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We study the evolution of kinematically defined stellar discs in 10 Fornax-like clusters identified in the TNG50 run from the IllustrisTNG suite of cosmological simulations. We considered disc galaxies with present-day stellar mass M ⋆ ≥ 3 × 108 M⊙ and follow their evolution since first entering their host cluster. Very few stellar discs survive since falling in such dense environments, ranging from 40 per cent surviving to all being disrupted. Such survival rates are consistent with what reported earlier for the two more massive, Virgo-like clusters in TNG50. In absolute terms, however, the low number of present-day disc galaxies in Fornax-like clusters could be at odds with the presence of three edge-on disc galaxies in the central regions of the actual Fornax cluster, as delineated by the Fornax3D survey. When looking at the Fornax analogues from random directions and with the same selection function of Fornax3D, the probability of finding three edge-on disc galaxies in any one Fornax-like cluster in TNG50 is rather low, albeit not impossible. We also compared the stellar-population properties near the equatorial plane derived from integral-field spectroscopy for the three edge-ons in Fornax to similar line-of-sight integrated values for present-day disc galaxies in TNG50. For one of these, the very old and metal-rich stellar population of its disc cannot be matched by any the disc galaxies in TNG50, including objects in the field. We discuss possible interpretations of these findings, while pointing to future studies on passive cluster spirals as a way to further test state-of-the-art cosmological simulations. [ABSTRACT FROM AUTHOR]

We derived molecular gas fractions (fmol = Mmol/M*) and depletion times (τmol = Mmol/SFR) for 353 galaxies representative of the local star-forming population with 108.5 M⊙ < M* < 1010.5 M⊙ drawn from the ALLSMOG and xCOLDGASS surveys of CO(2−1) and CO(1−0) line emission. By adding constraints from low-mass galaxies and upper limits for CO non-detections, we find the median molecular gas fraction of the local star-forming population to be constant at log fmol = −0.99−0.19+0.22 log f mol = − 0. 99 − 0.19 + 0.22 $ \log f_{\mathrm{mol}}=-0.99^{+0.22}_{-0.19} $ , challenging previous reports of increased molecular gas fractions in low-mass galaxies. Above M* ∼ 1010.5 M⊙, we find the fmol versus M* relation to be sensitive to the selection criteria for star-forming galaxies. We tested the robustness of our results against different prescriptions for the CO-to-H2 conversion factor and different selection criteria for star-forming galaxies. The depletion timescale τmol weakly depends on M*, following a power law with a best-fit slope of 0.16 ± 0.03. This suggests that small variations in specific star formation rate (sSFR = SFR/M*) across the local main sequence of star-forming galaxies with M* < 1010.5 M⊙ are mainly driven by differences in the efficiency of converting the available molecular gas into stars. We tested these results against a possible dependence of fmol and τmol on the surrounding (group) environment of the targets by splitting them into centrals, satellites, and isolated galaxies, and find no significant variation between these populations. We conclude that the group environment is unlikely to have a large systematic effect on the molecular gas content of star-forming galaxies in the local Universe. [ABSTRACT FROM AUTHOR]

The 31 brightest galaxies (mB ≤ 15 mag) inside the virial radius of the Fornax cluster were observed from the centres to the outskirts with the Multi Unit Spectroscopic Explorer on the Very Large Telescope. These observations provide detailed high-resolution maps of the line-of-sight kinematics, line strengths of the stars, ionised gas reaching 2–3 Re for 21 early-type galaxies, and 1–2 Re for 10 late-type galaxies. The majority of the galaxies are regular rotators, with eight hosting a kinematically distinct core. Only two galaxies are slow rotators. The mean age, total metallicity, and [Mg/Fe] abundance ratio in the bright central region inside 0.5 Re and in the galaxy outskirts are presented. Extended emission-line gas is detected in 13 galaxies, most of them are late-type objects with wide-spread star formation. The measured structural properties are analysed in relation to the galaxies' position in the projected phase space of the cluster. This shows that the Fornax cluster appears to consist of three main groups of galaxies inside the virial radius: the old core; a clump of galaxies, which is aligned with the local large-scale structure and was accreted soon after the formation of the core; and a group of galaxies that fell in more recently. [ABSTRACT FROM AUTHOR]

Galaxies continuously reprocess their interstellar material. We can therefore expect changing dust grain properties in galaxies that have followed different evolutionary pathways. Determining the intrinsic dust grain mix of a galaxy helps in reconstructing its evolutionary history. Early-type galaxies occasionally display regular dust lanes in their central regions. Owing to the relatively simple geometry and composition of their stellar bodies, these galaxies are ideal to disentangle dust mix variations from geometric effects. We therefore modelled the various components of such a galaxy (FCC 167). We reconstructed its recent history and investigated the possible fate of the dust lane. Observations from MUSE and the Atacama Large Millimeter/submillimeter Array (ALMA) reveal a nested interstellar medium structure. An ionised-gas disc pervades the central regions of FCC 167, including those occupied by the main dust lane. Inward of the dust lane, we also find a disc/ring of cold molecular gas where stars are forming and HII regions contribute to the ionised-gas emission. Further in, the gas ionisation points towards an active galactic nucleus and the fuelling of a central supermassive black hole from its surrounding ionised and molecular reservoir. Observational constraints and radiative transfer models suggest the dust and gas are distributed in a ring-like geometry and the dust mix lacks small grains. The derived dust destruction timescales from sputtering in hot gas are short, and we conclude that the dust must be strongly self-shielding and clumpy or will quickly be eroded and disappear. Our findings show how detailed analyses of individual systems can complement statistical studies of dust-lane ETGs. [ABSTRACT FROM AUTHOR]

