A variable P舁v broad absorption line and quasar outflow energetics

Abstract

Broad absorption lines (BALs) in quasar spectra identify high velocity\noutflows that might exist in all quasars and could play a major role in\nfeedback to galaxy evolution. The viability of BAL outflows as a feedback\nmechanism depends on their kinetic energies, as derived from the outflow\nvelocities, column densities, and distances from the central quasar. We\nestimate these quantities for the quasar, Q1413+1143 (redshift $z_e = 2.56$),\naided by the first detection of PV $\\lambda\\lambda$1118,1128 BAL variability in\na quasar. In particular, PV absorption at velocities where the CIV trough does\nnot reach zero intensity implies that the CIV BAL is saturated and the absorber\nonly partially covers the background continuum source (with characteristic size\n<0.01 pc). With the assumption of solar abundances, we estimate that the total\ncolumn density in the BAL outflow is log N_H > 22.3 (cm^-2). Variability in the\nPV and saturated CIV BALs strongly disfavors changes in the ionization as the\ncause of the BAL variability, but supports models with high-column density BAL\nclouds moving across our lines of sight. The observed variability time of 1.6\nyr in the quasar rest frame indicates crossing speeds >750 km/s and a radial\ndistance from the central black hole of <3.5 pc, if the crossing speeds are\nKeplerian. The total outflow mass is ~4100 M_solar, the kinetic energy ~4x10^54\nerg, and the ratio of the outflow kinetic energy luminosity to the quasar\nbolometric luminosity is ~0.02 (at the minimum column density and maximum\ndistance), which might be sufficient for important feedback to the quasar's\nhost galaxy.\n