[113.07] The Nature of Low redshift Damped Lyman Alpha Systems

AAS 203rd Meeting, January 2004
Session 113 Molecules and Atoms at High Z and Low Z
Poster, Thursday, January 8, 2004, 9:20am-4:00pm, Grand Hall

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[113.07] The Nature of Low redshift Damped Lyman Alpha Systems

T. C. Urrutia (UC Davis, IGPP LLNL), M. Lacy (SIRTF Science Center), R. H. Becker (UC Davis, IGPP LLNL), L. J. Storrie-Lombardi (SIRTF Science Center), M. D. Gregg (UC Davis, IGPP LLNL)

We present results of an ongoing campaign to discover damped Ly\alpha (DLA) absorption systems at redshifts z < 1.5. We selected quasar absorption systems from the FIRST Bright Quasar Survey with equivalent widths for FEII 2600 > 1 Å and took follow-up spectra of some of these with the Hubble Space Telescope (HST). So far, 6 new low redshift DLAs have been discovered in spectra of 21 candidate absorption systems. This is fewer than predicted by previous studies (Rao & Turnshek 2000). Nevertheless, all of our systems show a column density N_HI \ge 10¹⁹ cm^-2.

We have made different high resolution composite spectra of 45 possible DLAs, revealing much weaker absorption lines. Metallicity measurements in the composite spectra show that the cosmic neutral gas-phase metallicity traced by the DLAs is larger at lower redshift.

We have also identified galaxies near 5 quasars which are at the redshift of DLA systems of the quasars. The spectra suggest that these are star forming galaxies and they have a mean luminosity lower than the break in the local galaxy luminosity function (sub-L^*).

This work is supported under grant AST-00-98355 from the NSF.

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