The newest generation of integral field unit spectrographs brings three-dimensional mapping of nearby galaxies one step closer. While the focus up to this point was mostly on stars and ionized gas, it is also possible to look at dust in a new, more complete way. Using MUSE science verification observations of NGC 5626, we map the interstellar matter in this dusty lenticular. We use the resolving power of MUSE to measure the optical attenuation with a spectral resolution of 6.25 Å, at physical scales of 0.1-1 kpc. The integrated attenuation curve of NGC 5626 shows a smooth, slightly steeper than Milky Way and SMC attenuation curves. Several sharp features are superimposed: we measure lower attenuation at spectral emission lines and higher attenuation for the sodium line doublet. No correlation was observed between sodium line strength and reddening by dust on spatially resolved scales. Additionally, the continuum attenuation was found to be independent from the Balmer decrement (tracing ionized gas attenuation). We model and interpret the variations in the attenuation curves of each spatial resolution element of NGC 5626.We find that the amount and distribution of dust along the line of sight is highly degenerate with any variation in the intrinsic extinction law. Our analysis shows that the interstellar matter in NGC 5626 resides in a regular and wellsettled disc. Our results preach caution in the application of simple recipes to de-redden global galaxy spectra and underlines the need for more realistic dust geometries when constructing such correction formulas. [ABSTRACT FROM AUTHOR]

Approximately 20 per cent of early-type galaxies host small nuclear stellar discs that are tens to a few hundred parsecs in size. Such discs are expected to be easily disrupted during major galactic encounters, hence their age serve to constrain their assembly history. We use VIsible MultiObject Spectrograph integral-field spectroscopic observations for the intermediate-mass E0 galaxy NGC 4458 and age-date its nuclear disc via high-resolution fitting of various model spectra. We find that the nuclear disc is at least 6 Gyr old. A clue to gain narrow limits to the stellar age is our knowledge of the nuclear disc contribution to the central surface brightness. The presence of an old nuclear disc, or the absence of disruptive encounters since z ∼ 0.6, for a small galaxy such as NGC 4458 which belongs to the Virgo cluster, may be consistent with a hierarchical picture for galaxy formation where the smallest galaxies assembles earlier and the crowded galactic environments reduce the incidence of galaxy mergers. On the other hand, NGC 4458 displays little or no bulk rotation except for a central kpc-scale kinematically decoupled core. Slow rotation and decoupled core are usually explained in terms of mergers. The presence and age of the nuclear disc constraint these mergers to have happened at high redshift. [ABSTRACT FROM AUTHOR]

Nuclear stellar discs (NSDs) can help to constrain the assembly history of their host galaxies, as long as we can assume them to be fragile structures that are disrupted during merger events. In this work we investigate the fragility of NSDs by means of N-body simulations reproducing the last phases of a galaxy encounter, when the nuclear regions of the two galaxies merge. For this, we exposed an NSD set in the gravitational potential of the bulge and supermassive black hole of a primary galaxy to the impact of the supermassive black hole from a secondary galaxy. We explored merger events of different mass ratios, from major mergers with a 1:1 mass ratio to intermediate and minor interactions with 1:5 and 1:10 ratios, while considering various impact geometries. We analyse the end results of such mergers from different viewing angles and look for possible photometric and kinematic signatures of the presence of a disc in the remnant surface density and velocity maps, while adopting detection limits from real observations. Our simulations show that indeed NSDs are fragile against major mergers, which leave little trace of NSDs both in images and velocity maps, while signatures of a disc can be found in the majority of the intermediate to minor-merger remnants and in particular when looking at their kinematics. These results show that NSDs could allow us to distinguish between these two modes of galaxy assembly, which may indeed pertain to different kinds of galaxies or galactic environments. [ABSTRACT FROM AUTHOR]

Nuclear stellar discs (NSDs) can help to constrain the assembly history of their host galaxies, as long as we can assume them to be fragile structures that are disrupted during merger events. In this work we investigate the fragility of NSDs by means of N-body simulations reproducing the last phases of a galaxy encounter, when the nuclear regions of the two galaxies merge. For this, we exposed an NSD set in the gravitational potential of the bulge and supermassive black hole of a primary galaxy to the impact of the supermassive black hole from a secondary galaxy. We explored merger events of different mass ratios, frommajor mergerswith a 1:1 mass ratio to intermediate and minor interactions with 1:5 and 1:10 ratios, while considering various impact geometries. We analyse the end results of such mergers from different viewing angles and look for possible photometric and kinematic signatures of the presence of a disc in the remnant surface density and velocity maps, while adopting detection limits from real observations. Our simulations show that indeed NSDs are fragile against major mergers, which leave little trace of NSDs both in images and velocity maps, while signatures of a disc can be found in the majority of the intermediate to minor-merger remnants and in particular when looking at their kinematics. These results show that NSDs could allow us to distinguish between these two modes of galaxy assembly, which may indeed pertain to different kinds of galaxies or galactic environments. [ABSTRACT FROM AUTHOR]

Nuclear stellar discs (NSDs), of a few tens to hundreds of parsec across, are a common and yet poorly studied feature of early-type galaxies. Still, such small discs represent a powerful tool to constrain the assembling history of galaxies, since they can be used to trace to the epoch when galaxies experienced their last major merger event. By studying the fraction and stellar age of NSDs, it is thus possible to test the predictions for the assembly history of early-type galaxies according to the current hierarchical paradigm for galaxy formation. In this paper we have produced the most comprehensive census of NSDs in nearby early-type galaxies by searching for such discs in objects within 100 Mpc and by using archival images from the Hubble Space Telescope. We found that NSDs are present in approximately 20 per cent of early-type galaxies, and that the fraction of galaxies with NSDs depends neither on their Hubble type nor on their galactic environment, whereas the incidence of NSDs appears to decline in the most massive systems. Furthermore, we have separated the light contribution of 12 such discs from that of their surrounding stellar bulge in order to extract their physical properties. This doubles the number of decomposed NSDs and although the derived values for their central surface brightness and scalelength are consistent with previous studies, they also give a hint of possible different characteristics due to different formation scenario between nuclear discs and other kinds of large galactic discs. [ABSTRACT FROM AUTHOR]

