AAS 200th meeting, Albuquerque, NM, June 2002
Session 40. Evolution of Galaxies, Galaxy Surveys, IGM
Display, Tuesday, June 4, 2002, 10:00am-6:30pm, SW Exhibit Hall

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[40.01] The Ages of Early-Type Galaxies at Redshifts of z~1-2

M. J. Wolf, K. Gebhardt (Univ. of Texas at Austin), G. J. Hill (McDonald Observatory / Univ. of Texas at Austin)

Recent evolutionary studies of the Fundamental Plane and the luminosity function suggest assemblage of early-type galaxies in the field around z = 2. However, standard techniques for studying galaxies at this epoch suffer from their spectral probes being redshifted out of the observable optical band. We utilize a technique for estimating the ages of early-type galaxies at redshifts of z ~ 1-2 by studying their rest-frame UV spectra, observable at optical wavelengths. Two spectral breaks in the range from 2200-3000 Å have previously been investigated as age discriminators on only a few galaxies. We will significantly increase this number.

Spectroscopy for this project is being obtained with the 9-m Hobby-Eberly Telescope. The HET Low Resolution Spectrograph Multi-object Spectroscopy Unit (LRS-MOS) uses movable slitlets, which provide accurate relative flux calibration over multiple observations on the same field. Wavelength coverage in one LRS setup covers both the rest UV and the 4000 Å break region for galaxies near z = 1. A J-band extension to the LRS will come online later this year, allowing observations of the standard features used for age estimation on galaxies at 1 < z < 2.

The HET sample will be complimented with the rest UV spectra of approximately 50 galaxies from the Deep Extragalactic Evolutionary Probe (DEEP) survey. Ages of the galaxies deduced from the UV features will be compared to those from other means, providing a calibration of this technique. Once the HET spectra are obtained and ages are determined, for these apparently young (< 4 Gyr) galaxies, we will be able to break the age-metallicity degeneracy inherent to the evolutionary models.

This work is partially funded by NASA GSRP fellowship grant NGT5-50301.

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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.