Fundamental differences in the radio properties of red and blue quasars: evolution strongly favoured over orientation
Abstract
A minority of the optically selected quasar population are red at optical wavelengths due to the presence of dust along the line of sight. A key focus of many red quasar studies is to understand their relationship with the overall quasar population: are they blue quasars observed at a (slight) inclination angle or do they represent a transitional phase in the evolution of quasars? Identifying fundamental differences between red and blue quasars is key to discriminate between these two paradigms. To robustly explore this, we have uniformly selected quasars from the Sloan Digital Sky Survey with mid-infrared counterparts, carefully controlling for luminosity and redshift effects. We take a novel approach to distinguish between colour-selected quasars in the redshift range of 0.2 < z < 2.4 by constructing redshift-sensitive g* − i* colour cuts. From cross-matching this sample to the Faint Images of the Radio Sky at Twenty-centimeters (FIRST) survey, we have found a factor ≈ 3 larger fraction of radio-detected red quasars with respect to that of blue quasars. Through a visual inspection of the FIRST images and an assessment of the radio luminosities (rest-frame ${L_{\rm 1.4\, GHz}}$ and ${L_{\rm 1.4\, GHz}}/{L_{\rm 6\mu m}}$), we find that the radio-detection excess for red quasars is primarily due to compact and radio-faint systems (around the radio-quiet – radio-loud threshold). We show that our results rule out orientation as the origin for the differences between red and blue quasars and argue that they provide broad agreement with an evolutionary model.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jul 01, 2019
- Source ID
- 10.1093/mnras/stz1771
Entities
People
- David M. Alexander
- David Rosario
- Elisabeta Lusso
- Lizelke Klindt
- Sotiria Fotopoulou
Organizations
- Alfred P. Sloan Foundation
- American Museum of Natural History
- California Institute of Technology
- Carle Foundation Hospital
- Case Western Reserve University
- Chinese Academy of Sciences
- Drexel University
- Durham University
- Higher Education Funding Council for England
- Institute for Advanced Study
- Jet Propulsion Laboratory
- Johns Hopkins University
- Los Alamos National Laboratory
- Max Planck Society
- National Aeronautics and Space Administration
- National Science Foundation
- New Mexico State University
- Ohio State University
- Princeton University
- Science and Technology Facilities Council
- Swiss National Science Foundation
- United States Department of Energy
- United States Naval Observatory
- University of Basel
- University of California
- University of Cambridge
- University of Chicago
- University of Pittsburgh
- University of Portsmouth
- University of Washington