We present a study of the optical spectra of a sample of eight star-forming nuclear rings and the nuclei of their host galaxies. The spectra were obtained with the Intermediate dispersion Spectrograph and Imaging System spectrograph on the William Herschel Telescope and cover a wide range in wavelength, enabling the measurement of several stellar absorption features and gas emission lines. We compared the strength of the absorption lines to a variety of population synthesis models for the star formation history in the nuclear rings, including also the contribution of the older bulge and disc stellar components. In agreement with our previous investigation of the nuclear ring of NGC 4321, which was based on a more restricted number of line-strength indices, we find that the stars in our sample of nuclear rings have most likely formed over a prolonged period of time characterized by episodic bursts of star formation activity. Constant star formation is firmly ruled out by the present data, whereas a one-off formation event is an unlikely explanation for a common galactic component such as nuclear rings. The nuclear rings of NGC 4314 and NGC 7217 have distinct line-strength properties that set them apart from the rest of our sample, which are due to a larger contribution of bulge star in the observed spectra and, in the case of NGC 4314, to a younger stellar population in the ring. We have used emission-line measurements to constrain the physical conditions of the ionized gas within the rings, using the ratio of the [S ii]λλ6716, 6731 lines to estimate the density of the gas, and photoionization model grids within specific diagnostic diagrams to derive metallicity. We find that emission in all nuclear rings originates from H ii regions with electron densities typical for these kinds of objects, and that the rings are characterized by values for the gas metallicity ranging from slightly below to just above solar. We have also studied the spectra of the nuclei of our sample galaxies, all of which display emission lines. Consistent with previous studies for the nuclear activity and stellar populations, the majority of our nuclei appear to be dominated by old stellar populations and by Low-Ionization Nuclear Emission Region like emission. As 20 per cent of nearby spiral galaxies host nuclear rings that are presently forming massive stars, our finding of an episodic star formation history in nuclear rings implies that a significant population remains to be identified of young nuclear rings that are not presently in a massive star formation phase. Nuclear rings may thus be a much more common galactic component than presently known. [ABSTRACT FROM AUTHOR]

We present the ionized gas kinematics of the SB0 galaxy NGC 4435 from spectra obtained with the Space Telescope Imaging Spectrograph. This galaxy has been selected on the basis of its ground-based spectroscopy, for displaying a position–velocity diagram consistent with the presence of a circumnuclear Keplerian disc rotating around a supermassive black hole (SMBH). We obtained the Hα and [N ii] λ6583 kinematics in the galaxy nucleus along the major axis and two parallel offset positions. We built a dynamical model of the gaseous disc taking into account the whole bi-dimensional velocity field and the instrumental setup. For the mass of the central SMBH, we found an upper limit of at the 3σ level. This indicates that the mass of the SMBH of NGC 4435 is lower than the one expected from the and near-infrared relationships. [ABSTRACT FROM AUTHOR]

We combine data from ALMA and MUSE to study the resolved (∼300 pc scale) star formation relation (star formation rate, SFR, versus molecular gas surface density) in cluster galaxies. Our sample consists of nine Fornax cluster galaxies, including spirals, ellipticals, and dwarfs, covering a stellar mass range of ∼108.8–1011 M⊙. CO(1-0) and extinction corrected Hα were used as tracers for the molecular gas mass and SFR, respectively. We compare our results with Kennicutt and Bigiel et al. Furthermore, we create depletion time maps to reveal small-scale variations in individual galaxies. We explore these further in FCC290, using the 'uncertainty principle for star formation' (Kruijssen & Longmore) to estimate molecular cloud lifetimes, which we find to be short (<10 Myr) in this galaxy. Galaxy-averaged depletion times are compared with other parameters such as stellar mass and cluster-centric distance. We find that the star formation relation in the Fornax cluster is close to those from Kennicutt and Bigiel et al. but overlaps mostly with the shortest depletion times predicted by Bigiel et al. This slight decrease in depletion time is mostly driven by dwarf galaxies with disturbed molecular gas reservoirs close to the virial radius. In FCC90, a dwarf galaxy with a molecular gas tail, we find that depletion times are a factor ≳10 higher in its tail than in its stellar body. [ABSTRACT FROM AUTHOR]

We apply a population-orbit superposition metho1d to 16 galaxies in the Fornax cluster observed with MUSE/VLT in the context of the Fornax3D project. By fitting the luminosity distribution, stellar kinematics, and age and metallicity maps simultaneously, we obtained the internal stellar orbit distribution, as well as the age and metallicity distribution of stars on different orbits for each galaxy. Based on the model, we decompose each galaxy into a dynamically cold disk (orbital circularity -z - 0:8) and a dynamically hot nondisk component (orbital circularity -z < 0:8), and obtain the surface-brightness, age, and metallicity radial profiles of each component. The galaxy infall time into the cluster is strongly correlated with galaxy cold-disk age with older cold disks in ancient infallers. We quantify the infall time tinfall of each galaxy with its cold-disk age using a correlation calibrated with TNG50 cosmological simulations. For galaxies in the Fornax cluster, we found that the luminosity fraction of cold disk in galaxies with tinfall > 8 Gyr are a factor of ~4 lower than in more recent infallers while controlling for total stellar mass. Nine of the 16 galaxies have spatially extended cold disks, and most of them show positive or zero age gradients; stars in the inner disk are ~2-5 Gyr younger than that in the outer disk, in contrast to the expectation of inside-out growth. Our results indicate that the assembly of cold disks in galaxies is strongly affected by their infall into clusters, by either removal of gas in outer regions or even tidally stripping or heating part of the pre-existing disks. Star formation in outer disks can stop quickly after the galaxy falls into the cluster, while star formation in the inner disks can last for a few Gyrs more, building the positive age gradient measured in cold disks. [ABSTRACT FROM AUTHOR]

