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  • 1
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    The ATLAS3D project - XVII. Linking photometric and kinematic signatures of stellar discs in early-type galaxies (2013)
    Oxford University Press
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    Publication Date: 2013-06-09
    Description: We analyse the morphological structures in galaxies of the ATLAS 3D sample by fitting a single Sérsic profile and decomposing all non-barred objects (180 of 260 objects) in two components parametrized by an exponential and a general Sérsic function. The aim of this analysis is to look for signatures of discs in light distributions of nearby early-type galaxies and compare them to kinematic properties. Using Sérsic index from single-component fits for a distinction between slow and fast rotators, or even late- and early-type galaxies, is not recommended. Assuming that objects with n  〉 3 are slow rotators (or ellipticals), there is only a 22 per cent probability to correctly classify objects as slow rotators (or 37 per cent of previously classified as ellipticals). We show that exponential sub-components, as well as light profiles fitted with only a single component of a low Sérsic index, can be linked with the kinematic evidence for discs in early-type galaxies. The median disc-to-total light ratio for fast and slow rotators is 0.41 and 0.0, respectively. Similarly, the median Sérsic indices of the bulge (general Sérsic component) are 1.7 and 4.8 for fast and slow rotators, respectively. Overall, discs or disc-like structures are present in 83 per cent of early-type galaxies which do not have bars, and they show a full range of disc-to-total light ratios. Discs in early-type galaxies contribute with about 40 per cent to the total mass of the analysed (non-barred) objects. The decomposition into discs and bulges can be used as a rough approximation for the separation between fast and slow rotators, but it is not a substitute, as there is only a 59 per cent probability to correctly recognize slow rotators. We find trends between the angular momentum and the disc-to-total light ratios and the Sérsic index of the bulge, in the sense that high angular momentum galaxies have large disc-to-total light ratios and small bulge indices, but there is none between the angular momentum and the global Sérsic index. We investigate the inclination effects on the decomposition results and confirm that strong exponential profiles can be distinguished even at low inclinations, but medium-size discs are difficult to quantify using photometry alone at inclinations lower than ~50°. Kinematics (i.e. projected angular momentum) remains the best approach to mitigate the influence of the inclination effects. We also find weak trends with mass and environmental density, where disc-dominated galaxies are typically less massive and found at all densities, including the densest region sampled by the ATLAS 3D sample.
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    Electronic ISSN: 1365-2966
    Topics: Physics
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  • 2
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    The ATLAS3D project - XVIII. CARMA CO imaging survey of early-type galaxies (2013)
    Oxford University Press
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    Publication Date: 2013-06-09
    Description: We present the Combined Array for Research in Millimeter Astronomy (CARMA) ATLAS 3D molecular gas imaging survey, a systematic study of the distribution and kinematics of molecular gas in CO-rich early-type galaxies. Our full sample of 40 galaxies (30 newly mapped and 10 taken from the literature) is complete to a 12 CO(1–0) integrated flux of 18.5 Jy km s –1 , 1 and it represents the largest, best studied sample of its type to date. A comparison of the CO distribution of each galaxy to the g  – r colour image (representing dust) shows that the molecular gas and dust distributions are in good agreement and trace the same underlying interstellar medium. The galaxies exhibit a variety of CO morphologies, including discs (50 per cent), rings (15 per cent), bars+rings (10 per cent), spiral arms (5 per cent) and mildly (12.5 per cent) and strongly (7.5 per cent) disrupted morphologies. There appear to be weak trends between galaxy mass and CO morphology, whereby the most massive galaxies in the sample tend to have molecular gas in a disc morphology. We derive a lower limit to the total accreted molecular gas mass across the sample of 2.48  x 10 10 M , or approximately 8.3  x 10 8 M per minor merger within the sample, consistent with minor merger stellar mass ratios.
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    Electronic ISSN: 1365-2966
    Topics: Physics
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  • 3
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    The ATLAS3D Project - XXX. Star formation histories and stellar population scaling relations of early-type galaxies (2015)
    Oxford University Press
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    Publication Date: 2015-03-13
    Description: We present the stellar population content of early-type galaxies from the ATLAS 3D 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 ( M JAM , e , $R^{\rm maj}_{\rm e}$ ), 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 (〉10 10.5  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.
