxies.

astro-ph.CO↗

arXiv2009

Less than 10 percent of star formation in z=0.6 massive galaxies is triggered by major interactions

Both observations and simulations show that major tidal interactions or mergers between gas-rich galaxies can lead to intense bursts of starformation. Yet, the average enhancement in star formation rate (SFR) in major mergers and the contribution of such events to the cosmic SFR are not well estimated. Here we use photometric redshifts, stellar masses and UV SFRs from COMBO-17, 24 micron SFRs from Spitzer and morphologies from two deep HST cosmological survey fields (ECDFS/GEMS and A901/STAGES) to study the enhancement in SFR as a function of projected galaxy separation. We apply two-point projected correlation function techniques, which we augment with morphologically-selected very close pairs (separation <2 arcsec) and merger remnants from the HST imaging. Our analysis confirms that the most intensely star-forming systems are indeed interacting or merging. Yet, for massive (M* > 10^10 Msun) star-forming galaxies at 0.4<z<0.8, we find that the SFRs of galaxies undergoing a major interaction (mass ratios <1:4 and separations < 40 kpc) are only 1.80 +/- 0.30 times higher than the SFRs of non-interacting galaxies when averaged over all interactions and all stages of the interaction, in good agreement with other observational works. We demonstrate that these results imply that <10% of star formation at 0.4 < z < 0.8 is triggered directly by major mergers and interactions; these events are not important factors in the build-up of stellar mass since z=1.

astro-ph.CO↗

arXiv2009

Optically-passive spirals: The missing link in gradual star formation suppression upon cluster infall

Galaxies migrate from the blue cloud to the red sequence when their star formation is quenched. Here, we report on galaxies quenched by environmental effects and not by mergers or strong AGN as often invoked: They form stars at a reduced rate which is optically even less conspicuous, and manifest a transition population of blue spirals evolving into S0 galaxies. These 'optically passive' or 'red spirals' are found in large numbers in the STAGES project (and by Galaxy Zoo) in the infall region of clusters and groups.

astro-ph.CO↗

arXiv2009

A spectroscopic measure of the star-formation rate density in dwarf galaxies at z~1

We use a K-selected (22.5 < K_AB < 24.0) sample of dwarf galaxies (8.4 < log(M*/Msun) < 10) at 0.89<z<1.15 in the Chandra Deep Field South (CDFS) to measure their contribution to the global star-formation rate density (SFRD), as inferred from their [OII] flux. By comparing with [OII]-based studies of higher stellar mass galaxies, we robustly measure a turnover in the [OII] luminosity density at a stellar mass of M~10^10 Msun. By comparison with the [OII]-based SFRD measured from the Sloan Digital Sky Survey we confirm that, while the SFRD of the lowest-mass galaxies changes very little with time, the SFRD of more massive galaxies evolves strongly, such that they dominate the SFRD at z = 1.

astro-ph.CO↗

arXiv2008

The STAGES view of red spirals and dusty red galaxies: Mass-dependent quenching of star-formation in cluster infall

We investigate the properties of optically passive spirals and dusty red galaxies in the A901/2 cluster complex at redshift ~0.17 using restframe near-UV-optical SEDs, 24 micron IR data and HST morphologies from the STAGES dataset. The cluster sample is based on COMBO-17 redshifts with an rms precision of sigma_cz~2000 km/sec. We find that 'dusty red galaxies' and 'optically passive spirals' in A901/2 are largely the same phenomenon, and that they form stars at a substantial rate, which is only 4x lower than that in blue spirals at fixed mass. This star formation is more obscured than in blue galaxies and its optical signatures are weak. They appear predominantly in the stellar mass range of log M*/Msol=[10,11] where they constitute over half of the star-forming galaxies in the cluster; they are thus a vital ingredient for understanding the overall picture of star formation quenching in clusters. We find that the mean specific SFR of star-forming galaxies in the cluster is clearly lower than in the field, in contrast to the specific SFR properties of blue galaxies alone, which appear similar in cluster and field. Such a rich red spiral population is best explained if quenching is a slow process and morphological transformation is delayed even more. At log M*/Msol<10, such galaxies are rare, suggesting that their quenching is fast and accompanied by morphological change. We note, that edge-on spirals play a minor role; despite being dust-reddened they form only a small fraction of spirals independent of environment.

astro-ph↗