Variations of the stellar initial mass function (IMF) in external galaxies have been inferred from a variety of independent probes. Yet the physical conditions causing these variations remain largely unknown. In this work, we explore new spatially resolved measurements of the IMF for three edge-on lenticular galaxies in the Fornax cluster. We utilize existing orbit-based dynamical models in order to fit the new IMF maps within an orbital framework. We find that, within each galaxy, the high-angular momentum disc-like stars exhibit an IMF which is rich in dwarf stars. The centrally concentrated pressure-supported orbits exhibit similarly dwarf-rich IMF. Conversely, orbits at large radius which have intermediate angular momentum exhibit IMF which are markedly less dwarf-rich relative to the other regions of the same galaxy. Assuming that the stars which reside, in the present-day, on dynamically hot orbits at large radii are dominated by accreted populations, we interpret these findings as a correlation between the dwarf-richness of a population of stars, and the mass of the host in which it formed. Specifically, deeper gravitational potentials would produce more dwarf-rich populations, resulting in the relative deficiency of dwarf stars which originated in the lower mass accreted satellites. The central and high-angular momentum populations are likely dominated by in situ stars, which were formed in the more massive host itself. There are also global differences between the three galaxies studied here, of up to ∼0.3 dex in the IMF parameter ξ. We find no local dynamical or chemical property which alone can fully account for the IMF variations. [ABSTRACT FROM AUTHOR]

Hot atmospheres pervading galaxy clusters, groups, and early-type galaxies are rich in metals, produced during epochs and diffused via processes that are still to be determined. While this enrichment has been routinely investigated in clusters, metals in lower mass systems are more challenging to probe with standard X-ray exposures and spectroscopy. In this paper, we focus on very deep XMM–Newton (∼350 ks) observations of NGC 1404, a massive elliptical galaxy experiencing ram-pressure stripping of its hot atmosphere while infalling towards the centre of the Fornax cluster, with the aim to derive abundances through its hot gas extent. Importantly, we report the existence of a new fitting bias – the 'double Fe bias' – leading to an underestimate of the Fe abundance when two thermal components cannot realistically model the complex temperature structure present in the outer atmosphere of the galaxy. Contrasting with the 'metal conundrum' seen in clusters, the Fe and Mg masses of NGC 1404 are measured 1–2 orders of magnitude below what stars and supernovae could have reasonably produced and released. In addition, we note the remarkable Solar abundance ratios of the galaxy's halo, different from its stellar counterpart but similar to the chemical composition of the ICM of rich clusters. Completing the clusters regime, all these findings provide additional support towards a scenario of early enrichment, at play over two orders of magnitude in mass. A few peculiar and intriguing features, such as a possible double metal peak as well as an apparent ring of enhanced Si near the galaxy core, are also discussed. [ABSTRACT FROM AUTHOR]

Photometry and long-slit spectroscopy are presented for a sample of six galaxies with a low surface-brightness stellar disc and a bulge. The characterizing parameters of the bulge and disc components were derived by means of a two-dimensional photometric decomposition of the images of the sample galaxies. Their surface-brightness distribution was assumed to be the sum of the contribution of a Sérsic bulge and an exponential disc, with each component being described by elliptical and concentric isophotes of constant ellipticity and position angle. The stellar and ionized-gas kinematics were measured along the major and minor axes in half of the sample galaxies, whereas the other half was observed only along two diagonal axes. Spectra along two diagonal axes were obtained also for one of the objects with major and minor axis spectra. The kinematic measurements extend in the disc region out to a surface-brightness level mag arcsec−2, reaching in all cases the flat part of the rotation curve. The stellar kinematics turns out to be more regular and symmetric than the ionized-gas kinematics, which often shows the presence of non-circular, off-plane and non-ordered motions. This raises the question about the reliability of the use of the ionized gas as the tracer of the circular velocity in the modelling of the mass distribution, in particular in the central regions of low surface-brightness galaxies. [ABSTRACT FROM AUTHOR]

We present near-infrared (NIR) adaptive optics-assisted spectroscopic observations of the absorption bands towards the centre of the giant elliptical galaxy NGC 1399. The observations were made with NAOS-CONICA (on the European Southern Observatory's Very Large Telescope) and have a full width at half-maximum resolution of 0.15 arcsec (14 pc). Kinematic analysis of the observations reveals a decoupled core and strongly non-Gaussian line-of-sight velocity profiles in the central 0.2 arcsec (19 pc). NIR imaging also indicates an asymmetric elongation of the central isophotes in the same region. We use spherical orbit-superposition models to interpret the kinematics, using a set of orthogonal ‘eigen-velocity profiles’ that allow us to fit models directly to spectra. The models require a central black hole of mass , with a strongly tangentially biased orbit distribution in the inner 40 pc. [ABSTRACT FROM AUTHOR]

We present the kinematics and photometry of the stars and of the ionized gas near the centre of the S0 galaxy NGC 4036. Dynamical models based on the Jeans equation have been constructed from the stellar data to determine the gravitational potential in which the ionized gas is expected to orbit. Inside 10 arcsec, the observed gas rotation curve falls well short of the predicted circular velocity. Over a comparable radial region the observed gas velocity dispersion is far higher than that expected from thermal motions or small-scale turbulence, corroborating that the gas cannot be following the streamlines of nearly closed orbits. We explore several avenues to understand the dynamical state of the gas. (1) We treat the gas as a collisionless ensemble of cloudlets and apply the Jeans equation to it; this modelling shows that inside 4 arcsec the gas velocity dispersion is just high enough to explain quantitatively the absence of rotation. (2) Alternatively, we explore whether the gas may arise from the ‘just shed’ mass-loss envelopes of the bulge stars, in which case their kinematics should simply mimic that of the stars; the latter approach matches the data better than (1), but still fails to explain the low velocity dispersion and slow rotation velocity of the gas for 5

