Incidence of Mg II absorption systems toward flat-spectrum radio quasars.
CHAND H. and GOPAL-KRISHNA
Abstract (from CDS):
The conventional wisdom that the rate of incidence of Mg II absorption systems, dN/dz (excluding "associated systems" having a velocity βc relative to the active galactic nucleus (AGN) of less than ∼5000 km/s), is totally independent of the background AGNs has been challenged by a recent finding that dN/dz for strong Mg II absorption systems toward distant blazars is 2.2±0.80.6 times the value known for normal optically selected quasars (QSOs). This has led to the suggestion that a significant fraction of even the absorption systems with β as high as ∼0.1 may have been ejected by the relativistic jets in the blazars, which are expected to be pointed close to our direction. Here, we investigate this scenario using a large sample of 115 flat-spectrum radio-loud quasars (FSRQs) that also possess powerful jets, but are only weakly polarized. We show, for the first time, that dN/dz toward FSRQs is, on the whole, quite similar to that known for QSOs and that the comparative excess of strong Mg II absorption systems seen toward blazars is mainly confined to β < 0.15. The excess relative to FSRQs probably results from a likely closer alignment of blazar jets with our direction; hence, any gas clouds accelerated by them are more likely to be on the line of sight to the active quasar nucleus.
BL Lacertae objects: general - galaxies: jets - intergalactic medium - quasars: absorption lines - quasars: general - techniques: spectroscopic
VizieR on-line data:
<Available at CDS (J/ApJ/754/38): table2.dat table3.dat>