Other
Scientific paper
Jan 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21541134c&link_type=abstract
American Astronomical Society, AAS Meeting #215, #411.34; Bulletin of the American Astronomical Society, Vol. 42, p.245
Other
Scientific paper
Broad absorption lines (BALs) in quasar spectra identify high velocity outflows that likely exist in all quasars and could play a major role in feedback to galaxy evolution. Studying the variability in these BALs can help us understand the structure, evolution, and basic physical properties of these outflows. We are conducting the largest-ever BAL monitoring program with more than 120 spectra of 25 luminous quasars at z˜1.8-2.8, covering time scales from 19 days to 7.7 years in the quasar rest-frame. We investigate changes in the CIV 1550A BALs, and we see a variety of phenomena, including some BALs that either appeared or disappeared completely and other BALs that did not change at all over the whole observation period. Here we present some results from this ongoing program. The incidence of variability declines from ˜70% to ˜40% between the time domains of several years and a few months. Typically, only portions of the BAL troughs vary. We find that BALs at higher velocities are more likely to vary than those at lower velocities and that weaker BALs (or the weaker portions of a BAL) are more likely to vary than stronger BALs. We also find that the fractional change in BAL strength correlates with the strength of the BAL feature, but not with the outflow velocity. We will present new results on comparing variability in the CIV 1550A BAL to the SiIV 1400A BAL to help distinguish between moving clouds and ionization changes as the cause of the variability. We also investigate the timescales of variability to help define the actual timescales, the causes of the variability, and the sizes, locations, and volatility of the outflowing gas.
Barlow Thomas A.
Capellupo Daniel M.
Hamann Fred
Shields Joseph C.
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