The stellar initial mass function (IMF) regulates the baryonic cycle within galaxies, and is a key ingredient for translating observations into physical quantities. Although it was assumed to be universal for decades, there is now growing observational evidence showing that the center of massive early-type galaxies hosts a larger population of low-mass stars than is expected based on observations from the Milky Way. Moreover, these variations in the IMF have been found to be related to radial metallicity variations in massive galaxies. We present here a two-dimensional stellar population analysis of the massive lenticular galaxy FCC 167 (NGC 1380) as part of the Fornax3D project. Using a newly developed stellar population fitting scheme, we derive a full two-dimensional IMF map of an early-type galaxy. This two-dimensional analysis allows us go further than a radial analysis, showing how the metallicity changes along a disk-like structure while the IMF follows a distinct, less disky distribution. Thus, our findings indicate that metallicity cannot be the sole driver of the observed radial IMF variations. In addition, a comparison with the orbital decomposition shows suggestive evidence of a coupling between stellar population properties and the internal dynamical structure of FCC 167, where metallicity and IMF maps seem to track the distribution of cold and warm orbits, respectively. [ABSTRACT FROM AUTHOR]

We have used deep MUSE observations to perform a stellar-kinematic and population analysis of FCC 153 and FCC 177, two edge-on S0 galaxies in the Fornax cluster. The geometrical definition of the different structural components of these two galaxies allows us to describe the nature of their thick disks. These are both old, relatively metal poor and [Mg/Fe]-enhanced, and their star formation history (SFH) reveals a minor younger component whose chemical properties suggest its later accretion. Moreover, the outer regions of these geometrically defined thick disks show higher values of metallicity and lower values of [Mg/Fe]. These stars probably formed in the thin-disk region and they were dynamically heated to form the flares present in these two galaxies. We propose different formation scenarios for the three populations of these thick disks: in-situ formation, accretion and disk heating. A clear distinction in age is found between the metal poor and [Mg/Fe]-enhanced thick disks (old, ∼12 − 13 Gyr), and the metal rich and less [Mg/Fe]-enhanced thin disks (young, ∼4 − 5 Gyr). These two galaxies show signs of relatively recent star formation in their thin disks and nuclear regions. While the thin disks show more continuous SFHs, the nuclei display a rather bursty SFH. These two galaxies are located outside of the densest region of the Fornax cluster where FCC 170 resides. This other edge-on S0 galaxy has recently been studied, and we have compared and discussed our results with this previous study. The differences between these three galaxies, at different distances from the cluster center, suggest that the environment can have a strong effect on the galaxy evolutionary path. [ABSTRACT FROM AUTHOR]

We present and discuss the stellar kinematics and populations of the S0 galaxy FCC 170 (NGC 1381) in the Fornax cluster, using deep MUSE data from the Fornax 3D survey. We show the maps of the first four moments of the stellar line-of-sight velocity distribution and of the mass-weighted mean stellar age, metallicity, and [Mg/Fe] abundance ratio. The high-quality MUSE stellar kinematic measurements unveil the structure of this massive galaxy: a nuclear disk, a bar seen as a boxy bulge with a clear higher-velocity-dispersion X shape, a fast-rotating and flaring thin disk and a slower rotating thick disk. Whereas their overall old age makes it difficult to discuss differences in the formation epoch between these components, we find a clear-cut distinction between metal-rich and less [Mg/Fe]-enhanced populations in the thin-disk, boxy-bulge and nuclear disk, and more metal-poor and [Mg/Fe]-enhanced stars in the thick disk. Located in the densest region of the Fornax cluster, where signs of tidal stripping have been recently found, the evolution of FCC 170 might have been seriously affected by its environment. We discuss the possibility of its "preprocessing" in a subgroup before falling into the present-day cluster, which would have shaped this galaxy a long time ago. The thick disk displays a composite star formation history, as a significant fraction of younger stars co-exist with the main older thick-disk population. The former subpopulation is characterized by even lower-metallicity and higher-[Mg/Fe] values, suggesting that these stars formed later and faster in a less chemically evolved satellite, which was subsequently accreted. Finally, we discuss evidence that metal-rich and less [Mg/Fe]-enhanced stars were brought in the outer parts of the thick disk by the flaring of the thin disk. [ABSTRACT FROM AUTHOR]

We present new stringent limits on the mass M• of the central supermassive black hole for a sample of seven nearby galaxies. Our M• estimates are based on the dynamic modeling of the central width of the nebular emission lines measured over sub-arcsecond apertures with the Hubble Space Telescope. The central stellar velocity dispersion, σc, of the sample galaxies is derived from new long-slit spectra from ground-based observations and the bulge effective radius is obtained from a two-dimensional photometric decomposition of the i-band images from the Sloan Digital Sky Survey. The derived stringent M• limits run parallel and above the M•− σc relation, with no systematic trend depending on the galaxy distance or morphology. This gives further support to previous findings suggesting that the nuclear gravitational potential is remarkably well traced by the width of the nebular lines when the gas is centrally peaked. With our investigation, the number of galaxies with stringent M• limits obtained from the nebular line width increases to 114 and can be used for studying the scaling relations between M• and properties of their host galaxies. [ABSTRACT FROM AUTHOR]

We present our mass estimate of the central black hole in the isolated spiral galaxy NGC 4414. Using natural guide star adaptive optics assisted observations with the Gemini Near-Infrared Integral Field Spectrometer (NIFS) and the natural seeing Gemini Multi-Object Spectrographs-North (GMOS), we derived two-dimensional stellar kinematic maps of NGC 4414 covering the central 1:5 arcsec and 10 arcsec, respectively, at a NIFS spatial resolution of 0.13 arcsec. The kinematic maps reveal a regular rotation pattern and a central velocity dispersion dip down to around 105 km s-1. We constructed dynamical models using two different methods: Jeans anisotropic dynamical modeling and axisymmetric Schwarzschild modeling. Both modeling methods give consistent results, but we cannot constrain the lower mass limit and only measure an upper limit for the black hole mass of M⊙ BH = 1:56 - 106 M (at 3σ level) which is at least 1σ below the recent MBH - σe relations. Further tests with dark matter, mass-to-light ratio variation and different light models confirm that our results are not dominated by uncertainties. The derived upper limit mass is not only below the MBH -σe relation, but is also five times lower than the lower limit black hole mass anticipated from the resolution limit of the sphere of influence. This proves that via high quality integral field data we are now able to push black hole measurements down to at least five times less than the resolution limit. [ABSTRACT FROM AUTHOR]

