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Schwarzschild dynamical models are now regularly employed in large surveys of galaxies in the local and distant Universe to derive information on galaxies' intrinsic properties such as their orbital structure and their (dark matter and stellar) mass distribution. Comparing the internal orbital structures and mass distributions of galaxies in the distant Universe with simulations is key to understanding what physical processes are responsible for shaping galaxy properties. However, it is first crucial to understand whether observationally derived properties are directly comparable with intrinsic ones in simulations. To assess this, we build Schwarzschild dynamical models for MUSE-like IFS (integral field spectroscopy) cubes (constructed to be like those obtained by the Middle Ages Galaxy Properties with Integral Field Spectroscopy, MAGPI survey) of 75 galaxies at |$z \sim$| 0.3 from the eagle simulations. We compare the true particle-derived properties with the galaxies' model-derived properties. In general, we find that the models can recover the true galaxy properties qualitatively well, with the exception of the enclosed dark matter, where we find a median offset of 48 per cent, which is due to the assumed Navarro–Frenk–White profile not being able to reproduce the dark matter distribution in the inner region of the galaxies. We then compare our model-derived properties with Schwarzschild models-derived properties of observed MAGPI galaxies and find good agreement between MAGPI and eagle : the majority of our galaxies (57 per cent) have non-oblate shapes within 1 effective radius. More triaxial galaxies show higher fractions of hot orbits in their inner regions and tend to be more radially anisotropic. [ABSTRACT FROM AUTHOR]

We use the 'Middle Ages Galaxy Properties with Integral field spectroscopy' (MAGPI) survey to investigate whether galaxies have evolved in the distribution of their stellar angular momentum in the past 3–4 Gyr, as probed by the observational proxy for spin, λR. We use 2D stellar kinematics to measure λR along with detailed photometric models to estimate galaxy ellipticity. The combination of these measurements quantifies the kinematic classes of 'fast rotators' and the rarer 'slow rotators', which show no regular rotation in their line-of-sight velocity fields. We compare 51 MAGPI galaxies with log10 (M ⋆/M⊙) > 10 to carefully drawn samples of MaNGA galaxies in the local Universe, selected to represent possible descendants of the MAGPI progenitors. The EAGLE simulations are used to identify possible evolutionary pathways between the two samples, explicitly accounting for progenitor bias in our results and the varied evolutionary pathways a galaxy might take between the two epochs. We find that the occurrence of slow rotating galaxies is unchanged between the MAGPI (z ∼ 0.3) and MaNGA (z ∼ 0) samples, suggesting the massive slow rotator population was already in place ∼4 Gyr ago and has not accumulated since. There is a hint of the MAGPI sample having an excess of high λR galaxies compared to the MaNGA sample, corresponding to more ordered rotation, but statistically the samples are not significantly different. The large-scale stellar kinematics, as quantified through the λR parameter, of galaxies at z ∼ 0.3 have already evolved into the diversity of structures seen today in the local Universe. [ABSTRACT FROM AUTHOR]

FRB 20210912A is a fast radio burst (FRB), detected and localized to subarcsecond precision by the Australian Square Kilometre Array Pathfinder. No host galaxy has been identified for this burst despite the high precision of its localization and deep optical and infrared follow-up, to 5σ limits of R  = 26.7 mag and K s = 24.9 mag with the Very Large Telescope. The combination of precise radio localization and deep optical imaging has almost always resulted in the secure identification of a host galaxy, and this is the first case in which the line of sight is not obscured by the Galactic disc. The dispersion measure of this burst, DMFRB = 1233.696 ± 0.006 pc cm−3, allows for a large source redshift of z > 1 according to the Macquart relation. It could thus be that the host galaxy is consistent with the known population of FRB hosts, but is too distant to detect in our observations (z > 0.7 for a host like that of the first repeating FRB source, FRB 20121102A); that it is more nearby with a significant excess in DMhost, and thus dimmer than any known FRB host; or, least likely, that the FRB is truly hostless. We consider each possibility, making use of the population of known FRB hosts to frame each scenario. The fact of the missing host has ramifications for the FRB field: even with high-precision localization and deep follow-up, some FRB hosts may be difficult to detect, with more distant hosts being the less likely to be found. This has implications for FRB cosmology, in which high-redshift detections are valuable. [ABSTRACT FROM AUTHOR]

We investigate the impact of environment on the internal mass distribution of galaxies using the Middle Ages Galaxy Properties with Integral field spectroscopy (MAGPI) survey. We use 2D resolved stellar kinematics to construct Jeans dynamical models for galaxies at mean redshift z ∼ 0.3, corresponding to a lookback time of 3–4 Gyr. The internal mass distribution for each galaxy is parametrized by the combined mass density slope γ (baryons + dark matter), which is the logarithmic change of density with radius. We use a MAGPI sample of 28 galaxies from low-to-mid density environments and compare to density slopes derived from galaxies in the high density Frontier Fields clusters in the redshift range 0.29 < z < 0.55, corresponding to a lookback time of ∼5 Gyr. We find a median density slope of γ = −2.22 ± 0.05 for the MAGPI sample, which is significantly steeper than the Frontier Fields median slope (γ = −2.00 ± 0.04), implying the cluster galaxies are less centrally concentrated in their mass distribution than MAGPI galaxies. We also compare to the distribution of density slopes from galaxies in ATLAS3D at z ∼ 0, because the sample probes a similar environmental range as MAGPI. The ATLAS3D median total slope is γ = −2.25 ± 0.02, consistent with the MAGPI median. Our results indicate environment plays a role in the internal mass distribution of galaxies, with no evolution of the slope in the last 3–4 Gyr. These results are in agreement with the predictions of cosmological simulations. [ABSTRACT FROM AUTHOR]

In this work, we investigate how the central stellar metallicity ([Z/H]) of 1363 galaxies from the SAMI galaxy survey is related to their stellar mass and a proxy for the gravitational potential, |$\Phi = \log _{10}\left(\frac{M_*}{M_{\odot }} \right) - \log _{10}\left(\frac{r_e}{\mathrm{kpc}} \right)$|⁠. In agreement with previous studies, we find that passive and star-forming galaxies occupy different areas of the [Z/H]– M * plane, with passive galaxies having higher [Z/H] than star-forming galaxies at fixed mass (a difference of 0.23 dex at log10(M */M⊙) = 10.3). We show for the first time that all galaxies lie on the same relation between [Z/H] and Φ, and show that the offset in [Z/H] between passive and star-forming galaxies at fixed Φ is smaller than or equal to the offset in [Z/H] at fixed mass (an average Δ[Z/H] of 0.11 dex at fixed Φ compared to 0.21 dex at fixed mass). We then build a simple model of galaxy evolution to explain and understand our results. By assuming that [Z/H] traces Φ over cosmic time and that the probability that a galaxy quenches depends on both its mass and size, we are able to reproduce these offsets in stellar metallicity with a model containing instantaneous quenching. We therefore conclude that an offset in metallicity at fixed mass cannot by itself be used as evidence of slow quenching processes, in contrast to previous studies. Instead, our model implies that metal-rich galaxies have always been the smallest objects for their mass in a population. Our findings reiterate the need to consider galaxy size when studying stellar populations. [ABSTRACT FROM AUTHOR]

We have used Hubble Space Telescope (HST) images, SAURON Integral Field Spectroscopy (IFS), and adaptative optics assisted Gemini NIFS near-infrared K-band IFS to map the stellar and gas distribution, excitation and kinematics of the inner few kpc of the nearby edge-on S0 galaxy NGC 4111. The HST images map its ≈450 pc diameter dusty polar ring, with an estimated gas mass ≥107 M⊙. The NIFS data cube maps the inner 110 pc radius at ≈7 pc spatial resolution, revealing a ≈220 pc diameter polar ring in hot (2267 ± 166 K) molecular H2 1–0 S(1) gas embedded in the polar ring. The stellar velocity field shows disc-dominated kinematics along the galaxy plane both in the SAURON large scale and in the NIFS nuclear-scale data. The large-scale [O  iii ] λ5007 Å velocity field shows a superposition of two disc kinematics: one similar to that of the stars and another along the polar ring, showing non-circular motions that seem to connect with the velocity field of the nuclear H2 ring, whose kinematics indicate accelerated inflow to the nucleus. The estimated mass inflow rate is enough not only to feed an active galactic nucleus (AGN) but also to trigger circumnuclear star formation in the near future. We propose a scenario in which gas from the polar ring, which probably originated from the capture of a dwarf galaxy, is moving inwards and triggering an AGN, as supported by the local X-ray emission, which seems to be the source of the H2 1–0 S(1) excitation. The fact that we see neither near-UV nor Br γ emission suggests that the nascent AGN is still deeply buried under the optically thick dust of the polar ring. [ABSTRACT FROM AUTHOR]

The change of the total mass density slope, γ, of early-type galaxies through cosmic time is a probe of evolutionary pathways. Hydrodynamical cosmological simulations show that at high redshifts density profiles of early-type galaxies were on average steep (γ ∼ −3). As redshift approaches zero, gas-poor mergers progressively cause the total mass density slope to approach the 'isothermal' slope of γ ∼ −2. Simulations therefore predict steep density slopes at high redshifts, with little to no evolution in density slopes below z ∼ 1. Gravitational lensing results in the same redshift range find the opposite, namely a significant trend of shallow density slopes at high redshifts, becoming steeper as redshift approaches zero. Gravitational lensing results indicate a different evolutionary mechanism for early-type galaxies than dry merging, such as continued gas accretion or off-axis mergers. At redshift zero, isothermal solutions are obtained by both simulations and dynamical modelling. This work applies the Jeans dynamical modelling technique to observations of galaxies at intermediate redshifts (0.29 < z < 0.55) in order to derive density slopes to address the tension between observations and simulations. We combine two-dimensional kinematic fields from Multi Unit Spectroscopic Explorer data with Hubble Space Telescope photometry. The density slopes of 90 early-type galaxies from the Frontier Fields project are presented. The total sample has a median of γ = −2.11 ± 0.03  (standard error), in agreement with dynamical modelling studies at redshift zero. The lack of evolution in total density slopes in the past 4–6 Gyr supports a dry merging model for early-type galaxy evolution. [ABSTRACT FROM AUTHOR]

