The dust, nebular emission and dependence on QSO radio properties of the
  associated Mg II absorption line systems
  We studied dust reddening and [O II] emission in 1730 Mg II associated
absorption systems (AAS; relative velocity with respect to QSOs, < 3000 km/s;
in units of velocity of light, \b{eta}, < 0.01) with 0.4 < z_abs < 2 in the
SDSS DR7, focusing on their dependence on the radio and other QSO properties.
We used control samples, several with matching radio properties to show (i) AAS
in radio detected (RD) QSOs cause 2.6 +/- 0.2 times higher dust extinction than
those in radio undetected (RUD) ones which, in turn, cause 2.9 +/- 0.7 times
the dust extinction in the intervening systems; (ii) AAS in core-dominated QSOs
cause 2.0 +/- 0.1 times higher dust extinction than in lobe-dominated QSOs;
(iii) occurrence of AAS is 2.1 +/- 0.2 times more likely in RD QSOs than in RUD
QSOs and 1.8 +/- 0.1 time more likely in QSOs having black holes with masses
larger than 1.23 x 10^{9} M_sun than in those with lower mass black holes; (iv)
there is excess flux in [O II]{\lambda}3727 emission in the composite spectra
of the AAS samples compared to those of the control samples, which is at the
emission redshift. Presence of AAS enhances the O II emission from the AGN
and/or the host galaxy. This excess is similar for both RD and RUD samples, and
is 2.5 +/- 0.4 times higher in lobe-dominated compared to core-dominated
samples. The excess depends on the black hole mass and Eddington ratio. All
these point to the intrinsic nature of the AAS except for the systems with
z_abs > z_em which could be infalling galaxies.
