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Session 51 - Galaxy Evolution and the Intergalactic Medium.
Display session, Wednesday, June 10
We have been able to form a fairly complete picture of the galaxy responsible for the z_a=0.395 absorption line system in PKS 1229--021 by combining Keck HIRES and LRIS spectroscopy with observations taken with the Hubble Space Telescope. The image of the absorber is consistent with the inclined disk of a moderately luminous spiral galaxy. We have not been able to detect the continuum from this galaxy spectroscopically, but our LRIS spectra show emission from [O II] \lambda3727 which can be interpreted to be indicative of star formation at the rate of a few M_\sun per year. The HIRES spectra clearly show an ``edge--leading'' absorption profile. Prochaska and Wolfe have predicted that the velocity of the center of mass of the absorbing galaxy should fall near one edge of the absorption profile if the damped Ly\alpha systems are due to the rotating disks of spiral galaxies. The [O II] emission velocity is consistent with this, but there is some ambiguity due to the doublet nature of the [O II] emission. Although the absorption lines of the abundant elements are saturated in the components which correspond to the H I absorption, we have been able to measure accurate column densities for Ca II, Ti II, and Mn II for comparison with the H I column density determined from low resolution HST/FOS spectra. The abundances are compatible with approximately 0.1 of solar, with little or no dust, but they are also consistent with lines of sight toward \zeta Oph through warm interstellar clouds.
HIRES observations of the z_a=0.692 absorption line system in 3CR 286 will also be discussed, after the data are fully analyzed.
This work is part of the Goddard High Resolution Spectrograph Guaranteed Time Observations and is supported by NASA grant NAG5--1858 and the NSF.
Program listing for Wednesday