We present spatially resolved two-dimensional maps and radial trends of the stellar populations and kinematics for a sample of six compact elliptical galaxies (cE) using spectroscopy from the Keck Cosmic Web Imager (KCWI). We recover their star formation histories, finding that all except one of our cEs are old and metal rich, with both age and metallicity decreasing toward their outer radii. We also use the integrated values within one effective radius to study different scaling relations. Comparing our cEs with others from the literature and from simulations we reveal the formation channel that these galaxies might have followed. All our cEs are fast rotators, with relatively high rotation values given their low ellipticites. In general, the properties of our cEs are very similar to those seen in the cores of more massive galaxies, and in particular, to massive compact galaxies. Five out of our six cEs are the result of stripping a more massive (compact or extended) galaxy, and only one cE is compatible with having been formed intrinsically as the low-mass compact object that we see today. These results further confirm that cEs are a mixed-bag of galaxies that can be formed following different formation channels, reporting for the first time an evolutionary link within the realm of compact galaxies (at all stellar masses). [ABSTRACT FROM AUTHOR]

We present population-orbit superposition models for external galaxies based on Schwarzschild's orbit-superposition method, by tagging the orbits with age and metallicity. The models fit the density distributions, kinematic, and age and metallicity maps from integral field unit (IFU) spectroscopy observations. We validate the method and demonstrate its power by applying it to mock data, similar to those obtained by the Multi-Unit Spectroscopic Explorer (MUSE) IFU on the Very Large Telescope (VLT). These mock data are created from Auriga galaxy simulations, viewed at three different inclination angles (ϑ = 40°, 60°, 80°). Constrained by MUSE-like mock data, our model can recover the galaxy's stellar orbit distribution projected in orbital circularity λ z versus radius r , the intrinsic stellar population distribution in age t versus metallicity Z , and the correlation between orbits' circularity λ z and stellar age t. A physically motivated age–metallicity relation improves the recovering of intrinsic stellar population distributions. We decompose galaxies into cold, warm, and hot+counter-rotating components based on their orbit circularity distribution, and find that the surface density, velocity, velocity dispersion, and age and metallicity maps of each component from our models well reproduce those from simulation, especially for projections close to edge-on. These galaxies exhibit strong global age versus σ z relation, which is well recovered by our model. The method has the power to reveal the detailed build-up of stellar structures in galaxies, and offers a complement to local resolved, and high-redshift studies of galaxy evolution. [ABSTRACT FROM AUTHOR]

We study a sample of 148 early-type galaxies in the Coma cluster using SDSS photometry and spectra, and calibrate our results using detailed dynamical models for a subset of these galaxies, to create a precise benchmark for dynamical scaling relations in high-density environments. For these galaxies, we successfully measured global galaxy properties, modelled stellar populations, and created dynamical models, and support the results using detailed dynamical models of 16 galaxies, including the two most massive cluster galaxies, using data taken with the SAURON IFU. By design, the study provides minimal scatter in derived scaling relations due to the small uncertainty in the relative distances of galaxies compared to the cluster distance. Our results demonstrate low (≤55 per cent for 90th percentile) dark matter fractions in the inner 1 R e of galaxies. Owing to the study design, we produce the tightest, to our knowledge, IMF–σe relation of galaxies, with a slope consistent with that seen in local galaxies. Leveraging our dynamical models, we transform the classical Fundamental Plane of the galaxies to the Mass Plane. We find that the coefficients of the Mass Plane are close to predictions from the virial theorem, and have significantly lower scatter compared to the Fundamental Plane. We show that Coma galaxies occupy similar locations in the (M *– R e) and (M *−σe) relations as local field galaxies but are older. This, and the fact we find only three slow rotators in the cluster, is consistent with the scenario of hierarchical galaxy formation and expectations of the kinematic morphology–density relation. [ABSTRACT FROM AUTHOR]

We present a combination of the Schwarzschild orbit-superposition dynamical modelling technique with the spatially resolved mean stellar age and metallicity maps to uncover the formation history of galaxies. We apply this new approach to a remarkable five-pointing mosaic of VLT/MUSE observations obtained by Guérou et al. (2016) extending to a maximum galactocentric distance of |${\sim } {120}{\, {\rm arcsec}}\ \left({5.6}\, {\rm kpc}\right)$| along the major axis, corresponding to ∼2.5 R e. Our method first identifies 'families' of orbits from the dynamical model that represent dynamically distinct structures of the galaxy. Individual ages and metallicities of these components are then fit for using the stellar-population information. Our results highlight components of the galaxy that are distinct in the combined stellar dynamics/populations space, which implies distinct formation paths. We find evidence for a dynamically cold, metal-rich disc, consistent with a gradual in situ formation. This disc is embedded in a generally old population of stars, with kinematics ranging from dispersion dominated in the centre to an old, diffuse, metal-poor stellar halo at the extremities. We find also a direct correlation between the dominant dynamical support of these components, and their associated age, akin to the relation observed in the Milky Way. This approach not only provides a powerful model for inferring the formation history of external galaxies but also paves the way to a complete population-dynamical model. [ABSTRACT FROM AUTHOR]

We present mass estimates of supermassive black holes in six nearby fast rotating early-type galaxies (NGC 4339, NGC 4434, NGC 4474, NGC 4551, NGC 4578, and NGC 4762) with effective stellar velocity dispersion around 100 km s−1. We use near-infrared laser-guide adaptive optics observations with the GEMINI/NIFS to derive stellar kinematics in the galactic nuclei, and SAURON observations from the atlas3D Survey for large-scale kinematics. We build axisymmetric Jeans anisotropic models and axisymmetric Schwarzschild dynamical models. Both modelling approaches recover consistent orbital anisotropies and black hole masses within 1σ–2σ confidence level, except for one galaxy for which the difference is just above the 3σ level. Two black holes (NGC 4339 and NGC 4434) are amongst the largest outliers from the current black hole mass–velocity dispersion relation, with masses of $(4.3^{+4.8}_{-2.3})\times 10^7$ and $(7.0^{+2.0}_{-2.8})\times 10^7$ M⊙, respectively (3σ confidence level). The black holes in NGC 4578 and NGC 4762 lie on the scaling relation with masses of $(1.9^{+0.6}_{-1.4})\times 10^7$ and $(2.3^{+0.9}_{-0.6})\times 10^7$ M⊙, respectively (3σ confidence level). For two galaxies (NGC 4474 and NGC 4551), we are able to place upper limits on their black holes masses (<7 × 106 and <5 × 106 M⊙, respectively, 3σ confidence level). The kinematics for these galaxies clearly indicate central velocity dispersion drops within a radius of 35 and 80 pc, respectively. These drops cannot be associated with cold stellar structures and our data do not have the resolution to exclude black holes with masses an order of magnitude smaller than the predictions. Parametrizing the orbital distribution in spherical coordinates, the vicinity of the black holes is characterized by isotropic or mildly tangential anisotropy. [ABSTRACT FROM AUTHOR]

We present the first major release of data from the SAMI Galaxy Survey. This data release focuses on the emission-line physics of galaxies. Data Release One includes data for 772 galaxies, about 20 per cent of the full survey. Galaxies included have the redshift range 0.004 < z < 0.092, a large mass range (7.6 < logM*/M☉ < 11.6), and star formation rates of ∼10-4 to ∼101M☉ yr-1. For each galaxy, we include two spectral cubes and a set of spatially resolved 2D maps: single- and multi-component emission-line fits (with dust-extinction corrections for strong lines), local dust extinction, and star formation rate. Calibration of the fibre throughputs, fluxes, and differential atmospheric refraction has been improved over the Early Data Release. The data have average spatial resolution of 2.16 arcsec (full width at half-maximum) over the 15 arcsec diameter field of view and spectral (kinematic) resolution of R = 4263 (σ = 30 km s-1) around Hα. The relative flux calibration is better than 5 per cent, and absolute flux calibration has an rms of 10 per cent. The data are presented online through the Australian Astronomical Observatory's Data Central. [ABSTRACT FROM AUTHOR]

We present the WiFeS Atlas of Galactic Globular cluster Spectra, a library of integrated spectra of Milky Way and Local Group globular clusters. We used the WiFeS integral field spectrograph on the Australian National University 2.3 m telescope to observe the central regions of 64 MilkyWay globular clusters and 22 globular clusters hosted by the MilkyWay's low-mass satellite galaxies. The spectra have wider wavelength coverage (3300-9050 Å) and higher spectral resolution (R = 6800) than existing spectral libraries of Milky Way globular clusters. By including Large and SmallMagellanic Cloud star clusters, we extend the coverage of parameter space of existing libraries towards young and intermediate ages. While testing stellar population synthesis models and analysis techniques is the main aim of this library, the observations may also further our understanding of the stellar populations of Local Group globular clusters and make possible the direct comparison of extragalactic globular cluster integrated light observations with well-understood globular clusters in the Milky Way. The integrated spectra are publicly available via the project website. [ABSTRACT FROM AUTHOR]

We study trends in the slope of the total mass profiles and dark matter fractions within the central half-light radius of 258 early-type galaxies, using data from the volume-limited ATLAS3D survey.We use three distinct sets of dynamical models, which vary in their assumptions and also allow for spatial variations in the stellarmass-to-light ratio, to test the robustness of our results. We confirm that the slopes of the total mass profiles are approximately isothermal, and investigate how the total mass slope depends on various galactic properties. The most statistically significant correlations we find are a function of either surface density, ∑e, or velocity dispersion, σe. However there is evidence for a break in the latter relation, with a nearly universal logarithmic slope above log10[σe/(km s-1)] ∼ 2.1 and a steeper trend below this value. For the 142 galaxies above that critical σe value, the total mass-density logarithmic slopes have a mean value ≺γ1 ≻ = -2.193 ± 0.016 (1σ error) with an observed rms scatter of only σγ1 = 0.168 ± 0.015. Considering the observational errors, we estimate an intrinsic scatter of #8230;.These values are broadly consistent with those found by strong lensing studies at similar radii and agree, within the tight errors, with values recently found at much larger radii via stellar dynamics or H I rotation curves (using significantly smaller samples than this work). [ABSTRACT FROM AUTHOR]