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    Topics: Physics
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  • 4
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    The ATLAS3D project - XXIX. The new look of early-type galaxies and surrounding fields disclosed by extremely deep optical images (2014)
    Oxford University Press
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    Publication Date: 2014-11-12
    Description: 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 ATLAS 3D 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 ATLAS 3D 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.
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    Electronic ISSN: 1365-2966
    Topics: Physics
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  • 5
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    Isolation of a cDNA from the virus responsible for enterically transmitted non-A, non-B hepatitis (1990)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1990-03-16
    Description: Major epidemic outbreaks of viral hepatitis in underdeveloped countries result from a type of non-A, non-B hepatitis distinct from the parenterally transmitted form. The viral agent responsible for this form of epidemic, or enterically transmitted non-A, non-B hepatitis (ET-NANBH), has been serially transmitted in cynomolgus macaques (cynos) and has resulted in typical elevation in liver enzymes and the detection of characteristic virus-like particles (VLPs) in both feces and bile. Infectious bile was used for the construction of recombinant complementary DNA libraries. One clone, ET1.1, was exogenous to uninfected human and cyno genomic liver DNA, as well as to genomic DNA from infected cyno liver. ET1.1 did however, hybridize to an approximately 7.6-kilobase RNA species present only in infected cyno liver. The translated nucleic acid sequence of a portion of ET1.1 had a consensus amino acid motif consistent with an RNA-directed RNA polymerase; this enzyme is present in all positive strand RNA viruses. Furthermore, ET1.1 specifically identified similar sequences in complementary DNA prepared from infected human fecal samples collected from five geographically distinct ET-NANBH outbreaks. Therefore, ET1.1 represents a portion of the genome of the principal viral agent, to be named hepatitis E virus, which is responsible for epidemic outbreaks of ET-NANBH.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Reyes, G R -- Purdy, M A -- Kim, J P -- Luk, K C -- Young, L M -- Fry, K E -- Bradley, D W -- New York, N.Y. -- Science. 1990 Mar 16;247(4948):1335-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Molecular Virology Department, Genelabs Incorporated, Redwood City, CA 94063.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2107574" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; Base Sequence ; Cloning, Molecular ; DNA/genetics ; Hepatitis E/*microbiology ; Hepatitis Viruses/*genetics ; Hepatitis, Viral, Human/*microbiology ; Humans ; Macaca fascicularis ; Molecular Sequence Data ; Polymerase Chain Reaction ; RNA Viruses/genetics ; RNA, Viral/genetics ; Restriction Mapping
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 6
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    Systematic variation of the stellar initial mass function in early-type galaxies (2012)
    Nature Publishing Group (NPG)
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    Publication Date: 2012-04-28
    Description: Much of our knowledge of galaxies comes from analysing the radiation emitted by their stars, which depends on the present number of each type of star in the galaxy. The present number depends on the stellar initial mass function (IMF), which describes the distribution of stellar masses when the population formed, and knowledge of it is critical to almost every aspect of galaxy evolution. More than 50 years after the first IMF determination, no consensus has emerged on whether it is universal among different types of galaxies. Previous studies indicated that the IMF and the dark matter fraction in galaxy centres cannot both be universal, but they could not convincingly discriminate between the two possibilities. Only recently were indications found that massive elliptical galaxies may not have the same IMF as the Milky Way. Here we report a study of the two-dimensional stellar kinematics for the large representative ATLAS(3D) sample of nearby early-type galaxies spanning two orders of magnitude in stellar mass, using detailed dynamical models. We find a strong systematic variation in IMF in early-type galaxies as a function of their stellar mass-to-light ratios, producing differences of a factor of up to three in galactic stellar mass. This implies that a galaxy's IMF depends intimately on the galaxy's formation history.