ABSTRACT We present ground-based MDM Observatory V-band and Spitzer/InfraRed Array Camera 3.6-m-band photometric observations of the 72 representative galaxies of the SAURON survey. Galaxies in our sample probe the elliptical E, lenticular S0 and spiral Sa populations in the nearby Universe, both in field and cluster environments. We perform aperture photometry to derive homogeneous structural quantities. In combination with the SAURON stellar velocity dispersion measured within an effective radius (σe), this allows us to explore the location of our galaxies in the colour-magnitude, colour-σe, Kormendy, Faber-Jackson and Fundamental Plane scaling relations. We investigate the dependence of these relations on our recent kinematical classification of early-type galaxies (i.e. slow/fast rotators) and the stellar populations. Slow rotator and fast rotator E/S0 galaxies do not populate distinct locations in the scaling relations, although slow rotators display a smaller intrinsic scatter. We find that Sa galaxies deviate from the colour-magnitude and colour-σe relations due to the presence of dust, while the E/S0 galaxies define tight relations. Surprisingly, extremely young objects do not display the bluest ( V−[3.6]) colours in our sample, as is usually the case in optical colours. This can be understood in the context of the large contribution of thermally pulsing asymptotic giant branch stars to the infrared, even for young populations, resulting in a very tight ( V−[3.6])-σe relation that in turn allows us to define a strong correlation between metallicity and σe. Many Sa galaxies appear to follow the Fundamental Plane defined by E/S0 galaxies. Galaxies that appear offset from the relations correspond mostly to objects with extremely young populations, with signs of ongoing, extended star formation. We correct for this effect in the Fundamental Plane, by replacing luminosity with stellar mass using an estimate of the stellar mass-to-light ratio, so that all galaxies are part of a tight, single relation. The new estimated coefficients are consistent in both photometric bands and suggest that differences in stellar populations account for about half of the observed tilt with respect to the virial prediction. After these corrections, the slow rotator family shows almost no intrinsic scatter around the best-fitting Fundamental Plane. The use of a velocity dispersion within a small aperture (e.g. Re/8) in the Fundamental Plane results in an increase of around 15 per cent in the intrinsic scatter and an average 10 per cent decrease in the tilt away from the virial relation. [ABSTRACT FROM AUTHOR]

We study resolution effects in numerical simulations of gas-rich and gas-poor major mergers, and show that the formation of slowly rotating elliptical galaxies often requires a resolution that is beyond the present-day standards to be properly modelled. Our sample of equal-mass merger models encompasses various masses and spatial resolutions, ranging from about 200 pc and 105 particles per component (stars, gas and dark matter), i.e. a gas mass resolution of , typical of some recently published major merger simulations, to up to 32 pc and in simulations using collisionless particles and gas particles, among the highest resolutions reached so far for gas-rich major merger of massive disc galaxies. We find that the formation of fast-rotating early-type galaxies, that are flattened by a significant residual rotation, is overall correctly reproduced at all such resolutions. However, the formation of slow-rotating early-type galaxies, which have a low-residual angular momentum and are supported mostly by anisotropic velocity dispersions, is strongly resolution-dependent. The evacuation of angular momentum from the main stellar body is largely missed at standard resolution, and systems that should be slow rotators are then found to be fast rotators. The effect is most important for gas-rich mergers, but is also witnessed in mergers with an absent or modest gas component (0–10 per cent in mass). The effect is robust with respect to our initial conditions and interaction orbits, and originates in the physical treatment of the relaxation process during the coalescence of the galaxies. Our findings show that a high-enough resolution is required to accurately model the global properties of merger remnants and the evolution of their angular momentum. The role of gas-rich mergers of spiral galaxies in the formation of slow-rotating ellipticals may therefore have been underestimated. Moreover, the effect of gas in a galaxy merger is not limited to helping the survival/rebuilding of rotating disc components: at high resolution, gas actively participates in the relaxation process and the formation of slowly rotating stellar systems. [ABSTRACT FROM AUTHOR]

Following the study of Darg et al., we explore the environments, optical colours, stellar masses, star formation and active galactic nucleus activity in a sample of 3003 pairs of merging galaxies drawn from the Sloan Digital Sky Survey using visual classifications from the Galaxy Zoo project. While Darg et al. found that the spiral-to-elliptical ratio in (major) mergers appeared higher than that of the global galaxy population, no significant differences are found between the environmental distributions of mergers and a randomly selected control sample. This makes the high occurrence of spirals in mergers unlikely to be an environmental effect and must therefore arise from differing time-scales of detectability for spirals and ellipticals. We find that merging galaxies have a wider spread in colour than the global galaxy population, with a significant blue tail resulting from intense star formation in spiral mergers. Galaxies classed as star-forming using their emission-line properties have average star formation rates approximately doubled by the merger process though star formation is negligibly enhanced in merging elliptical galaxies. We conclude that the internal properties of galaxies significantly affect the time-scales over which merging systems can be detected (as suggested by recent theoretical studies) which leads to spirals being ‘over-observed’ in mergers. We also suggest that the transition mass , noted by Kauffmann et al., below which ellipticals are rare could be linked to disc survival/destruction in mergers. [ABSTRACT FROM AUTHOR]

We present the largest, most homogeneous catalogue of merging galaxies in the nearby Universe obtained through the Galaxy Zoo project – an interface on the World Wide Web enabling large-scale morphological classification of galaxies through visual inspection of images from the Sloan Digital Sky Survey (SDSS). The method converts a set of visually inspected classifications for each galaxy into a single parameter (the ‘weighted-merger-vote fraction,’ fm) which describes our confidence that the system is part of an ongoing merger. We describe how fm is used to create a catalogue of 3003 visually selected pairs of merging galaxies from the SDSS in the redshift range . We use our merger sample and values of fm applied to the SDSS Main Galaxy Spectral sample to estimate that the fraction of volume-limited major mergers in the nearby Universe is where is a correction factor for spectroscopic incompleteness. Having visually classified the morphologies of the constituent galaxies in our mergers, we find that the spiral-to-elliptical ratio of galaxies in mergers is higher by a factor of ∼2 relative to the global population. In a companion paper, we examine the internal properties of these merging galaxies and conclude that this high spiral-to-elliptical ratio in mergers is due to a longer time-scale over which mergers with spirals are detectable compared to mergers with ellipticals. [ABSTRACT FROM AUTHOR]

