Viewing angle observations and effects of evolution with redshift, black hole mass, and Eddington ratio in quasar based cosmology

TL;DR

This study models the broadband spectra of quasars to measure their viewing angles and investigates their evolution with redshift, black hole mass, and Eddington ratio, finding no significant evolution within confidence limits.

Contribution

It provides the first systematic analysis of quasar viewing angles across different redshifts and black hole properties using broadband spectral modeling.

Findings

No significant evolution of viewing angle with redshift, BH mass, or Eddington ratio

Supports the use of quasars as unbiased cosmological probes

Broadband spectral modeling effectively estimates quasar viewing angles

Abstract

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.