Variability Constraints on Quasar Broad Absorption Line Outflows

Details Variability Constraints on Quasar Broad Absorption Line Outflows Variability Constraints on Quasar Broad Absorption Line Outflows

Jan 2012

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012aas...21910907c&link_type=abstract

American Astronomical Society, AAS Meeting #219, #109.07

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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 a BAL monitoring program, which so far includes 163 spectra of 24 luminous quasars at z=1.2-2.9, covering time-scales from 1 week to 8 years in the quasar rest-frame. We investigate changes in both the CIV BALs and the SiIV BALs, and we see a variety of phenomena, including some BALs with dramatic variability over a wide range in outflow velocities and other BALs that did not change at all over the entire observation period. Variability generally occurred in only portions of BAL troughs. The fraction of quasars with CIV BAL variability increased as we added more observing epochs to our sample, with 88% of the quasars showing CIV BAL variability. When comparing CIV to SiIV BAL variability, we found that SiIV BALs are more likely to vary than CIV BALs. When both the CIV and SiIV BALs vary within the same quasar, they always vary in the same sense (with both lines either getting stronger or weaker). We have new data that probe the shortest time-scales (<1 month rest-frame), which provide constraints on the sizes and location of the outflowing gas. We also present some preliminary results on the study of key diagnostic lines, such as PV λ1118, 1128. Studying these lines provides crucial constraints on the total column densities in the flows, which we can then use to estimate their mass outflow rates and kinetic energy yields. These quantities will help determine the viability of these outflows as a feedback mechanism.

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