We here present the first spatially resolved study of the initial mass function (IMF) in external galaxies derived using a dynamical tracer of the mass-to-light ratio (M/L). We use the kinematics of relaxed molecular gas discs in seven early-type galaxies (ETGs) selected from the ATLAS3D survey to dynamically determine M/L gradients. These M/L gradients are not very strong in the inner parts of these objects, and galaxies that do show variations are those with the highest specific star formation rates. Stellar population parameters derived from star formation histories are then used in order to estimate the stellar IMF mismatch parameter, and shed light on its variation within ETGs. Some of our target objects require a light IMF, otherwise their stellar population masses would be greater than their dynamical masses. In contrast, other systems seem to require heavier IMFs to explain their gas kinematics. Our analysis again confirms that IMF variation seems to be occurring within massive ETGs. We find good agreement between our IMF normalizations derived using molecular gas kinematics and those derived using other techniques. Despite this, we do not see find any correlation between the IMF normalization and galaxy dynamical properties or stellar population parameters, either locally or globally. In the future, larger studies which use molecules as tracers of galaxy dynamics can be used to help us disentangle the root cause of IMF variation. [ABSTRACT FROM AUTHOR]

We present a 1.4 GHz Karl G. Jansky Very Large Array (VLA) study of a sample of early-type galaxies (ETGs) from the ATLASeD survey. The radio morphologies of these ETGs at a resolution of ϑFWHM ≈ 5 arc sec include sources that are compact on sub-kpc scales, resolved structures similar to those seen in star-forming spiral galaxies, and kpc-scale radio jets/lobes associated with active nuclei. We compare the radio, CO, and infrared (IR) properties of these ETGs. The most CO-rich ETGs have radio luminosities consistent with extrapolations from H2 mass derived star-formation rates from studies of late-type galaxies. These ETGs also follow the radio-IR correlation. However, ETGs with lower molecular gas masses tend to have less radio emission relative to their CO and IR emission compared to spirals. The fraction of galaxies in our sample with high IR-radio ratios is much higher than in previous studies, and cannot be explained by a systematic underestimation of the radio luminosity due to the presence extended, low-surface-brightness emission that was resolved out in our VLA observations. We find that the high IR-radio ratios tend to occur at low IR luminosities, but are not associated with low dynamical mass or metallicity. Thus, we have identified a population of ETGs that have a genuine shortfall of radio emission relative to both their IR and CO emission. A number of mechanisms may cause this deficiency, including a bottom-heavy stellar initial mass function, weak magnetic fields, a higher prevalence of environmental effects compared to spirals, and enhanced cosmic ray losses. [ABSTRACT FROM AUTHOR]

We present the results of a high-resolution, 5 GHz, Karl G. Jansky Very Large Array study of the nuclear radio emission in a representative subset of the ATLAS3D survey of early-type galaxies (ETGs). We find that 51 ± 4 per cent of the ETGs in our sample contain nuclear radio emission with luminosities as low as 1018 W Hz-1. Most of the nuclear radio sources have compact (≲25-110 pc) morphologies, although ~10 per cent display multicomponent core+jet or extended jet/lobe structures. Based on the radio continuum properties, as well as optical emission line diagnostics and the nuclear X-ray properties, we conclude that the majority of the central 5 GHz sources detected in the ATLAS3D galaxies are associated with the presence of an active galactic nucleus (AGN). However, even at subarcsecond spatial resolution, the nuclear radio emission in some cases appears to arise from low-level nuclear star formation rather than an AGN, particularly when molecular gas and a young central stellar population is present. This is in contrast to popular assumptions in the literature that the presence of a compact, unresolved, nuclear radio continuum source universally signifies the presence of an AGN. Additionally, we examine the relationships between the 5 GHz luminosity and various galaxy properties including the molecular gas mass and-for the first time - the global kinematic state. We discuss implications for the growth, triggering, and fuelling of radio AGNs, as well as AGN-driven feedback in the continued evolution of nearby ETGs. [ABSTRACT FROM AUTHOR]

We analyse the stellar absorption features in high signal-to-noise ratio (S/N) near-infrared (NIR) spectra of the nuclear region of 12 nearby galaxies, mostly spirals. The features detected in some or all of the galaxies in this sample are the TiO (0.843 and 0.886 μm), VO (1.048 μm), CN (1.1 and 1.4 μm), H2O (1.4 and 1.9 μm) and CO (1.6 and 2.3 μm) bands. The C2 (1.17 and 1.76 μm) bands are generally weak or absent, although C2 (1.76 μm) may be weakly present in the mean galaxy spectrum. A deep feature near 0.93 μm, likely caused by CN, TiO and/or ZrO, is also detected in all objects. Fitting a combination of stellar spectra to the mean spectrum shows that the absorption features are produced by evolved stars: cool giants and supergiant stars in the early- or thermally pulsing asymptotic giant branch (E-AGB or TP-AGB) phases. The high luminosity of TP-AGB stars, and the appearance of VO and ZrO features in the data, suggest that TP-AGB stars dominate these spectral features. However, a contribution from other evolved stars is also likely. Comparison with evolutionary population synthesis models shows that models based on empirical libraries that predict relatively strong NIR features provide a more accurate description of the data. However, none of the models tested accurately reproduces all of the features observed in the spectra. To do so, the models will need to not only improve the treatment of TP-AGB stars, but also include good quality spectra of red giant and E-AGB stars. The uninterrupted wavelength coverage, high S/N and quantity of features we present here will provide a benchmark for the next generation of models aiming to explain and predict the NIR properties of galaxies. [ABSTRACT FROM AUTHOR]

We analyse the spatially resolved stellar populations of nine local (z < 0.1) Brightest Cluster Galaxies (BCGs) observed with VIMOS in Integral Field Unit mode. Our sample is composed of seven slow-rotating and two fast-rotating BCGs. We do not find a connection between stellar kinematics and stellar populations in this small sample. The BCGs have shallow metallicity gradients (median Δ[Fe/H]=-0.11 ± 0.1), high central metallicities (median [Fe/H][α/Fe] = 0 = 0.13 ± 0.07), and a wide range of central ages (from 5 to 15 Gyr). We propose that the reason for this is diverse evolutionary paths in BCGs. 67 per cent of the sample (6/9) show ~7 Gyr old central ages, which reflects an active accretion history, and 33 per cent of the sample (3/9) have central ages older than 11 Gyr, which suggest no star formation since z = 2. The BCGs show similar central stellar populations and stellar population gradients to early-type galaxies of similar mass (Mdyn > 1011.3 M☉) from the ATLAS3D survey (median [Z/H] = 0.04 ± 0.07, Δ[Z/H] = -0.19 ± 0.1). However, massive early-type galaxies from ATLAS3D have consistently old ages (median Age = 12.0 ± 3.8 Gyr). We also analyse the close massive companion galaxies of two of the BCGs. These galaxies have similar stellar populations to their respective BCGs. [ABSTRACT FROM AUTHOR]

We present the stellar population content of early-type galaxies from the ATLAS3D survey. Using spectra integrated within apertures covering up to one effective radius, we apply two methods: one based on measuring line-strength indices and applying single stellar population (SSP) models to derive SSP-equivalent values of stellar age, metallicity, and alpha enhancement; and one based on spectral fitting to derive non-parametric star formation histories, mass-weighted average values of age, metallicity, and half-mass formation time-scales. Using homogeneously derived effective radii and dynamically determined galaxy masses, we present the distribution of stellar population parameters on the Mass Plane (MJAM, σe, Rmaje), showing that at fixed mass, compact early-type galaxies are on average older, more metal-rich, and more alpha-enhanced than their larger counterparts. From non-parametric star formation histories, we find that the duration of star formation is systematically more extended in lower mass objects. Assuming that our sample represents most of the stellar content of today's local Universe, approximately 50 per cent of all stars formed within the first 2 Gyr following the big bang. Most of these stars reside today in the most massive galaxies (>1010.5 M⊙), which themselves formed 90 per cent of their stars by z ~ 2. The lower mass objects, in contrast, have formed barely half their stars in this time interval. Stellar population properties are independent of environment over two orders of magnitude in local density, varying only with galaxy mass. In the highest density regions of our volume (dominated by the Virgo cluster), galaxies are older, alpha-enhanced, and have shorter star formation histories with respect to lower density regions. [ABSTRACT FROM AUTHOR]

Galactic archaeology based on star counts is instrumental to reconstruct the past mass assembly of Local Group galaxies. The development of new observing techniques and data reduction, coupled with the use of sensitive large field of view cameras, now allows us to pursue this technique in more distant galaxies exploiting their diffuse low surface brightness (LSB) light. As part of the ATLAS3D project, we have obtained with the MegaCam camera at the Canada–France–Hawaii Telescope extremely deep, multiband images of nearby early-type galaxies (ETGs). We present here a catalogue of 92 galaxies from the ATLAS3D sample, which are located in low- to medium-density environments. The observing strategy and data reduction pipeline, which achieve a gain of several magnitudes in the limiting surface brightness with respect to classical imaging surveys, are presented. The size and depth of the survey are compared to other recent deep imaging projects. The paper highlights the capability of LSB-optimized surveys at detecting new prominent structures that change the apparent morphology of galaxies. The intrinsic limitations of deep imaging observations are also discussed, among those, the contamination of the stellar haloes of galaxies by extended ghost reflections, and the cirrus emission from Galactic dust. The detection and systematic census of fine structures that trace the present and past mass assembly of ETGs are one of the prime goals of the project. We provide specific examples of each type of observed structures – tidal tails, stellar streams and shells – and explain how they were identified and classified. We give an overview of the initial results. The detailed statistical analysis will be presented in future papers. [ABSTRACT FROM AUTHOR]