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cappellari, Michele -- McDermid, Richard M -- Alatalo, Katherine -- Blitz, Leo -- Bois, Maxime -- Bournaud, Frederic -- Bureau, M -- Crocker, Alison F -- Davies, Roger L -- Davis, Timothy A -- de Zeeuw, P T -- Duc, Pierre-Alain -- Emsellem, Eric -- Khochfar, Sadegh -- Krajnovic, Davor -- Kuntschner, Harald -- Lablanche, Pierre-Yves -- Morganti, Raffaella -- Naab, Thorsten -- Oosterloo, Tom -- Sarzi, Marc -- Scott, Nicholas -- Serra, Paolo -- Weijmans, Anne-Marie -- Young, Lisa M -- England -- Nature. 2012 Apr 25;484(7395):485-8. doi: 10.1038/nature10972.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics, University of Oxford, Oxford OX1 3RH, UK. cappellari@astro.ox.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22538610" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 7
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    The ATLAS3D project - XV. Benchmark for early-type galaxies scaling relations from 260 dynamical models: mass-to-light ratio, dark matter, Fundamental Plane and Mass Plane (2013)
    Oxford University Press
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    Publication Date: 2013-06-09
    Description: We study the volume-limited and nearly mass-selected (stellar mass M stars 6 x 10 9 M ) ATLAS 3D sample of 260 early-type galaxies (ETGs, ellipticals Es and lenticulars S0s). We construct detailed axisymmetric dynamical models (Jeans Anisotropic MGE), which allow for orbital anisotropy, include a dark matter halo and reproduce in detail both the galaxy images and the high-quality integral-field stellar kinematics out to about 1 R e , the projected half-light radius. We derive accurate total mass-to-light ratios (M/L) e and dark matter fractions f DM , within a sphere of radius $r={R_{\rm e}}$ centred on the galaxies. We also measure the stellar (M/L) stars and derive a median dark matter fraction f DM  = 13 per cent in our sample. We infer masses M JAM L x (M/L) e 2 x M 1/2 , where M 1/2 is the total mass within a sphere enclosing half of the galaxy light. We find that the thin two-dimensional subset spanned by galaxies in the $(M_{\rm JAM},\sigma _e,R_{\rm e}^{\rm maj})$ coordinates system, which we call the Mass Plane (MP) has an observed rms scatter of 19 per cent, which implies an intrinsic one of 11 per cent. Here, $R_{\rm e}^{\rm maj}$ is the major axis of an isophote enclosing half of the observed galaxy light, while e is measured within that isophote. The MP satisfies the scalar virial relation $M_{\rm JAM}\propto \sigma _e^2 R_{\rm e}^{\rm maj}$ within our tight errors. This show that the larger scatter in the Fundamental Plane (FP) ( L , e , R e ) is due to stellar population effects [including trends in the stellar initial mass function (IMF)]. It confirms that the FP deviation from the virial exponents is due to a genuine (M/L) e variation. However, the details of how both R e and e are determined are critical in defining the precise deviation from the virial exponents. The main uncertainty in masses or M/L estimates using the scalar virial relation is in the measurement of R e . This problem is already relevant for nearby galaxies and may cause significant biases in virial mass and size determinations at high redshift. Dynamical models can eliminate these problems. We revisit the (M/L) e - e relation, which describes most of the deviations between the MP and the FP. The best-fitting relation is $({\rm M/L})_e\propto \sigma _e^{0.72}$ ( r band). It provides an upper limit to any systematic increase of the IMF mass normalization with e . The correlation is more shallow and has smaller scatter for slow rotating systems or for galaxies in Virgo. For the latter, when using the best distance estimates, we observe a scatter in (M/L) e of 11 per cent, and infer an intrinsic one of 8 per cent. We perform an accurate empirical study of the link between e and the galaxies circular velocity V circ within 1 R e (where stars dominate) and find the relation max ( V circ )  1.76  x e , which has an observed scatter of 7 per cent. The accurate parameters described in this paper are used in the companion Paper XX (Cappellari et al.) of this series to explore the variation of global galaxy properties, including the IMF, on the projections of the MP.
