The ATLAS(3D) project: XXI. Correlations between gradients of local escape velocity and stellar populations in early-type galaxies

Nicholas Scott*, Michele Cappellari, Roger L. Davies, Gijs Verdoes Kleijn, Maxime Bois, Katherine Alatalo, Leo Blitz, Frederic Bournaud, Martin Bureau, Alison Crocker, Timothy A. Davis, P. T. de Zeeuw, Pierre-Alain Duc, Eric Emsellem, Sadegh Khochfar, Davor Krajnovic, Harald Kuntschner, Richard M. McDermid, Raffaella Morganti, Thorsten NaabTom Oosterloo, Marc Sarzi, Paolo Serra, Anne-Marie Weijmans, Lisa M. Young

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

57 Citations (Scopus)
264 Downloads (Pure)

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 H beta 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 similar to 1.5 major mergers before becoming a significant outlier in the Mg b-V-esc relation.

Original languageEnglish
Pages (from-to)1894-1913
Number of pages20
JournalMonthly Notices of the Royal Astronomical Society
Volume432
Issue number3
DOIs
Publication statusPublished - 1-Jul-2013

Keywords

  • galaxies: abundances
  • galaxies: elliptical and lenticular
  • cD
  • galaxies: evolution
  • galaxies: formation
  • DIGITAL SKY SURVEY
  • KINEMATICALLY DISTINCT CORES
  • MULTI-GAUSSIAN EXPANSION
  • VIRGO-CLUSTER SURVEY
  • LINE-STRENGTH MAPS
  • TO-LIGHT RATIO
  • SAURON PROJECT
  • ELLIPTIC GALAXIES
  • DATA RELEASE
  • MAGNITUDE RELATION

Cite this