We use the ATLAS3D sample to perform a study of the intrinsic shapes of early-type galaxies, taking advantage of the available combined photometric and kinematic data. Based on our ellipticity measurements from the Sloan Digital Sky Survey Data Release 7, and additional imaging from the Isaac Newton Telescope, we first invert the shape distribution of fast and slow rotators under the assumption of axisymmetry. The so-obtained intrinsic shape distribution for the fast rotators can be described with a Gaussian with a mean flattening of q = 0.25 and standard deviation σq = 0.14, and an additional tail towards rounder shapes. The slow rotators are much rounder, and are well described with a Gaussian with mean q = 0.63 and σq = 0.09. We then checked that our results were consistent when applying a different and independent method to obtain intrinsic shape distributions, by fitting the observed ellipticity distributions directly using Gaussian parametrizations for the intrinsic axis ratios. Although both fast and slow rotators are identified as early-type galaxies in morphological studies, and in many previous shape studies are therefore grouped together, their shape distributions are significantly different, hinting at different formation scenarios. The intrinsic shape distribution of the fast rotators shows similarities with the spiral galaxy population. Including the observed kinematic misalignment in our intrinsic shape study shows that the fast rotators are predominantly axisymmetric, with only very little room for triaxiality. For the slow rotators though there are very strong indications that they are (mildly) triaxial. [ABSTRACT FROM AUTHOR]

We present a study of the cold gas contents of the Atlas3D early-type galaxies, in the context of their optical colours, near-ultraviolet colours and Hβ absorption line strengths. Early-type (elliptical and lenticular) galaxies are not as gas poor as previously thought, and at least 40 per cent of local early-type galaxies are now known to contain molecular and/or atomic gas. This cold gas offers the opportunity to study recent galaxy evolution through the processes of cold gas acquisition, consumption (star formation) and removal. Molecular and atomic gas detection rates range from 10 to 34 per cent in red sequence early-type galaxies, depending on how the red sequence is defined, and from 50 to 70 per cent in blue early-type galaxies. Notably, massive red sequence early-type galaxies (stellar masses >5 × 1010 M⊙, derived from dynamical models) are found to have H i masses up to M(H i)/M* ∼ 0.06 and H2 masses up to M(H2)/M* ∼ 0.01. Some 20 per cent of all massive early-type galaxies may have retained atomic and/or molecular gas through their transition to the red sequence. However, kinematic and metallicity signatures of external gas accretion (either from satellite galaxies or the intergalactic medium) are also common, particularly at stellar masses ≤5 × 1010 M⊙, where such signatures are found in ∼50 per cent of H2-rich early-type galaxies. Our data are thus consistent with a scenario in which fast rotator early-type galaxies are quenched former spiral galaxies which have undergone some bulge growth processes, and in addition, some of them also experience cold gas accretion which can initiate a period of modest star formation activity. We discuss implications for the interpretation of colour–magnitude diagrams. [ABSTRACT FROM AUTHOR]

We present measurements of the star formation rate (SFR) in the early-type galaxies (ETGs) of the ATLAS3D sample, based on Wide-field Infrared Survey Explorer (WISE) 22 μm and Galaxy Evolution Explorer far-ultraviolet emission. We combine these with gas masses estimated from 12CO and H i data in order to investigate the star formation efficiency (SFE) in a larger sample of ETGs than previously available. We first recalibrate (based on WISE data) the relation between old stellar populations (traced at Ks band) and 22 μm luminosity, allowing us to remove the contribution of 22 μm emission from circumstellar dust. We then go on to investigate the position of ETGs on the Kennicutt–Schmidt (KS) relation. Molecular gas-rich ETGs have comparable star formation surface densities to normal spiral galaxy centres, but they lie systematically offset from the KS relation, having lower SFEs by a factor of ≈2.5 (in agreement with other authors). This effect is driven by galaxies where a substantial fraction of the molecular material is in the rising part of the rotation curve, and shear is high. We show here for the first time that although the number of stars formed per unit gas mass per unit time is lower in ETGs, it seems that the amount of stars formed per free-fall time is approximately constant. The scatter around this dynamical relation still correlates with galaxy properties such as the shape of the potential in the inner regions. This leads us to suggest that dynamical properties (such as shear or the global stability of the gas) may be important second parameters that regulate star formation and cause much of the scatter around star formation relations. [ABSTRACT FROM AUTHOR]

We use interferometric 12CO(1–0) observations to compare and contrast the extent, surface brightness profiles and kinematics of the molecular gas in CO-rich ATLAS3D early-type galaxies (ETGs) and spiral galaxies. We find that the molecular gas extent is smaller in absolute terms in ETGs than in late-type galaxies, but that the size distributions are similar once scaled by the galaxies optical/stellar characteristic scalelengths. Amongst ETGs, we find that the extent of the gas is independent of its kinematic misalignment (with respect to the stars), but does depend on the environment, with Virgo cluster ETGs having less extended molecular gas reservoirs, further emphasizing that cluster ETGs follow different evolutionary pathways from those in the field. Approximately half of ETGs have molecular gas surface brightness profiles that follow the stellar light profile. These systems often have relaxed gas out to large radii, suggesting they are unlikely to have had recent merger/accretion events. A third of the sample galaxies show molecular gas surface brightness profiles that fall off slower than the light, and sometimes show a truncation. These galaxies often have a low mass, and either have disturbed molecular gas or are in the Virgo cluster, suggesting that recent mergers, ram pressure stripping and/or the presence of hot gas can compress/truncate the gas. The remaining galaxies have rings, or composite profiles, that we argue can be caused by the effects of bars. We investigated the kinematics of the molecular gas using position–velocity diagrams, and compared the observed kinematics with dynamical model predictions, and the observed stellar and ionized gas velocities. We confirm that the molecular gas reaches beyond the turnover of the circular velocity curve in ≈70 per cent of our CO-rich ATLAS3D ETGs, validating previous work on the CO Tully–Fisher relation. In general we find that in most galaxies the molecular gas is dynamically cold, and the observed CO rotation matches well model predictions of the circular velocity. In the galaxies with the largest molecular masses, dust obscuration and/or population gradients can cause model predictions of the circular velocity to disagree with observations of the molecular gas rotation; however, these effects are confined to the most star forming systems. Bars and non-equilibrium conditions can also make the gas deviate from circular orbits. In both these cases, one expects the model circular velocity to be higher than the observed CO velocity, in agreement with our observations. Molecular gas is a better direct tracer of the circular velocity than the ionized gas, justifying its use as a kinematic tracer for Tully–Fisher and similar analyses. [ABSTRACT FROM AUTHOR]

We report the discovery of a giant HI tail in the intragroup medium of HCG 44 as part of the ATLAS3D survey. The tail is ~300 kpc long in projection and contains ~5 × 108 M⊙ of HI. We detect no diffuse stellar light at the location of the tail down to ~28.5 mag arcsec-2 in g band. We speculate that the tail might have formed as gas was stripped from the outer regions of NGC 3187 (a member of HCG 44) by the group tidal field. In this case, a simple model indicates that about 1/3 of the galaxy's HI was stripped during a time interval of <1 Gyr. Alternatively, the tail may be the remnant of an interaction between HCG 44 and NGC 3162, a spiral galaxy now ~650 kpc away from the group. Regardless of the precise formation mechanism, the detected HI tail shows for the first time direct evidence of gas stripping in HCG 44. It also highlights that deep HI observations over a large field are needed to gather a complete census of this kind of events in the local Universe. [ABSTRACT FROM AUTHOR]

We report the discovery of a giant H i tail in the intragroup medium of HCG 44 as part of the ATLAS3D survey. The tail is ∼ 300 kpc long in projection and contains ∼ 5 × 108 M⊙ of H i. We detect no diffuse stellar light at the location of the tail down to ∼ 28.5 mag arcsec− 2 in g band. We speculate that the tail might have formed as gas was stripped from the outer regions of NGC 3187 (a member of HCG 44) by the group tidal field. In this case, a simple model indicates that about 1/3 of the galaxy's H i was stripped during a time interval of < 1 Gyr. Alternatively, the tail may be the remnant of an interaction between HCG 44 and NGC 3162, a spiral galaxy now ∼ 650 kpc away from the group. Regardless of the precise formation mechanism, the detected H i tail shows for the first time direct evidence of gas stripping in HCG 44. It also highlights that deep H i observations over a large field are needed to gather a complete census of this kind of events in the local Universe. [ABSTRACT FROM PUBLISHER]

ABSTRACT We use the Spectrographic Areal Unit for Research on Optical Nebulae and Gemini Multi-Object Spectrograph integral-field spectrographs to observe the active galactic nucleus (AGN) powered outflow in NGC 1266. This unusual galaxy is relatively nearby ( D = 30 Mpc), allowing us to investigate the process of AGN feedback in action. We present maps of the kinematics and line strengths of the ionized gas emission lines Hα, Hβ, [O iii], [O i], [N ii] and [S ii], and report on the detection of sodium D absorption. We use these tracers to explore the structure of the source, derive the ionized and atomic gas kinematics, and investigate the gas excitation and physical conditions. NGC 1266 contains two ionized gas components along most lines of sight, tracing the ongoing outflow and a component closer to the galaxy systemic, the origin of which is unclear. This gas appears to be disturbed by a nascent AGN jet. We confirm that the outflow in NGC 1266 is truly multiphase, containing radio plasma, atomic, molecular and ionized gas and X-ray emitting plasma. The outflow has velocities of up to ±900 km s−1 away from the systemic velocity and is very likely to remove significant amount of cold gas from the galaxy. The low-ionization nuclear emission region-like line emission in NGC 1266 is extended, and it likely arises from fast shocks caused by the interaction of the radio jet with the interstellar medium. These shocks have velocities of up to 800 km s−1, which match well with the observed velocity of the outflow. Sodium D equivalent width profiles are used to set constraints on the size and orientation of the outflow. The ionized gas morphology correlates with the nascent radio jets observed in 1.4 and 5 GHz continuum emission, supporting the suggestion that an AGN jet is providing the energy required to drive the outflow. [ABSTRACT FROM AUTHOR]