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    Topics: Physics
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  • 8
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    The ATLAS3D project - XXII. Low-efficiency star formation in early-type galaxies: hydrodynamic models and observations (2013)
    Oxford University Press
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    Publication Date: 2013-06-09
    Description: We study the global efficiency of star formation in high-resolution hydrodynamical simulations of gas discs embedded in isolated early-type and spiral galaxies. Despite using a universal local law to form stars in the simulations, we find that the early-type galaxies are offset from the spirals on the large-scale Kennicutt relation, and form stars two to five times less efficiently. This offset is in agreement with previous results on morphological quenching: gas discs are more stable against star formation when embedded in early-type galaxies due to the lower disc self-gravity and increased shear. As a result, these gas discs do not fragment into dense clumps and do not reach as high densities as in the spiral galaxies. Even if some molecular gas is present, the fraction of very dense gas (typically above 10 4 cm –3 ) is significantly reduced, which explains the overall lower star formation efficiency. We also analyse a sample of local early-type and spiral galaxies, measuring their CO and H i surface densities and their star formation rates as determined by their non-stellar 8 μm emission. As predicted by the simulations, we find that the early-type galaxies are offset from the Kennicutt relation compared to the spirals, with a twice lower efficiency. Finally, we validate our approach by performing a direct comparison between models and observations. We run a simulation designed to mimic the stellar and gaseous properties of NGC 524, a local lenticular galaxy, and find a gas disc structure and global star formation rate in good agreement with the observations. Morphological quenching thus seems to be a robust mechanism, and is also consistent with other observations of a reduced star formation efficiency in early-type galaxies in the COLD GASS survey. This lower efficiency of star formation is not enough to explain the formation of the whole red sequence, but can contribute to the reddening of some galaxies.
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    Topics: Physics
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  • 9
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    The ATLAS3D project - XX. Mass-size and mass-{sigma} distributions of early-type galaxies: bulge fraction drives kinematics, mass-to-light ratio, molecular gas fraction and stellar initial mass function (2013)
    Oxford University Press
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    Publication Date: 2013-06-09
    Description: In the companion Paper XV of this series, we derive accurate total mass-to-light ratios $(\rm M/L)_{\rm JAM}\approx ({\rm M/L})({\it r}= {R_{\rm e}})$ within a sphere of radius $r= {R_{\rm e}}$ centred on the galaxy, as well as stellar (M/L) stars (with the dark matter removed) for the volume-limited and nearly mass-selected (stellar mass $M_\star \gtrsim 6\times 10^9 {\,\mathrm{M}_{\odot }}$ ) ATLAS 3D sample of 260 early-type galaxies (ETGs, ellipticals Es and lenticulars S0s). Here, we use those parameters to study the two orthogonal projections $({M_{\rm JAM}}, {\sigma _{\rm e}})$ and $({M_{\rm JAM}}, {R_{\rm e}^{\rm maj}})$ of the thin Mass Plane (MP) $({M_{\rm JAM}}, {\sigma _{\rm e}}, {R_{\rm e}^{\rm maj}})$ which describes the distribution of the galaxy population, where $ {M_{\rm JAM}}\equiv L\times ({\rm M/L})_{\rm JAM}\approx M_\star$ . The distribution of galaxy properties on both projections of the MP is characterized by: (i) the same zone of exclusion (ZOE), which can be transformed from one projection to the other using the scalar virial equation. The ZOE is roughly described by two power laws, joined by a break at a characteristic mass $ {M_{\rm JAM}}\approx 3\times 10^{10} {\,\mathrm{M}_{\odot }}$ , which corresponds to the minimum R e and maximum stellar density. This results in a break in the mean $ {M_{\rm JAM}}\text{--} {\sigma _{\rm e}}$ relation with trends $ {M_{\rm JAM}}\propto \sigma _{\rm e}^{2.3}$ and $ {M_{\rm JAM}}\propto \sigma _{\rm e}^{4.7}$ at small and large e , respectively; (ii) a characteristic mass $ {M_{\rm JAM}}\approx 2\times 10^{11} {\,\mathrm{M}_{\odot }}$ which separates a population dominated by flat fast rotator with discs and spiral galaxies at lower masses, from one dominated by quite round slow rotators at larger masses; (iii) below that mass the distribution of ETGs’ properties on the two projections of the MP tends to be constant along lines of roughly constant e , or