AAS 207th Meeting, 8-12 January 2006
Session 194 Galaxy Morphology and its Evolution
Oral, Thursday, 10:00-11:30am, January 12, 2006, Salon 1

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[194.04] An Infrared Investigation into the Formation of Elliptical Galaxies via Mergers

B. Rothberg (Space Telescope Science Institute), R. D. Joseph (Institute for Astronomy)

This dissertation presents the results of an infrared photometric and kinematic study of a sample of 51 optically selected merger remnants. The survey was conducted with the QUIRC infrared array on the University of Hawaii 2.2m telescope, and the ESI spectrograph on the 10m W.M. Keck-2 telescope. Deep K-band images were used to construct high-resolution surface brightness profiles, along with measurements of the photometric structural parameters and total luminosity. Spectroscopy of the Calcium triplet line at ~ 8500 Åwas used to measure the central velocity dispersion and to construct kinematic profiles. Most of the mergers in the sample have undergone partial or complete violent relaxation out to large spatial scales. The photometry also shows the first K-band detection of ``excess light'' in the surface brightness profiles of approximately one-third of the sample. The ``excess light'' may be the result of a starburst induced by the dissipative collapse of gas. The structural parameters show that a majority of the mergers have disky isophotal shapes. The luminosity of the mergers are equal to, or greater than an L* elliptical galaxy, in contrast to several earlier studies. The central velocity dispersions of a sub-sample of 38 mergers indicate that most of these objects have central kinematic properties consistent with intermediate- to giant-mass ellipticals, also in contrast to several earlier studies. Correlations between photometric and kinematic properties have also been analyzed. The results show a strong correlation among Fundamental Plane parameters. Some mergers lie slightly offset from the plane, but in a direction consistent with photometric evolution onto the plane. The results further suggest that only photometric differences due to luminosity exist between mergers and ellipticals, consistent with a picture of star-formation and/or younger stellar populations. Indications also suggest that velocity dispersions measured with the CO absorption line are smaller than those measured with the Calcium triplet. The kinematic profiles reveal the first ever detection of counter-rotating cores in mergers. A majority of the mergers appear to be fast rotators, while the rest show an apparent cutoff at low values of V/\sigma.

The author(s) of this abstract have provided an email address for comments about the abstract: rothberg@stsci.edu

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