1201.1286 (C. -A. Faucher-Giguere)
C. -A. Faucher-Giguere
Photoionization modeling of certain low-ionization broad absorption lines in
quasars implies very compact (Delta R~0.01 pc), galaxy-scale (R kpc) absorbers
blueshifted by several 1000 km s^-1. While these are likely signatures of
quasar outflows, the lifetimes of such compact absorbers are too short for them
to be direct ejecta from a nuclear wind. Instead, I argue that the absorbing
clouds must be transient and created in situ. Following arguments detailed by
Faucher-Giguere, Quataert, & Murray (2011), I show that a model in which the
cool absorbers form in radiative shocks arising when a quasar blast wave
impacts an interstellar cloud along the line of sight successfully explains the
key observed properties. Using this radiative shock model, the outflow kinetic
luminosities for three luminous quasars are estimated to be Edot,k~2-5% L_AGN
(with corresponding momentum fluxes Pdot~2-15 L_AGN/c), consistent with
feedback models of the M-sigma relation. These energetics are similar to those
recently inferred of molecular outflows in local ultra-luminous infrared
galaxies and in post-starburt winds, suggesting that active galactic nuclei
(AGN) are capable of driving such outflows. Radiative shocks probably affect
the multiphase structure of outflows in a range of other systems, including
narrower and higher-ionization quasar absorption lines, and compact
intergalactic absorbers ejected by star formation and AGN activity.
View original:
http://arxiv.org/abs/1201.1286
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