Photometry and long-slit spectroscopy are presented for 14 S0 and spiral galaxies of the Fornax, Eridanus and Pegasus cluster, and NGC 7582 group. The structural parameters of the galaxies are derived from the R-band images by performing a two-dimensional photometric decomposition of the surface brightness distribution. This is assumed to be the sum of the contribution of a bulge and disc component characterized by elliptical and concentric isophotes with constant (but possibly different) ellipticity and position angles. The rotation curves and velocity dispersion profiles are measured from the spectra obtained along the major axis of galaxies. The radial profiles of the Hβ, Mg and Fe line-strength indices are presented too. Correlations between the central values of and σ are found. The age, metallicity and α/Fe enhancement of the stellar population in the centre and at the radius where bulge and disc give the same contribution to the total surface brightness are obtained using stellar population models with variable element abundance ratios. Three classes of bulges are identified. The youngest bulges (∼2 Gyr) with ongoing star formation, intermediate-age bulges (4–8 Gyr) have solar metallicity, and old bulges (∼10 Gyr) have high metallicity. Most of the sample bulges display solar α/Fe enhancement, no gradient in age and a negative gradient of metallicity. The presence of negative gradient in the metallicity radial profile favours a scenario with bulge formation via dissipative collapse. This implies strong inside-out formation that should give rise to a negative gradient in the α/Fe enhancement too. But, no gradient is measured in the [α/Fe] radial profiles for all the galaxies, except for NGC 1366. In this galaxy there is a kinematically decoupled component, which is younger than the rest of host bulge. It possibly formed by enriched material probably acquired via interaction or minor merging. The bulge of NGC 1292 is the most reliable pseudo-bulge of our sample. The properties of its stellar population are consistent with a slow build-up within a scenario of secular evolution. [ABSTRACT FROM AUTHOR]

We present the first large-scale study of E+A galaxies that incorporates photometry in the ultraviolet (UV) wavelengths. E+A galaxies are ‘post-starburst’ systems, with strong Balmer absorption lines indicating significant recent star formation, but without [O ii] and Hα emission lines which are characteristic of ongoing star formation. The starburst that creates the E+A galaxy typically takes place within the last Gyr and creates a high fraction (20–60 per cent) of the stellar mass in the remnant over a short time-scale (<0.1 Gyr). We find a tight correlation between the luminosity of our E+A galaxies and the implied star formation rate (SFR) during the starburst. While low-luminosity E+As [ ] exhibit implied SFRs of less than , their luminous counterparts [ ] show SFRs greater than 300 and as high as , suggesting that luminous and ultra-luminous infrared galaxies in the low-redshift Universe could be the progenitors of massive nearby E+A galaxies. We perform a comprehensive study of the characteristics of the quenching that truncates the starburst in E+A systems. We find that, for galaxies less massive than , the quenching efficiency decreases as the galaxy mass increases. However, for galaxies more massive than , this trend is reversed and the quenching efficiency increases with galaxy mass. Noting that the mass threshold at which this reversal occurs is in excellent agreement with the mass above which active galactic nuclei (AGN) become significantly more abundant in nearby galaxies, we use simple energetic arguments to show that the bimodal behaviour of the quenching efficiency is consistent with AGN and supernovae (SN) being the principal sources of negative feedback above and below , respectively. The arguments assume that quenching occurs through the mechanical ejection or dispersal of the gas reservoir and that, in the high-mass regime , the Eddington ratios in this sample of galaxies scale as , where . Finally, we use our E+A sample to estimate the time it takes for galaxies to migrate from the blue cloud to the red sequence. We find migration times between 1 and 5 Gyr, with a median value of 1.5 Gyr. [ABSTRACT FROM AUTHOR]

Abstract: We give two examples of spiral galaxies that show non-circular gas motions in the inner kiloparsecs, from SAURON integral field spectroscopy. We use harmonic decomposition of the velocity field of the ionized gas to study the underlying mass distribution, employing linear theory. The higher order harmonic terms and the main kinematic features of the observed data are consistent with an analytically constructed simple bar model. We also present maps of a number of strong absorption lines in M 100, derive simple stellar populations and correlate them with features in the gas kinematics. [Copyright &y& Elsevier]

Abstract: We present the results of deep Westerbork Synthesis Radio Telescope observations of the neutral hydrogen in 12 nearby elliptical and lenticular galaxies selected from a representative sample of nearby galaxies that were studied earlier at optical wavelengths with the integral-field spectrograph sauron. The observed objects are field galaxies, or (in two cases) are located in poor-group environments. We detect Hi in 70% of the galaxies. This detection rate is much higher than in previous, shallower single-dish surveys, and is similar to that for the ionised gas. The results suggest that at faint detection levels the presence of Hi is a relatively common characteristic of field early-type galaxies. The presence of regular disc-like structures is as common as Hi in offset clouds and tails. All galaxies where Hi is detected also contain ionised gas, whereas no Hi is found around galaxies without ionised gas. Galaxies with regular Hi discs tend to have strong emission from ionised gas. In these cases, the similar kinematics of the neutral hydrogen and ionised gas suggest that they form one structure. We do not find a trend between the presence of Hi and the global age of the stellar population or with the global dynamical characteristics of the galaxies. If fast and slow rotators represent the relics of different formation paths, this does not appear in the presence and characteristics of the Hi. The links observed between the large-scale gas and the characteristics on the nuclear scale (e.g. the presence of kinematically decoupled cores and radio continuum emission), suggest that for the majority of the cases the gas is acquired through merging, but the lack of correlation with the stellar-population age suggests that smooth, cold accretion could be an alternative scenario, at least in some galaxies. In either case, the data suggest that early-type galaxies continue to build-up their mass to the present. [Copyright &y& Elsevier]

