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Preprint typeset using LATEX style emulateapj v. 10/09/06 THE DYNAMICAL DISTINCTION BETWEEN ELLIPTICAL AND LENTICULAR GALAXIES IN DISTANT CLUSTERS: FURTHER EVIDENCE FOR THE RECENT ORIGIN OF S0 GALAXIES

By Sean M. Moran, Boon Liang Loh, Richard S. Ellis, Tommaso Treu, Kevin Bundy and Lauren A. Macarthur

Abstract

We examine resolved spectroscopic data obtained with the Keck II telescope for 44 spheroidal galaxies in the fields of two rich clusters, Cl0024+16 (z=0.40) and MS0451-03 (z=0.54), and contrast this with similar data for 23 galaxies within the redshift interval 0.3< z <0.65 in the GOODS northern field. For each galaxy we examine the case for systemic rotation, derive central stellar velocity dispersions σ and photometric ellipticities, ǫ. Using morphological classifications obtained via Hubble Space Telescope imaging as the basis, we explore the utility of our kinematic quantities in distinguishing between pressure-supported ellipticals and rotationallysupported lenticulars (S0s). We demonstrate the reliability of using the v/(1 −ǫ) vs σ and v/σ vs ǫ distributions as discriminators and further test these diagnostics using equivalent local data in the Coma cluster. According to our tests, both discriminators are reliable at at least the 70-85 % level and limited by the accuracy of the morphological typing. Using our classifiers we then examine the morphology-density relation for elliptical and S0 galaxies separately at a mean redshift of z ≃0.5 confirming, from kinematic data alone, the recent growth of rotationally-supported spheroidals. We discuss the feasibility of extending the method to a more comprehensive study of cluster and field galaxies to z ≃1, in order to verify in detail the recent density-dependent growth o

Year: 2008
OAI identifier: oai:CiteSeerX.psu:10.1.1.317.9056
Provided by: CiteSeerX
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