AAS 203rd Meeting, January 2004
Session 26 Galaxy Evolution
Oral, Monday, January 5, 2004, 10:00-11:30am, Regency VII

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[26.04] Analogs of Weak MgII Absorbers in the Present Day Universe

J. C. Charlton, A. Narayanan, J. Ding (Penn State)

Single-cloud weak MgII absorbers trace small pockets of material (~10pc) that reside outside of large galaxies. They have close to solar metallicity, despite their lack of luminous hosts. They could arise as fragments of metal-rich debris in an abundant population of faint dwarf galaxies or their remnant superwinds, or they could arise in intergalactic star clusters formed at high redshift. The typical single-cloud weak MgII absorber at redshift one has coincident CIV absorption, but the CIV profiles are too strong and too broad for CIV to arise in the same phase as the MgII.

We have completed a survey of the high-resolution database of HST/STIS ultra-violet Echelle spectra of quasars. We have searched for the low redshift analogs to single-cloud weak MgII absorbers, traced by the combination of CII and SiII absorption, and we have discovered a few at redshift 0 to 0.2. We will compare the inferred physical properties (phase structure, densities, metallicities) of these low redshift absorbers to the weak MgII absorbers we have studied at z~1. To guide our thinking on the evolution we have conducted simulations of how the absorbers would evolve because of the rapidly diminishing extragalactic background radiation over that redshift interval. As one might expect, the weak MgII absorbers would systematically become stronger, and their CIV phases would become less prominent.

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

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Bulletin of the American Astronomical Society, 35#5
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