We introduce the Galaxy IFU Spectroscopy Tool (GIST), a convenient, all-in-one and multi-purpose tool for the analysis and visualisation of already reduced (integral-field) spectroscopic data. In particular, the pipeline performs all steps from read-in and preparation of data to its scientific analysis and visualisation in publication-quality plots. The code measures stellar kinematics and non-parametric star formation histories using the pPXF routine (Cappellari & Emsellem 2004; Cappellari 2017), performs an emission-line analysis with the GandALF procedure (Sarzi et al. 2006; Falcón-Barroso et al. 2006), and determines absorption line-strength indices and their corresponding single stellar population equivalent population properties (Kuntschner et al.2006; Martín-Navarro et al. 2018). The dedicated visualisation routine Mapviewer facilitates the access of all data products in a sophisticated graphical user interface with fully interactive plots. [ABSTRACT FROM AUTHOR]

Context. Star-forming nuclear rings in barred galaxies are common in nearby spirals, and their detailed study can lead to important insights into the evolution of galaxies, their bars and their central regions. We present integral field spectroscopic observations obtained with SAURON of the bar and circumnuclear region of the barred spiral galaxy M100, complemented by new Spitzer Space Telescope imaging of the region. Aims. We use these data to enhance our understanding of the formation, evolution and current properties of the bar and ring. Methods. We derive the kinematics of the gas and the stars and quantify circular and non-circular motions using kinemetry. We analyse this in conjunction with the optical and infrared morphology, and our previously published dynamical modelling. By comparing line indices to simple stellar population models we estimate the ages and metallicities of the stellar populations present within the region, especially in and around the ring. Results. The stellar and gaseous velocity fields are remarkably similar, and we confirm that the velocity fields show strong evidence for non-circular motions due to the bar and the associated density wave. These are strongest just outside the nuclear ring, where our kinemetric analysis indicates inflow across the spiral armlets and into the ring region. The line strength maps all indicate the presence of a younger population within this ring, but detailed modelling of the line strengths shows that in addition to this young population, old stars are present. These old stars must have been formed in an event of massive star formation which produced the bulk of the mass, and which ended some 3 Gyr ago, a constraint set by the age of the stars in the bar and the nucleus. Our best-fitting model is one in which the current star formation is but the latest of a series of relatively short bursts of star formation which have occurred for the last 500 Myr or so. A clear bipolar azimuthal age gradient is seen within the ring, with the youngest stars occurring near where the bar dust lanes connect with the ring. Conclusions. Our kinematic and morphological results all confirm the picture in which the nuclear ring in M100, considered typical, is fed by gas flowing in from the disc under the action of the bar, is slowed down near a pair of resonances, and forms significant amounts of massive stars. Detailed stellar population modelling shows how the underlying bulge and disc were put in place a number of Gyr ago, and that the nuclear ring has been forming stars since about 500 Myr ago in a stable succession of bursts. This confirms that nuclear rings of this kind can form under the influence of a resonant structure set up by a bar, and proves that they are stable features of a galaxy rather than one-off starburst events. [ABSTRACT FROM AUTHOR]

We present the results of deep Westerbork Synthesis Radio Telescope observations of neutral hydrogen in 12 nearby elliptical and lenticular galaxies. The selected objects come from a representative sample of nearby galaxies earlier studied at optical wavelengths with the integral-field spectrograph SAURON (Spectrographic Areal Unit for Research on Optical Nebulae). They are field galaxies, or (in two cases) located in poor group environments. We detect H i– both in regular discs as well as in clouds and tails offset from the host galaxy – in 70 per cent of the galaxies. This detection rate is much higher than in previous, shallower single-dish surveys, and is similar to that for the ionized gas. The results suggest that at faint detection levels the presence of H i is a relatively common characteristic of field early-type galaxies, confirming what was suggested twenty years ago by Jura based on IRAS observations. The observed total H i masses range between a few times 106 to just over . The presence of regular disc-like structures is a situation as common as H i in offset clouds and tails around early-type galaxies. All galaxies where H i is detected also contain ionized gas, whereas no H i is found around galaxies without ionized gas. Galaxies with regular H i discs tend to have strong emission from ionized gas. In these cases, the similar kinematics of the neutral hydrogen and ionized gas suggest that they form one structure. The kinematical axis of the stellar component is nearly always misaligned with respect to that of the gas. We do not find a clear trend between the presence of H i and the global age of the stellar population or the global dynamical characteristics of the galaxies. More specifically, H i detections are uniformly spread through the diagram. If fast and slow rotators – galaxies with high and low specific angular momentum – represent the relics of different formation paths, this does not appear in the presence and characteristics of the H i. Our observations support the idea that gas accretion is common and does not happen exclusively in peculiar early-type galaxies. The links observed between the large-scale gas and the characteristics on the nuclear scale (e.g. the presence of kinematically decoupled cores, radio continuum emission etc.) suggest that for the majority of the cases the gas is acquired through merging, but the lack of correlation with the stellar population age suggests that smooth, cold accretion could be an alternative scenario, at least in some galaxies. In either case, the data suggest that early-type galaxies continue to build their mass up to the present. [ABSTRACT FROM AUTHOR]

We report recent results from the photometric follow-up study we are conducting in the context of the SAURON project. We use ground-based MDM V-band and Spitzer/IRAC 3.6 µm imaging to characterise our sample of E, S0 and Sa galaxies photometrically. Combined with SAURON integral-field spectroscopic observations, this information allows us to explore and understand the location of these galaxies on the Fundamental Plane relation, providing an important diagnostic tool to study their formation and evolution. [ABSTRACT FROM AUTHOR]