ABSTRACT We investigate the accuracy in the recovery of the stellar dynamics of barred galaxies when using axisymmetric dynamical models. We do this by trying to recover the mass-to-light ratio ( M/ L) and the anisotropy of realistic galaxy simulations using the Jeans Anisotropic Multi-Gaussian Expansion (JAM) modelling method. However, given that the biases we find are mostly due to an application of an axisymmetric modelling algorithm to a non-axisymmetric system and in particular to inaccuracies in the deprojected mass model, our results are relevant for general axisymmetric modelling methods. We run N-body collisionless simulations to build a library with various luminosity distribution, constructed to mimic real individual galaxies, with realistic anisotropy. The final result of our evolved library of simulations contains both barred and unbarred galaxies. The JAM method assumes an axisymmetric mass distribution, and we adopt a spatially constant M/ L and anisotropy distributions. The models are fitted to two-dimensional maps of the second velocity moments of the simulations for various viewing angles [position angle (PA) of the bar and inclination of the galaxy]. We find that the inclination is generally well recovered by the JAM models, for both barred and unbarred simulations. For unbarred simulations the M/ L is also accurately recovered, with negligible median bias and with a maximum one of just Δ( M/ L) < 1.5 per cent when the galaxy is not too close to face on. At very low inclinations () the M/ L can be significantly overestimated (9 per cent in our tests, but errors can be larger for very face-on views). This is in agreement with previous studies. For barred simulations the M/ L is on average (when PA = 45°) essentially unbiased, but we measure an over/underestimation of up to Δ( M/ L) = 15 per cent in our tests. The sign of the M/ L bias depends on the PA of the bar as expected: overestimation occurs when the bar is closer to end-on, due to the increased stellar motion along the line-of-sight, and underestimation otherwise. For unbarred simulations, the JAM models are able to recover the mean value of the anisotropy with bias , within the region constrained by the kinematics. However when a bar is present, or for nearly face-on models, the recovered anisotropy varies wildly, with biases up to Δβ z≈ 0.3. [ABSTRACT FROM AUTHOR]

ABSTRACT The unexpected rising flux of early-type galaxies at decreasing ultraviolet (UV) wavelengths is a long-standing mystery. One important observational constraint is the correlation between UV-optical colours and Mg2 line strengths found by Burstein et al. The simplest interpretation of this phenomenon is that the UV strength is related to the Mg line strength. Under this assumption, we expect galaxies with larger Mg gradients to have larger UV colour gradients. By combining UV imaging from GALEX, optical imaging from MDM and SAURON integral-field spectroscopy, we investigate the spatially resolved relationships between UV colours and stellar population properties of 34 early-type galaxies from the SAURON survey sample. We find that galaxies with old stellar populations show tight correlations between the far-UV (FUV) colours (FUV − V and FUV − NUV) and the Mg b index, Hβ index and metallicity [ Z/H]. The equivalent correlations for the Fe5015 index, α-enhancement [α/Fe] and age are present but weaker. We have also derived logarithmic internal radial colour, measured line strength and derived stellar population gradients for each galaxy and again found a strong dependence of the FUV − V and FUV − NUV colour gradients on both the Mg b line strength and the metallicity gradients for galaxies with old stellar populations. In particular, global gradients of Mg b and [ Z/H] with respect to the UV colour [e.g. Δ(Mg b)/Δ(FUV − NUV) and Δ[ Z/H]/Δ(FUV − NUV)] across galaxies are consistent with their local gradients within galaxies, suggesting that the global correlations also hold locally. From a simple model based on multiband colour fits of UV upturn and UV-weak galaxies, we have identified a plausible range of parameters that reproduces the observed radial colour profiles. In these models, the centres of elliptical galaxies, where the UV flux is strong, are enhanced in metals by roughly 60 per cent compared to UV-weak regions. [ABSTRACT FROM AUTHOR]

ABSTRACT We present the ATLAS3D H i survey of a volume-limited, complete sample of 166 nearby early-type galaxies (ETGs) brighter than MK=−21.5. The survey is mostly based on data taken with the Westerbork Synthesis Radio Telescope, which enables us to detect H i down to 5 × 106-5 × 107 M⊙ within the survey volume. We detect ∼40 per cent of all ETGs outside the Virgo galaxy cluster and ∼10 per cent of all ETGs inside it. This demonstrates that it is common for non-cluster ETGs to host H i. The morphology of the detected gas varies in a continuous way from regular, settled H i discs and rings to unsettled gas distributions (including tidal or accretion tails) and systems of clouds scattered around the galaxy. The majority of the detections consist of H i discs or rings (1/4 of all ETGs outside Virgo) so that if H i is detected in an ETG it is most likely distributed on a settled configuration. These systems come in two main types: small discs [ M⊙], which are confined within the stellar body and share the same kinematics of the stars; and large discs/rings [ M(H i) up to 5 × 109 M⊙], which extend to tens of kpc from the host galaxy and are in half of the cases kinematically decoupled from the stars. Neutral hydrogen seems to provide material for star formation in ETGs. Galaxies containing H i within ∼1 Re exhibit signatures of on-going star formation in ∼70 per cent of the cases, approximately five times more frequently than galaxies without central H i. The interstellar medium (ISM) in the centre of these galaxies is dominated by molecular gas, and in ETGs with a small gas disc the conversion of H i into H2 is as efficient as in spirals. The ETG H i mass function is characterized by M*∼ 2 × 109 M⊙ and by a slope α∼−0.7. Compared to spirals, ETGs host much less H i as a family. However, a significant fraction of all ETGs are as H i-rich as spiral galaxies. The main difference between ETGs and spirals is that the former lack the high-column-density H i typical of the bright stellar disc of the latter. The ETG H i properties vary with environment density in a more continuous way than suggested by the known Virgo versus non-Virgo dichotomy. We find an envelope of decreasing M(H i) and M(H i)/ LK with increasing environment density. The gas-richest galaxies live in the poorest environments (as found also with CO observations), where the detection rate of star formation signatures is higher. Galaxies in the centre of Virgo have the lowest H i content, while galaxies at the outskirts of Virgo represent a transition region and can contain significant amounts of H i, indicating that at least a fraction of them has joined the cluster only recently after pre-processing in groups. Finally, we find an H i morphology-density relation such that at low environment density (measured on a local scale) the detected H i is mostly distributed on large, regular discs and rings, while more disturbed H i morphologies dominate environment densities typical of rich groups. This confirms the importance of processes occurring on a galaxy-group scale for the evolution of ETGs. [ABSTRACT FROM AUTHOR]

ABSTRACT Surveying 18 12CO-bright galaxies from the ATLAS3D early-type galaxy sample with the Institut de Radio Astronomie Millimétrique (IRAM) 30-m telescope, we detect 13CO(1-0) and 13CO(2-1) in all 18 galaxies, HCN(1-0) in 12/18 and HCO+(1-0) in 10/18. We find that the line ratios 12CO(1-0)/13CO(1-0) and 12CO(1-0)/HCN(1-0) are clearly correlated with several galaxy properties: total stellar mass, luminosity-weighted mean stellar age, molecular-to-atomic gas ratio, dust temperature and dust morphology. We suggest that these correlations are primarily governed by the optical depth in the 12CO lines; interacting, accreting and/or starbursting early-type galaxies have more optically thin molecular gas while those with settled dust and gas discs host optically thick molecular gas. The ranges of the integrated line intensity ratios generally overlap with those of spirals, although we note some outliers in the 12CO(1-0)/13CO(1-0), 12CO(2-1)/13CO(2-1) and HCN/HCO+(1-0) ratios. In particular, three galaxies are found to have very low 12CO(1-0)/13CO(1-0) and 12CO(2-1)/13CO(2-1) ratios. Such low ratios may signal particularly stable molecular gas which creates stars less efficiently than 'normal' (i.e. below Schmidt-Kennicutt prediction), consistent with the low dust temperatures seen in these galaxies. [ABSTRACT FROM AUTHOR]

ABSTRACT We investigate the [3.6]−[4.5] Spitzer-IRAC colour behaviour of the early-type galaxies of the SAURON survey, a representative sample of 48 nearby ellipticals and lenticulars. We investigate how this colour, which is unaffected by dust extinction, can be used to constrain the stellar populations in these galaxies. We find a tight relation between the [3.6]−[4.5] colour and effective velocity dispersion, a good mass indicator in early-type galaxies: ( [3.6]−[4.5]) e = ( −0.109 0.007)+ (0.154 0.016). Contrary to other colours in the optical and near-infrared, we find that the colours become bluer for larger galaxies. The relations are tighter when using the colour inside re (scatter 0.013 mag), rather than the much smaller re/8 aperture (scatter 0.023 mag), due to the presence of young populations in the central regions. We also obtain strong correlations between the [3.6]−[4.5] colour and three strong absorption lines (H, Mg b and Fe 5015). Comparing our data with the models of Marigo et al., which show that more metal rich galaxies are bluer, we can explain our results in a way consistent with results from the optical, by stating that larger galaxies are more metal rich. The blueing is caused by a strong CO absorption band, whose line strength increases strongly with decreasing temperature and which covers a considerable fraction of the 4.5-m filter. In galaxies that contain a compact radio source, the [3.6]−[4.5] colour is generally slightly redder (by 0.015 0.007 mag using the re/8 aperture) than in the other galaxies, indicating small amounts of either hot dust, non-thermal emission, or young stars near the centre. We find that the large majority of the galaxies show redder colours with increasing radius. Removing the regions with evidence for young stellar populations (from the H absorption line) and interpreting the colour gradients as metallicity gradients, we find that our galaxies are more metal poor going outwards. The radial [3.6]−[4.5] gradients correlate very well with the metallicity gradients derived from optical line indices. We do not find any correlation between the gradients and galaxy mass; at every mass, galaxies display a real range in metallicity gradients. Consistent with our previous work on line indices, we find a tight relation between local [3.6]−[4.5] colour and local escape velocity. The small scatter from galaxy to galaxy, although not negligible, shows that the amount and distribution of the dark matter relative to the visible light cannot be too different from galaxy to galaxy. Due to the lower sensitivity of the [3.6]−[4.5] colour to young stellar populations, this relation is more useful to infer the galaxy potential than the Mg b- vesc relation. [ABSTRACT FROM AUTHOR]

