NASA/IPAC EXTRAGALACTIC DATABASE
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For refcode 1998AJ....116...85S:
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1998AJ....116...85S THE AGES OF DISTURBED FIELD ELLIPTICAL GALAXIES. I. GLOBAL PROPERTIES DAVID R. SILVA European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching, Germany; dsilva@eso.org AND GREGORY D. BOTHUN Department of Physics, University of Oregon, 120 Willamette Hall, Eugene, OR 97403; nuts@moo.uoregon.edu Received 1997 May 21; revised 1998 February 17 ABSTRACT Near-infrared images of elliptical galaxies with morphological signatures of recent merger activity have been obtained. If this merger activity stimulated significant and distributed star formation within the region defined by R < 1.5R_e_, then JHK photometry in this region should detect the presence of an intermediate-age stellar population associated with this event. Our observations, however, show that these galaxies occupy the same locus of points in the J - H versus H - K plane as elliptical galaxies with no signs of recent merger activity. This strongly constrains the global fractional amount of intermediate-age (1-3 Gyr) stellar mass to be no more than 10%-15%, and in most cases the data are consistent with all the stellar mass being old (T > 10 Gyr) and metal-rich ([Fe/H] >= -0.3). We argue that any recent merger activity was, therefore, not accompanied by a significant episode of distributed star formation within the region defined by R < 1.5R_e_ and that the bluer UBV colors often observed in this region for some of these galaxies are due to the accretion of lower mass companions or relative abundance differences. The possibility of a strongly centralized starburst resulting from the merger, instead of a more distributed star-forming episode, is fully discussed in Paper II of this series, in which similar tight constraints on this activity will be discussed. Key words: galaxies: elliptical and lenticular, cD-galaxies: evolution- galaxies: formation-galaxies: stellar content -galaxies: structure
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