NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-03-24 T08:24:42 PDT
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For refcode 2013MNRAS.432.1894S:
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Copyright by Royal Astronomical Society. 2013MNRAS.432.1894S The ATLAS^3D^ project - XXI. Correlations between gradients of local escape velocity and stellar populations in early-type galaxies Scott, Nicholas; Cappellari, Michele; Davies, Roger L.; Kleijn, Gijs Verdoes; Bois, Maxime; Alatalo, Katherine; Blitz, Leo; Bournaud, Frederic; Bureau, Martin; Crocker, Alison; Davis, Timothy A.; de Zeeuw, P. T.; Duc, Pierre-Alain; Emsellem, Eric; Khochfar, Sadegh; Krajnovic, Davor; Kuntschner, Harald; McDermid, Richard M.; Morganti, Raffaella; Naab, Thorsten; Oosterloo, Tom; Sarzi, Marc; Serra, Paolo; Weijmans, Anne-Marie; Young, Lisa M. Abstract. 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 Hbeta 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 {alpha}-enhancement [{alpha}/Fe]. The residuals from the relation are correlated with age, [{alpha}/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. Key words: galaxies: abundances, galaxies: elliptical and lenticular, cD, galaxies: evolution, galaxies: formation
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