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Date and Time of the Query: 2019-08-22 T12:12:53 PDT
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For refcode 1997ApJ...481L..19G:
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1997ApJ...481L..19G Line-Strength Indices in Bright Spheroidal Galaxies: Evidence for a Stellar Population Dichotomy between Spheroidal and Elliptical Galaxies JAVIER GORGAS, SANTOS PEDRAZ, RAFAEL GUZMAN, NICOLAS CARDIEL, J. JESUS GONZALEZ Received 1996 November 13; accepted 1997 March 3 ABSTRACT We present new measurements of central line-strength indices (namely, Mg_2_, <Fe>, and H{beta}) and gradients for a sample of six bright spheroidal (Sph) galaxies in the Virgo Cluster. Comparison with similar measurements for elliptical (E) galaxies, galactic globular clusters (GGCs), and stellar population models yield the following results: (1) in contrast with bright E galaxies, bright Sph galaxies are consistent with solar abundance [Mg/Fe] ratios; (2) bright Sph galaxies exhibit metallicities ranging from values typical for metal-rich GGCs to those for E galaxies; (3) although absolute mean ages are quite model dependent, we find evidence that the stellar populations of some (if not all) Sph galaxies look significantly younger than GGCs; and (4) Mg_2_ gradients of bright Sph galaxies are significantly shallower than those of E galaxies. We conclude that the dichotomy found in the structural properties of Sph and E galaxies is also observed in their stellar populations. A tentative interpretation in terms of differences in star formation histories is suggested. Subject headings: galaxies: abundances-galaxies: evolution-galaxies: stellar content
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