ABSTRACT We propose a simple model for the origin of fast and slow rotator early-type galaxies (ETG) within the hierarchical Λcold dark matter (ΛCDM) scenario, that is based on the assumption that the mass fraction of stellar discs in ETGs is a proxy for the specific angular momentum expressed via λ R. Within our model we reproduce the fraction of fast and slow rotators as a function of magnitude in the ATLAS3D survey, assuming that fast-rotating ETGs have at least 10 per cent of their total stellar mass in a disc component. In agreement with ATLAS3D observations we find that slow rotators are predominantly galaxies with M* > 1010.5 M⊙ contributing ∼20 per cent to the overall ETG population. We show in detail that the growth histories of fast and slow rotators are different, supporting the classification of ETGs into these two categories. Slow rotators accrete between ∼50 and 90 per cent of their stellar mass from satellites and their most massive progenitors have on average up to three major mergers during their evolution. Fast rotators in contrast accrete less than 50 per cent and have on average less than one major merger in their past. We find that the underlying physical reason for the different growth histories is the slowing down and ultimately complete shut-down of gas cooling in massive galaxies. Once cooling and associated star formation in disc stop, galaxies grow via infall from satellites. Frequent minor mergers thereby destroy existing stellar discs via violent relaxation and also tend to lower the specific angular momentum of the main stellar body, lowering λ R into the slow rotator regime. On average, the last gas-rich major merger interaction in slow rotators happens at z > 1.5, followed by a series of minor mergers. These results support the idea that kinematically decoupled cores (KDC) form during gas-rich major mergers at high z followed by minor mergers, which build-up the outer layers of the remnant, and make remnants that are initially too flat compared to observations become rounder. Fast rotators are less likely to form such KDCs due to the fact that they have on average less than one major merger in their past. Fast rotators in our model have different formation paths. The majority, 78 per cent, has bulge-to-total stellar mass ratios ( B/ T) > 0.5 and managed to grow stellar discs due to continued gas cooling or bulges due to frequent minor mergers. The remaining 22 per cent live in high-density environments and consist of low B/ T galaxies with gas fractions below 15 per cent, that have exhausted their cold gas reservoir and have no hot halo from which gas can cool. These fast rotators most likely resemble the flattened disc-like fast rotators in the ATLAS3D survey. Our results predict that ETGs can change their state from fast to slow rotator and vice versa, while the former is taking place predominantly at low z ( z < 2), the latter is occurring during cosmic epochs when cooling times are short and galaxies gas-rich. We predict that the ratio of the number density of slow to fast rotators is a strong function of redshift, with massive (>1010 M⊙) fast rotators being more than one order of magnitude more frequent at z∼ 2. [ABSTRACT FROM AUTHOR]

ABSTRACT The mass assembly of galaxies leaves imprints in their outskirts, such as shells and tidal tails. The frequency and properties of such fine structures depend on the main acting mechanisms - secular evolution, minor or major mergers - and on the age of the last substantial accretion event. We use this to constrain the mass assembly history of two apparently relaxed nearby early-type galaxies (ETGs) selected from the ATLAS3D sample, NGC 680 and 5557. Our ultra-deep optical images obtained with MegaCam on the Canada-France-Hawaii Telescope reach 29 mag arcsec−2 in the g band. They reveal very low surface brightness (LSB) filamentary structures around these ellipticals. Among them, a gigantic 160 kpc long, narrow, tail east of NGC 5557 hosts three gas-rich star-forming objects, previously detected in H i with the Westerbork Synthesis Radio Telescope and in UV with GALEX. NGC 680 exhibits two major diffuse plumes apparently connected to extended H i tails, as well as a series of arcs and shells. Comparing the outer stellar and gaseous morphology of the two ellipticals with that predicted from models of colliding galaxies, we argue that the LSB features are tidal debris and that each of these two ETGs was assembled during a relatively recent, major wet merger, which most likely occurred after the redshift z ≃ 0.5 epoch. Had these mergers been older, the tidal features should have already fallen back or be destroyed by more recent accretion events. However, the absence of molecular gas and of a prominent young stellar population in the core region of the galaxies indicates that the merger is at least 1-2 Gyr old: the memory of any merger-triggered nuclear starburst has indeed been lost. The star-forming objects found towards the collisional debris of NGC 5557 are then likely tidal dwarf galaxies. Such recycled galaxies here appear to be long-lived and continue to form stars while any star formation activity has stopped in their parent galaxy. The inner kinematics of NGC 680 is typical for fast rotators which make the bulk of nearby ETGs in the ATLAS3D sample. On the other hand, NGC 5557 belongs to the poorly populated class of massive, round, slow rotators that are predicted by semi-analytic models and cosmological simulations to be the end-product of a complex mass accretion history, involving ancient major mergers and more recent minor mergers. Our observations suggest that under specific circumstances a single binary merger may dominate the formation history of such objects and thus that at least some massive ETGs may form at relatively low redshift. Whether the two galaxies studied here are representative of their own sub-class of ETGs is still an open question that will be addressed by an on-going deep optical survey of ATLAS3D galaxies. [ABSTRACT FROM AUTHOR]

ABSTRACT We make use of interferometric CO and H i observations, and optical integral-field spectroscopy from the ATLAS3D survey, to probe the origin of the molecular and ionized interstellar medium (ISM) in local early-type galaxies. We find that 36 ± 5 per cent of our sample of fast-rotating early-type galaxies have their ionized gas kinematically misaligned with respect to the stars, setting a strong lower limit on the importance of externally acquired gas (e.g. from mergers and cold accretion). Slow rotators have a flat distribution of misalignments, indicating that the dominant source of gas is external. The molecular, ionized and atomic gas in all the detected galaxies are always kinematically aligned, even when they are misaligned from the stars, suggesting that all these three phases of the ISM share a common origin. In addition, we find that the origin of the cold and warm gas in fast-rotating early-type galaxies is strongly affected by environment, despite the molecular gas detection rate and mass fractions being fairly independent of group/cluster membership. Galaxies in dense groups and the Virgo cluster nearly always have their molecular gas kinematically aligned with the stellar kinematics, consistent with a purely internal origin (presumably stellar mass loss). In the field, however, kinematic misalignments between the stellar and gaseous components indicate that at least 42 ± 5 per cent of local fast-rotating early-type galaxies have their gas supplied from external sources. When one also considers evidence of accretion present in the galaxies' atomic gas distributions, ≳46 per cent of fast-rotating field ETGs are likely to have acquired a detectable amount of ISM from accretion and mergers. We discuss several scenarios which could explain the environmental dichotomy, including preprocessing in galaxy groups/cluster outskirts and the morphological transformation of spiral galaxies, but we find it difficult to simultaneously explain the kinematic misalignment difference and the constant detection rate. Furthermore, our results suggest that galaxy mass may be an important independent factor associated with the origin of the gas, with the most massive fast-rotating galaxies in our sample (M K≲−24 mag; stellar mass of ≈8 × 1010 M⊙) always having kinematically aligned gas. This mass dependence appears to be independent of environment, suggesting it is caused by a separate physical mechanism. [ABSTRACT FROM AUTHOR]

ABSTRACT We study the formation of early-type galaxies (ETGs) through mergers with a sample of 70 high-resolution (softening length <60 pc and 12 × 106 particles) numerical simulations of binary mergers of disc galaxies (with 10 per cent of gas) and 16 simulations of ETG remergers. These simulations, designed to accompany observations and models conducted within the ATLAS3D project, encompass various mass ratios (from 1:1 to 6:1), initial conditions and orbital parameters. The progenitor disc galaxies are spiral-like with bulge-to-disc ratios typical of Sb and Sc galaxies and high central baryonic angular momentum. We find that binary mergers of disc galaxies with mass ratios of 3:1 and 6:1 are nearly always classified as fast rotators according to the ATLAS3D criterion (based on the λR parameter - ATLAS3D Paper III): they preserve the structure of the input fast rotating spiral progenitors. They have intrinsic ellipticities larger than 0.5, cover intrinsic λR values between 0.2 and 0.6, within the range of observed fast rotators. The distribution of the observed fastest rotators does in fact coincide with the distribution of our disc progenitors. Major disc mergers (mass ratios of 2:1 and 1:1) lead to both fast and slow rotators. Most of the fast rotators produced in major mergers have intermediate flattening, with ellipticities ε between 0.4 and 0.6. Most slow rotators formed in these binary disc mergers hold a stellar kinematically distinct core (KDC) in their ∼1-3 central kiloparsec: these KDCs are built from the stellar components of the progenitors. However, these remnants are still very flat with ε often larger than 0.45 and sometimes as high as 0.65. Besides a handful of specific observed systems - the counter-rotating discs (2σ galaxies, ATLAS3D Paper II) - these therefore cannot reproduce the observed population of slow rotators in the nearby Universe. This sample of simulations supports the notion of slow and fast rotators: these two families of ETGs present distinct characteristics in term of their angular momentum content (at all radii) and intrinsic properties - the slow rotators are not simply velocity-scaled down versions of fast rotators. The mass ratio of the progenitors is a fundamental parameter for the formation of slow rotators in these binary mergers, but it also requires a retrograde spin for the earlier-type (Sb) progenitor galaxy with respect to the orbital angular momentum. We also study remergers of these merger remnants: these produce relatively round fast rotators or systems near the threshold for slow rotators. In such cases, the orbital angular momentum dominates the central region, and these systems no longer exhibit a KDC, as KDCs are destroyed during the remergers and do not re-form in these relatively dry events. [ABSTRACT FROM AUTHOR]

