Viewing angle observations and effects of evolution with redshift, black
  hole mass, and Eddington ratio in quasar based cosmology
  This study is focused on the observational measurement of the viewing angle
of individual quasars by modeling the broadband quasar spectrum ranging from
the infra-red (IR) to the soft X-ray band. Sources are selected from various
published catalogs, and their broadband quasi-simultaneous spectral data points
were collected and used to model. We started with a COSMOS sample of type-1
sources which have broadband photometric points. Then, to include more data
points, we cross-matched the COSMOS with the SDSS DR14 quasar catalog, and
eventually, we find 90 sources that have broadband data ranging from IR to soft
X-ray. The broadband spectral energy distribution (SED) modeling is done in
Xspec by using the optxagnf and the SKIRTOR models for the X-ray, UV, Optical,
and IR regimes for each source. The whole sample is divided into four bins with
respect to redshift, black hole (BH) mass, and Eddington ratio with an equal
number of sources in each bin. The viewing angle is estimated in each bin, and
its evolution with respect to redshift, BH mass, and Eddington ratio is
examined. As a result, we did not find any significant evolution of viewing
angle with those parameters within the 95$\%$ confidence interval. We conclude
that the use of quasars in cosmology to determine the expansion rate of the
universe is therefore justified, and biases are not expected.
