Quasars That Have Transitioned from Radio-quiet to Radio-loud on Decadal Timescales Revealed by VLASS and FIRST

Kristina Nyland, Dillon Z. Dong, Pallavi Patil, Mark Lacy, Sjoert Van Velzen, Amy E. Kimball, Sumit K. Sarbadhicary, Gregg Hallinan, Vivienne Baldassare, Tracy E. Clarke, Andy D. Goulding, Jenny Greene, Andrew Hughes, Namir Kassim, Magdalena Kunert-Bajraszewska, Thomas J. MacCarone, Kunal Mooley, Dipanjan Mukherjee, Wendy Peters, Leonid PetrovEmil Polisensky, Wiphu Rujopakarn, Mark Whittle, Mattia Vaccari

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12 Scopus citations

Abstract

We have performed a search over 3440 deg2 of Epoch 1 (2017-2019) of the Very Large Array Sky Survey to identify unobscured quasars in the optical (0.2 < z < 3.2) and obscured active galactic nuclei (AGNs) in the infrared that have brightened dramatically in the radio over the past one to two decades. These sources would have been previously classified as "radio-quiet"quasars based on upper limits from the Faint Images of the Radio Sky at Twenty cm survey (1993-2011), but they are now consistent with "radio-loud"quasars (). A quasi-simultaneous, multiband (∼1-18 GHz) follow-up study of 14 sources with the VLA has revealed compact sources (<0.″1 or <1 kpc) with peaked radio spectral shapes. The high-amplitude variability over decadal timescales at 1.5 GHz (100% to >2500%) but roughly steady fluxes over a few months at 3 GHz are inconsistent with extrinsic variability due to propagation effects, thus favoring an intrinsic origin. We conclude that our sources are powerful quasars hosting compact/young jets. This challenges the generally accepted idea that "radio-loudness"is a property of the quasar/AGN population that remains fixed on human timescales. Our study suggests that frequent episodes of short-lived AGN jets that do not necessarily grow to large scales may be common at high redshift. We speculate that intermittent but powerful jets on subgalactic scales could interact with the interstellar medium, possibly driving feedback capable of influencing galaxy evolution.

Original languageEnglish (US)
Article number74
JournalAstrophysical Journal
Volume905
Issue number1
DOIs
StatePublished - Dec 10 2020

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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