ABSTRACT In Paper I of this series we introduced a volume-limited parent sample of 871 galaxies from which we extracted the ATLAS3D sample of 260 early-type galaxies (ETGs). In Papers II and III we classified the ETGs using their stellar kinematics, in a way that is nearly insensitive to the projection effects, and we separated them into fast and slow rotators. Here we look at galaxy morphology and note that the edge-on fast rotators generally are lenticular galaxies. They appear like spiral galaxies with the gas and dust removed, and in some cases are flat ellipticals (E5 or flatter) with discy isophotes. Fast rotators are often barred and span the same full range of bulge fractions as spiral galaxies. The slow rotators are rounder (E4 or rounder, except for counter-rotating discs) and are generally consistent with being genuine, namely spheroidal-like, elliptical galaxies. We propose a revision to the tuning-fork diagram by Hubble as it gives a misleading description of ETGs by ignoring the large variation in the bulge sizes of fast rotators. Motivated by the fact that only one third (34 per cent) of the ellipticals in our sample are slow rotators, we study for the first time the kinematic morphology-density T-Σ relation using fast and slow rotators to replace lenticulars and ellipticals. We find that our relation is cleaner than using classic morphology. Slow rotators are nearly absent at the lowest density environments [ per cent] and generally constitute a small fraction [ f(SR) ≈ 4 per cent] of the total galaxy population in the relatively low-density environments explored by our survey, with the exception of the densest core of the Virgo cluster [ f(SR) ≈ 20 per cent]. This contrasts with the classic studies that invariably find significant fractions of (misclassified) ellipticals down to the lowest environmental densities. We find a clean log-linear relation between the fraction f(Sp) of spiral galaxies and the local galaxy surface density Σ3, within a cylinder enclosing the three nearest galaxies. This holds for nearly four orders of magnitude in the surface density down to Σ3≈ 0.01 Mpc−2, with f(Sp) decreasing by 10 per cent per dex in Σ3, while f(FR) correspondingly increases. The existence of a smooth kinematic T-Σ relation in the field excludes processes related to the cluster environment, like e.g. ram-pressure stripping, as main contributors to the apparent conversion of spirals into fast rotators in low-density environments. It shows that the segregation is driven by local effects at the small-group scale. This is supported by the relation becoming shallower when using a surface density estimator Σ10 with a cluster scale. Only at the largest densities in the Virgo core does the f(Sp) relation break down and steepen sharply, while the fraction of slow rotators starts to significantly increase. This suggests that a different mechanism is at work there, possibly related to the stripping of the gas from spirals by the hot intergalactic medium in the cluster core and the corresponding lack of cold accretion. [ABSTRACT FROM AUTHOR]

BSTRACT [ABSTRACT FROM AUTHOR]

Using far-ultraviolet (FUV) and near-ultraviolet (NUV) photometry from guest investigator programmes on the Galaxy Evolution Explorer ( GALEX) satellite, optical photometry from the MDM Observatory and optical integral-field spectroscopy from SAURON, we explore the UV-line-strength relations of the 48 nearby early-type galaxies in the SAURON sample. Identical apertures are used for all quantities, avoiding aperture mismatch. We show that galaxies with purely old stellar populations show well-defined correlations of the integrated and colours with the integrated Mg and Hβ absorption line-strength indices, strongest for . Correlations with the colour, Fe5015 index and stellar velocity dispersion σ are much weaker. These correlations put stringent constraints on the origin of the UV-upturn phenomenon in early-type galaxies and highlight its dependence on age and metallicity. In particular, despite recent debate, we recover the negative correlation between colour and Mg line strength originally publicized by , which we refer to as the 'Burstein relation', suggesting a positive dependence of the UV upturn on metallicity. We argue that the scatter in the correlations is real and present mild evidence that a strong UV excess is preferentially present in slow-rotating galaxies. We also demonstrate that most outliers in the correlations are galaxies with current or recent star formation, some at very low levels. We believe that this sensitivity to weak star formation, afforded by the deep and varied data available for the SAURON sample, explains why our results are occasionally at odds with other recent but shallower surveys. This is supported by the analysis of a large, carefully crafted sample of more distant early-type galaxies from the Sloan Digital Sky Survey (SDSS), more easily comparable with current and future large surveys. [ABSTRACT FROM AUTHOR]

We provide a census of the apparent stellar angular momentum within one effective radius of a volume-limited sample of 260 early-type galaxies (ETGs) in the nearby Universe, using the integral-field spectroscopy obtained in the course of the ATLAS project. We exploit the λ parameter (previously used via a constant threshold value of 0.1) to characterize the existence of two families of ETGs: slow rotators which exhibit complex stellar velocity fields and often include stellar kinematically distinct cores, and fast rotators which have regular velocity fields. Our complete sample of 260 ETGs leads to a new criterion to disentangle fast and slow rotators which now includes a dependency on the apparent ellipticity ε. It separates the two classes significantly better than the previous prescription and better than a criterion based on V/σ: slow rotators and fast rotators have λ lower and larger than , respectively, where k= 0.31 for measurements made within an effective radius R. We show that the vast majority of ETGs are fast rotators: these have the regular stellar rotation, with aligned photometric and kinematic axes (Paper II of this series), include discs and often bars and represent 86 ± 2 per cent (224/260) of all ETGs in the volume-limited ATLAS sample. Fast rotators span the full range of apparent ellipticities from ε= 0 to 0.85, and we suggest that they cover intrinsic ellipticities from about 0.35 to 0.85, the most flattened having morphologies consistent with spiral galaxies. Only a small fraction of ETGs are slow rotators representing 14 ± 2 per cent (36/260) of the ATLAS sample of ETGs. Of all slow rotators, 11 per cent (4/36) exhibit two counter-rotating stellar disc-like components and are rather low-mass objects ( M < 10 M). All other slow rotators (32/36) appear relatively round on the sky (ε < 0.4), tend to be massive ( M > 10 M), and often (17/32) exhibit kinematically distinct cores. Slow rotators dominate the high-mass end of ETGs in the ATLAS sample, with only about one-fourth of galaxies with masses above 10 M being fast rotators. We show that the a parameter which quantifies the isophote's disciness or boxiness does not seem to be simply related to the observed kinematics, while our new criterion based on λ and ε is nearly independent of the viewing angles. We further demonstrate that the classification of ETGs into ellipticals and lenticulars is misleading. Slow and fast rotators tend to be classified as ellipticals and lenticulars, respectively, but the contamination is strong enough to affect results solely based on such a scheme: 20 per cent of all fast rotators are classified as ellipticals, and more importantly 66 per cent of all ellipticals in the ATLAS sample are fast rotators. Fast and slow rotators illustrate the variety of complex processes shaping galactic systems, such as secular evolution, disc instabilities, interaction and merging, gas accretion, stripping and harassment, forming a sequence from high to low (stellar) baryonic angular momentum. Massive slow rotators represent the extreme instances within the red sequence of galaxies which might have suffered from significant merging without being able to rebuild a fast-rotating component within one effective radius. We therefore argue for a shift in the paradigm for ETGs, where the vast majority of ETGs are galaxies consistent with nearly oblate systems (with or without bars) and where only a small fraction of them (less than 12 per cent) have central (mildly) triaxial structures. [ABSTRACT FROM AUTHOR]

We have carried out a survey for CO J= 1-0 and J= 2-1 emission in the 260 early-type galaxies of the volume-limited ATLAS sample, with the goal of connecting their star formation and assembly histories to their cold gas content. This is the largest volume-limited CO survey of its kind and is the first to include many Virgo cluster members. Sample members are dynamically hot galaxies with a median stellar mass ∼3 × 10 M; they are selected by their morphology rather than colour, and the bulk of them lie on the red sequence. The overall CO detection rate is 56/259 = 0.22 ± 0.03, with no dependence on the K luminosity and only a modest dependence on the dynamical mass. There are a dozen CO detections among the Virgo cluster members; statistical analysis of their H mass distributions and their dynamical status within the cluster shows that the cluster's influence on their molecular masses is subtle at best, even though (unlike spirals) they seem to be virialized within the cluster. We suggest that the cluster members have retained their molecular gas through several Gyr residences in the cluster. There are also a few extremely CO-rich early-type galaxies with H masses ≳10 M and these are in low-density environments. We do find a significant trend between the molecular content and stellar specific angular momentum. The galaxies of low angular momentum also have low CO detection rates, suggesting that their formation processes were more effective at destroying the molecular gas or preventing its re-accretion. We speculate on the implications of these data for the formation of various subclasses of early-type galaxies. [ABSTRACT FROM AUTHOR]

We demonstrate here using both single-dish and interferometric observations that CO molecules are an excellent kinematic tracer, even in high-mass galaxies, allowing us to investigate for the first time the CO Tully-Fisher relation (CO-TFR) of early-type galaxies. We compare the TFRs produced using both single-dish and interferometric data and various inclination estimation methods, and evaluate the use of the velocity profile shape as a criterion for selecting galaxies in which the molecular gas extends beyond the peak of the rotation curve. We show that the gradient and zero-point of the best-fitting relations are robust, independent of the velocity measure and inclination used, and agree with those of relations derived using stellar kinematics. We also show that the early-type CO-TFR is offset from the CO-TFR of spirals by 0.98 ± 0.22 mag at K band, in line with other results. The intrinsic scatter of the relation is found to be ≈0.4 mag, similar to the level found in the spiral galaxy population. Next-generation facilities such as the Large Millimeter Telescope and the Atacama Large Millimeter/Sub-millimeter Array should allow this technique to be used in higher redshift systems, providing a simple new tool to trace the mass-to-light ratio evolution of the most massive galaxies over cosmic time. [ABSTRACT FROM AUTHOR]

The ATLAS project is a multiwavelength survey combined with a theoretical modelling effort. The observations span from the radio to the millimetre and optical, and provide multicolour imaging, two-dimensional kinematics of the atomic (H ), molecular (CO) and ionized gas (H, [O ] and [N ]), together with the kinematics and population of the stars (H, Fe5015 and Mg b), for a carefully selected, volume-limited ( Mpc) sample of 260 early-type (elliptical E and lenticular S0) galaxies (ETGs). The models include semi-analytic, N-body binary mergers and cosmological simulations of galaxy formation. Here we present the science goals for the project and introduce the galaxy sample and the selection criteria. The sample consists of nearby ( Mpc, |δ− 29°| < 35°, | b| > 15°) morphologically selected ETGs extracted from a parent sample of 871 galaxies (8 per cent E, 22 per cent S0 and 70 per cent spirals) brighter than mag (stellar mass ). We analyse possible selection biases and we conclude that the parent sample is essentially complete and statistically representative of the nearby galaxy population. We present the size-luminosity relation for the spirals and ETGs and show that the ETGs in the ATLAS sample define a tight red sequence in a colour-magnitude diagram, with few objects in the transition from the blue cloud. We describe the strategy of the SAURON integral field observations and the extraction of the stellar kinematics with the p method. We find typical 1 errors of km s km s in the mean velocity, the velocity dispersion and Gauss-Hermite (GH) moments for galaxies with effective dispersion km s. For galaxies with lower (40 per cent of the sample) the GH moments are gradually penalized by p towards zero to suppress the noise produced by the spectral undersampling and only and can be measured. We give an overview of the characteristics of the other main data sets already available for our sample and of the ongoing modelling projects. [ABSTRACT FROM AUTHOR]