equivalently along lines with $ {R_{\rm e}^{\rm maj}}\propto {M_{\rm JAM}}$ , respectively (or even better parallel to the ZOE: $ {R_{\rm e}^{\rm maj}}\propto M_{\rm JAM}^{0.75}$ ); (iv) it forms a continuous and parallel sequence with the distribution of spiral galaxies; (v) at even lower masses, the distribution of fast-rotator ETGs and late spirals naturally extends to that of dwarf ETGs (Sph) and dwarf irregulars (Im), respectively. We use dynamical models to analyse our kinematic maps. We show that e traces the bulge fraction, which appears to be the main driver for the observed trends in the dynamical (M/L) JAM and in indicators of the (M/L) pop of the stellar population like Hβ and colour, as well as in the molecular gas fraction. A similar variation along contours of e is also observed for the mass normalization of the stellar initial mass function (IMF), which was recently shown to vary systematically within the ETGs’ population. Our preferred relation has the form $\log _{10} [({\rm M/L})_{\rm stars}/({\rm M/L})_{\rm Salp}]=a+b\times \log _{10}({\sigma _{\rm e}}/130\, {km s^{-1}})$ with a  = –0.12 ± 0.01 and b  = 0.35 ± 0.06. Unless there are major flaws in all stellar population models, this trend implies a transition of the mean IMF from Kroupa to Salpeter in the interval $\log _{10}({\sigma _{\rm e}}/{\rm km\, s}^{-1})\approx 1.9\text{--}2.5$ (or $ {\sigma _{\rm e}}\approx 90\text{--}290$ km s –1 ), with a smooth variation in between, consistently with what was shown in Cappellari et al. The observed distribution of galaxy properties on the MP provides a clean and novel view for a number of previously reported trends, which constitute special two-dimensional projections of the more general four-dimensional parameters trends on the MP. We interpret it as due to a combination of two main effects: (i) an increase of the bulge fraction, which increases e , decreases R e , and greatly enhance the likelihood for a galaxy to have its star formation quenched, and (ii) dry merging, increasing galaxy mass and R e by moving galaxies along lines of roughly constant e (or steeper), while leaving the population nearly unchanged.
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  • 10
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    The ATLAS3D project - XXI. Correlations between gradients of local escape velocity and stellar populations in early-type galaxies (2013)
    Oxford University Press
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    Publication Date: 2013-06-09
    Description: We explore the connection between the local escape velocity, V esc , and the stellar population properties in the ATLAS 3D survey, a complete, volume-limited sample of nearby early-type galaxies. We make use of ugriz photometry to construct Multi-Gaussian Expansion models of the surface brightnesses of our galaxies. We are able to fit the full range of surface brightness profiles found in our sample, and in addition we reproduce the results of state-of-the-art photometry in the literature with residuals of 0.04 mag. We utilize these photometric models and SAURON integral-field spectroscopy, combined with Jeans dynamical modelling, to determine the local V esc derived from the surface brightness. We find that the local V esc is tightly correlated with the Mg b and Fe5015 line strengths and optical colours, and anti-correlated with the Hβ line strength. In the case of the Mg b and colour– V esc relations we find that the relation within individual galaxies follows the global relation between different galaxies. We intentionally ignored any uncertain contribution due to dark matter since we are seeking an empirical description of stellar population gradients in early-type galaxies that is ideal for quantitative comparison with model predictions. We also make use of single stellar population (SSP) modelling to transform our line strength index measurements into the SSP-equivalent parameters age ( t ), metallicity ([Z/H]) and α-enhancement [α/Fe]. The residuals from the relation are correlated with age, [α/Fe], molecular gas mass and local environmental density. We identify a population of galaxies that occur only at low V esc that exhibit negative gradients in the Mg b – and Colour– V esc relations. These galaxies typically have young central stellar populations and contain significant amounts of molecular gas and dust. Combining these results with N -body simulations of binary mergers we use the Mg b – V esc relation to constrain the possible number of dry mergers experienced by the local early-type galaxy population – a typical massive early-type galaxy can have experienced only ~1.5 major mergers before becoming a significant outlier in the Mg b – V esc relation.
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    Topics: Physics
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