BAL and non-BAL quasars: continuum, emission and absorption properties
  establish a common parent sample
  Using a sample of $\simeq$144,000 quasars from the Sloan Digital Sky Survey
data release 14 we investigate the outflow properties, evident both in
absorption and emission, of high-ionization Broad Absorption Line (BAL) and
non-BAL quasars with redshifts 1.6 $\lesssim z \leq$ 3.5 and luminosities 45.3
$< \log_{10}(L_{bol}) < $ 48.2 erg s$^{-1}$. Key to the investigation is a
continuum and emission-line reconstruction scheme, based on mean-field
independent component analysis, that allows the kinematic properties of the
CIV$\lambda$1550 emission line to be compared directly for both non-BAL and BAL
quasars. CIV-emission blueshift and equivalent-width (EW) measurements are thus
available for both populations. Comparisons of the emission-line and BAL-trough
properties reveal strong systematic correlations between the emission and
absorption properties. The dependence of quantitative outflow indicators on
physical properties such as quasar luminosity and luminosity relative to
Eddington-luminosity are also shown to be essentially identical for the BAL and
non-BAL populations. There is an absence of BALs in quasars with the hardest
spectral energy distributions (SEDs), revealed by the presence of strong
HeII$\lambda$1640 emission, large CIV$\lambda$1550-emission EW and no
measurable blueshift. In the remainder of the CIV-emission blueshift versus EW
space, BAL and non-BAL quasars are present at all locations; for every
BAL-quasar it is possible to identify non-BAL quasars with the same
emission-line outflow properties and SED-hardness. The co-location of BAL and
non-BAL quasars as a function of emission-line outflow and physical properties
is the key result of our investigation, demonstrating that (high-ionization)
BALs and non-BALs represent different views of the same underlying quasar
population.