ABSTRACT We present a stellar population analysis of the absorption line strength maps for 48 early-type galaxies from the SAURON sample. Using the line strength index maps of Hβ, Fe5015 and Mg b, measured in the Lick/IDS system and spatially binned to a constant signal-to-noise ratio, together with predictions from up-to-date stellar population models, we estimate the simple stellar population-equivalent (SSP-equivalent) age, metallicity and abundance ratio [α/Fe] over a two-dimensional field extending up to approximately one effective radius. A discussion of calibrations and differences between model predictions is given. Maps of SSP-equivalent age, metallicity and abundance ratio [α/Fe] are presented for each galaxy. We find a large range of SSP-equivalent ages in our sample, of which ∼40 per cent of the galaxies show signs of a contribution from a young stellar population. The most extreme cases of post-starburst galaxies, with SSP-equivalent ages of ≤3 Gyr observed over the full field-of-view, and sometimes even showing signs of residual star formation, are restricted to low-mass systems ( σe≤ 100 km s−1 or ∼ 2 × 1010 M⊙). Spatially restricted cases of young stellar populations in circumnuclear regions can almost exclusively be linked to the presence of star formation in a thin, dusty disc/ring, also seen in the near-UV or mid-IR on top of an older underlying stellar population. The flattened components with disc-like kinematics previously identified in all fast rotators are shown to be connected to regions of distinct stellar populations. These range from the young, still star-forming circumnuclear discs and rings with increased metallicity preferentially found in intermediate-mass fast rotators, to apparently old structures with extended disc-like kinematics, which are observed to have an increased metallicity and mildly depressed [α/Fe] ratio compared to the main body of the galaxy. The slow rotators, often harbouring kinematically decoupled components (KDC) in their central regions, generally show no stellar population signatures over and above the well-known metallicity gradients in early-type galaxies and are largely consistent with old (≥10 Gyr) stellar populations. Using radially averaged stellar population gradients we find in agreement with Spolaor et al. a mass-metallicity gradient relation where low-mass fast rotators form a sequence of increasing metallicity gradient with increasing mass. For more massive systems (above ∼3.5 × 1010 M⊙) there is an overall downturn such that metallicity gradients become shallower with increased scatter at a given mass leading to the most massive systems being slow rotators with relatively shallow metallicity gradients. The observed shallower metallicity gradients and increased scatter could be a consequence of the competition between different star formation and assembly scenarios following a general trend of diminishing gas fractions and more equal-mass mergers with increasing mass, leading to the most massive systems being devoid of ordered motion and signs of recent star formation. [ABSTRACT FROM AUTHOR]

Following our study on the incidence, morphology and kinematics of the ionized gas in early-type galaxies, we now address the question of what is powering the observed nebular emission. To constrain the likely sources of gas excitation, we resort to a variety of ancillary data we draw from complementary information on the gas kinematics, stellar populations and galactic potential from thesauron data, and use thesauron-specific diagnostic diagram juxtaposing the [O iii] /Hβ and [N i] /Hβ line ratios. We find a tight correlation between the stellar surface brightness and the flux of the Hβ recombination line across our sample, which points to a diffuse and old stellar source as the main contributor of ionizing photons in early-type galaxies, with post-asymptotic giant branch (pAGB) stars being still the best candidate based on ionizing balance arguments. The role of AGN photoionization is confined to the central 2–3 arcsec of an handful of objects with radio or X-ray cores. OB-stars are the dominant source of photoionization in 10 per cent of thesauron sample, whereas for another 10 per cent the intense and highly ionized emission is powered by the pAGB population associated to a recently formed stellar subcomponent. Fast shocks are not an important source of ionization for the diffuse nebular emission of early-type galaxies since the required shock velocities can hardly be attained in the potential of our sample galaxies. Finally, in the most massive and slowly or non-rotating galaxies in our sample, which can retain a massive X-ray halo, the finding of a spatial correlation between the hot and warm phases of the interstellar medium (ISM) suggests that the interaction with the hot ISM provides an additional source of ionization besides old ultraviolet-bright stars. This is also supported by a distinct pattern towards lower values of the [O iii]/Hβ ratio. These results lead us to investigate the relative role of stellar and AGN photoionization in explaining the ionized gas emission observed in early-type galaxies by the Sloan Digital Sky Survey (SDSS). By simulating how our sample galaxies would appear if placed at further distance and targeted by the SDSS, we conclude that only in very few, if any, of the SDSS galaxies which display modest values for the equivalent width of the [O iii] line (less than ∼2.4 Å) and low-ionization nuclear emission-line region like [O iii]/Hβ values the nebular emission is truly powered by an AGN. [ABSTRACT FROM AUTHOR]

We combine SAURON integral field data of a representative sample of local early-type, red sequence galaxies with Spitzer/Infrared Array Camera imaging in order to investigate the presence of trace star formation in these systems. With the Spitzer data, we identify galaxies hosting low-level star formation, as traced by polycyclic aromatic hydrocarbon emission, with measured star formation rates that compare well to those estimated from other tracers. This star formation proceeds according to established scaling relations with molecular gas content, in surface density regimes characteristic of disc galaxies and circumnuclear starbursts. We find that star formation in early-type galaxies happens exclusively in fast-rotating systems and occurs in two distinct modes. In the first, star formation is a diffuse process, corresponding to widespread young stellar populations and high molecular gas content. The equal presence of co- and counter-rotating components in these systems strongly implies an external origin for the star-forming gas, and we argue that these star formation events may be the final stages of (mostly minor) mergers that build up the bulges of red sequence lenticulars. In the second mode of star formation, the process is concentrated into well-defined disc or ring morphologies, outside of which the host galaxies exhibit uniformly evolved stellar populations. This implies that these star formation events represent rejuvenations within previously quiescent stellar systems. Evidence for earlier star formation events similar to these in all fast-rotating early-type galaxies suggests that this mode of star formation may be common to all such galaxies, with a duty cycle of roughly 1/10, and likely contributes to the embedded, corotating inner stellar discs ubiquitous in this population. [ABSTRACT FROM AUTHOR]

We present observations of early-type galaxies NGC 524 and 2549 with laser guide star adaptive optics (LGS AO) obtained at GEMINI North telescope using the Near-infrared Integral Field Spectrograph (NIFS) integral field unit (IFU) in the K band. The purpose of these observations is to determine high spatial resolution stellar kinematics within the nuclei of these galaxies and, in combination with previously obtained large-scale observations with the SAURON IFU, to determine the masses of the supermassive black holes (SMBH). The targeted galaxies were chosen to have central light profiles showing a core (NGC 524) and a cusp (NGC 2549), to probe the feasibility of using the galaxy centre as the natural guide source required for LGS AO. We employ an innovative technique where the focus compensation due to the changing distance to the sodium layer is made ‘open loop’, allowing the extended galaxy nucleus to be used only for tip-tilt correction. The data have spatial resolution of 0.23 and 0.17 arcsec full-width at half maximum (FWHM), where at least ∼40 per cent of flux comes within 0.2, showing that high quality LGS AO observations of these objects are possible. The achieved signal-to-noise ratio (S/N ∼ 50) is sufficiently high to reliably determine the shape of the line-of-sight velocity distribution. We construct axisymmetric three-integral dynamical models which are constrained with both the NIFS and SAURON data. The best-fitting models yield and for NGC 524 and and for NGC 2549 (all errors are at the level). We demonstrate that the wide-field SAURON data play a crucial role in the M/L determination increasing the accuracy of M/L by a factor of at least 5, and constraining the upper limits on black hole masses. The NIFS data are crucial in constraining the lower limits of and in combination with the large-scale data reducing the uncertainty by a factor of 2 or more. We find that the orbital structure of NGC 524 shows significant tangential anisotropy, while at larger radii both galaxies are consistent with having almost perfectly oblate velocity ellipsoids. Tangential anisotropy in NGC 524 coincides with the size of SMBH sphere of influence and the core region in the light profile. This agrees with predictions from numerical simulations where core profiles are the result of SMBH binaries evacuating the centre nuclear regions following a galaxy merger. However, being a disc dominated fast rotating galaxy, NGC 524 has probably undergone through a more complex evolution. We test the accuracy to which can be measured using seeings obtained from typical LGS AO observations, and conclude that for a typical conditions and the expected uncertainty is of the order of 50 per cent. [ABSTRACT FROM AUTHOR]

We present Galaxy Evolution Explorer far-ultraviolet (FUV) and near-ultraviolet (NUV) imaging of 34 nearby early-type galaxies from the SAURON representative sample of 48 E/S0 galaxies, all of which have ground-based optical imaging from the MDM Observatory. The surface brightness profiles of nine galaxies (≈26 per cent) show regions with blue UV−optical colours suggesting RSF. Five of these (≈15 per cent) show blue integrated UV–optical colours that set them aside in the NUV integrated colour–magnitude relation. These are objects with either exceptionally intense and localized NUV fluxes or blue UV−optical colours throughout. They also have other properties confirming they have had RSF, in particular Hβ absorption higher than expected for a quiescent population and a higher CO detection rate. This suggests that residual star formation is more common in early-type galaxies than we are used to believe. NUV blue galaxies are generally drawn from the lower stellar velocity dispersion and thus lower dynamical mass part of the sample. We have also constructed the first UV Fundamental Planes and show that NUV blue galaxies bias the slopes and increase the scatters. If they are eliminated, the fits get closer to expectations from the virial theorem. Although our analysis is based on a limited sample, it seems that a dominant fraction of the tilt and scatter of the UV Fundamental Planes is due to the presence of young stars in preferentially low-mass early-type galaxies. Interestingly, the UV–optical radial colour profiles reveal a variety of behaviours, with many galaxies showing signs of RSF, a central UV-upturn phenomenon, smooth but large-scale age and metallicity gradients and in many cases a combination of these. In addition, FUV−NUV and FUV− V colours even bluer than those normally associated with UV-upturn galaxies are observed at the centre of some quiescent galaxies. Four out of the five UV-upturn galaxies are slow rotators. These objects should thus pose interesting challenges to stellar evolutionary models of the UV upturn. [ABSTRACT FROM AUTHOR]