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Probing quasar viewing angle with the variability structure function.
- Source :
-
Monthly Notices of the Royal Astronomical Society . Aug2023, Vol. 523 Issue 3, p4441-4454. 14p. - Publication Year :
- 2023
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Abstract
- Given the anisotropic emission from quasar accretion discs, their viewing angle affects estimates of the quasar luminosity, black hole mass, and Eddington ratio. Discs appear overluminous when viewed pole-on and underluminous when viewed at high inclination. In radio-quiet quasars, the viewing angle is usually unknown, although spectroscopic indicators have been proposed. Here, we use a recently discovered universality in the variability structure function (SF) of quasar light curves (LCs), where all quasars show the same SF when clocks run in units of orbital time-scale. As an offset from the mean relation can be caused by incorrect orbital time-scales and thus incorrect luminosities, we correlate these offsets with suggested inclination indicators. We derive SFs from NASA/Asteroid Terrestrial-impact Last Alert System (ATLAS) LCs spanning ∼6 yr of observation, using a sample of 183 luminous quasars with measured H β lines as well as 753 quasars with C iv and Mg ii lines. Starting from the proposed orientation indicators, we expect quasars with narrower H β lines and with more blueshifted C iv lines to be viewed more pole-on and thus appear overluminous. In contrast, our SF analysis finds that presumed pole-on discs appear underluminous, consistently for both line indicators. We discuss possible explanations for the behaviour of quasars with highly blueshifted C iv lines irrespective of inclination angle, including dusty outflows that might render the accretion disc underluminous and flatter disc temperature profiles with longer orbital time-scales than in thin-disc models but reach no satisfying conclusion. [ABSTRACT FROM AUTHOR]
- Subjects :
- *QUASARS
*ACCRETION disks
*LIGHT curves
*BLACK holes
*ANGLES
*ACTIVE galaxies
Subjects
Details
- Language :
- English
- ISSN :
- 00358711
- Volume :
- 523
- Issue :
- 3
- Database :
- Academic Search Index
- Journal :
- Monthly Notices of the Royal Astronomical Society
- Publication Type :
- Academic Journal
- Accession number :
- 164690017
- Full Text :
- https://doi.org/10.1093/mnras/stad1688