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How Are Red and Blue Quasars Different? The Radio Properties

Fawcett, Victoria A.; Alexander, David M.; Rosario, David J.; Klindt, Lizelke

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Victoria A. Fawcett

David J. Rosario

Lizelke Klindt


A non-negligible fraction of quasars are red at optical wavelengths, indicating (in the majority of cases) that the accretion disc is obscured by a column of dust which extinguishes the shorter-wavelength blue emission. In this paper, we summarize recent work by our group, where we find fundamental differences in the radio properties of SDSS optically-selected red quasars. We also present new analyses, using a consistent color-selected quasar parent sample matched to four radio surveys (FIRST, VLA Stripe 82, VLA COSMOS 3 GHz, and LoTSS DR1) across a frequency range 144 MHz–3 GHz and four orders of magnitude in radio flux. We show that red quasars have enhanced small-scale radio emission (∼kpc) that peaks around the radio-quiet threshold (defined as the ratio of 1.4 GHz luminosity to 6 μm luminosity) across the four radio samples. Exploring the potential mechanisms behind this enhancement, we rule out star-formation and propose either small-scale synchrotron jets, frustrated jets, or dusty winds interacting with the interstellar medium; the latter two scenarios would provide a more direct connection between opacity (dust; gas) and the production of the radio emission. In our future study, using new multi-band uGMRT data, we aim to robustly distinguish between these scenarios.


Fawcett, V. A., Alexander, D. M., Rosario, D. J., & Klindt, L. (2021). How Are Red and Blue Quasars Different? The Radio Properties. Galaxies, 9(4), Article 107.

Journal Article Type Article
Acceptance Date Nov 16, 2021
Online Publication Date Nov 19, 2021
Publication Date 2021
Deposit Date Dec 8, 2021
Publicly Available Date Dec 8, 2021
Journal Galaxies
Electronic ISSN 2075-4434
Publisher MDPI
Peer Reviewed Peer Reviewed
Volume 9
Issue 4
Article Number 107
Public URL


Published Journal Article (1.5 Mb)

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Copyright Statement
© 2021 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://

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