How Are Red and Blue Quasars Different? The Radio Properties

Abstract

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.

Powerful Radio-loud Quasars Are Triggered by Galaxy Mergers in the Cosmic Bright Ages

“…However, in Figure 9 we also show rest-frame G 29 -I quasar colors (with effective wavelengths of 477 and 762.5 nm for the G and I bands, respectively) determined following the same methodology as our rest-frame U − V colors (outlined in Section 2). The sharp peak in the G − I bin [0.5, 1] is consistent with the findings from recent color studies of local quasars with the middle 50% of the SDSS g * − i * color distribution in the same 0.5-1 range (Fawcett et al 2021). Our Glikman et al (2006) near-infrared optical quasar template has a G − I color ∼0.2, but the authors acknowledge the small bias of a bluer continuum from this template than the SDSS DR1 quasar composite spectrum from Vanden Berk et al (2001).…”

New Window on the Radio Emission from Galaxies, Clusters and Cosmic Web—Conference Summary

“…Victoria Fawcett summarized recent works where they analyzed the radio properties of SDSS optically selected red quasars and presented new results obtained using four radio surveys: FIRST, VLA Stripe 82, VLA COSMOS 3 GHz and LoTSS DR1. They suggested that the observed radio emission properties of red quasars can be explained by small-scale synchrotron jets, frustrated jets or dusty winds interacting with the interstellar medium [29].…”