Journal
ASTROPHYSICAL JOURNAL
Volume 905, Issue 1, Pages -Publisher
IOP Publishing Ltd
DOI: 10.3847/1538-4357/abc341
Keywords
Active galaxies; Radio sources; Galaxy evolution; Radio loud quasars; Quasars; Radio quiet quasars; Surveys; Radio active galactic nuclei; Radio astronomy; Radio jets; Radio transient sources; Extragalactic radio sources
Categories
Funding
- National Science Centre, Poland [2017/26/E/ST9/00216]
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We have performed a search over 3440 deg(2) 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 (L-3 GHz = 10(40-42) erg s(-1)). A quasi-simultaneous, multiband (similar to 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.
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