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

Abstract

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 (AGN) 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 Centimeters survey (1993-2011), but they are now consistent with "radio-loud" quasars ($L_{3\mathrm{GHz}}=10^{40-42}\mathrm{erg}{\mathrm{s}}^{-1}$). A quasi-simultaneous, multiband ($\sim 1-18$ GHz) follow-up study of 14 sources with the VLA has revealed compact sources ($<0.1^{\prime \prime }$ 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.

28 pages, 9 figures, accepted to ApJ

References in corpus (41)

• The Supernova -- Gamma-Ray Burst Connection
• A Catalog of Quasar Properties from SDSS DR7
• The Co-Evolution of Galaxies and Supermassive Black Holes: Insights from Surveys of the Contemporary Universe
• The Zwicky Transient Facility: Science Objectives
• The Last of FIRST: The Final Catalog and Source Identifications
• The WISE AGN Catalog
• The Dynamic Evolution of Young Extragalactic Radio Sources
• Accretion states and radio loudness in Active Galactic Nuclei: analogies with X-ray binaries
• Radio Properties of Tidal Disruption Events
• Extragalactic Peaked-Spectrum Radio Sources at Low Frequencies
• Prevalence of radio jets associated with galactic outflows and feedback from quasars
• Radio Loud and Radio Quiet Quasars
• Statistical analyses of long-term variability of AGN at high radio frequencies
• Relativistic jet feedback II: Relationship to gigahertz peak spectrum and compact steep spectrum radio galaxies
• Anticipated Performance of the Square Kilometre Array -- Phase 1 (SKA1)
• Radio Variability in Seyfert Nuclei
• Fundamental differences in the radio properties of red and blue quasars: evolution strongly favoured over orientation
• The variability timescales and brightness temperatures of radio flares from stars to supermassive black holes
• The AGN fuelling/feedback cycle in nearby radio galaxies - I. ALMA observations and early results
• The duty cycle of radio galaxies revealed by LOFAR: remnant and restarted radio source populations in the Lockman Hole
• Asymmetries in Extragalactic Double Radio Sources: Clues from 3D Simulations of Jet - Disc Interaction
• Evolving parsec-scale radio structure in the most distant blazar known
• Nature and evolution of powerful radio galaxies and their link with the quasar luminosity function
• Fundamental differences in the radio properties of red and blue quasars: enhanced compact AGN emission in red quasars
• The Spectral Variability of the GHz-Peaked Spectrum Radio Source PKS 1718-649 and a Comparison of Absorption Models
• Interplanetary Scintillation studies with the Murchison Wide-field Array II: Properties of sub-arcsecond compact sources at low radio frequencies
• Jet-cloud collisions in the jet of the Seyfert galaxy NGC3079
• The flickering nuclear activity of Fornax A
• Jet-driven galaxy-scale gas outflows in the hyper-luminous quasar 3C273
• Interplanetary Scintillation with the Murchison Widefield Array I: A sub-arcsecond Survey over 900 square degrees at 79 and 158 MHz
• Fundamental differences in the radio properties of red and blue quasars: Insight from the LOFAR Two-metre Sky Survey (LoTSS)
• TXS 0128+554: A Young Gamma-Ray Emitting AGN With Episodic Jet Activity
• A search for variable and transient radio sources in the extended Chandra Deep Field South at 5.5 GHz
• High-resolution VLA Imaging of Obscured Quasars: Young Radio Jets Caught in a Dense ISM
• Caltech-NRAO Stripe 82 Survey (CNSS). IV. The Birth of Radio-loud Quasar 013815+00
• Variability and parsec-scale radio structure of candidate compact symmetric objects
• Mid-infrared Variability of gamma-ray emitting blazars
• The curious activity in the nucleus of NGC 4151: jet interaction causing variability?
• Changing-look AGNs or short-lived radio sources?
• Compact Radio Emission from Nearby Galaxies with Mid-infrared Nuclear Outbursts
• GMRT observations of extragalactic radio sources with steeply inverted spectra

Cited by in corpus (9)

• The discovery of a highly accreting, radio-loud quasar at z=6.82
• Accretion-modified Stars in Accretion Disks of Active Galactic Nuclei: Slowly Transient Appearance
• The Quasar Feedback Survey: Discovering hidden Radio-AGN and their connection to the host galaxy ionised gas
• LeMMINGs. III. The e-MERLIN Legacy Survey of the Palomar sample. Exploring the origin of nuclear radio emission in active and inactive galaxies through the [O III] -- radio connection
• Testing the magnetic flux paradigm for AGN radio loudness with a radio intermediate quasar
• A compact core-jet structure in the changing-look Seyfert NGC 2617
• The peculiar WAT NGC 2329 with Seyfert/FR I-like radio lobes
• The Nature of Jets in Double-Peaked Emission Line AGN in the KISSR Sample
• The Unusual Weak-Line Quasar PG1407+265 and its Foreground z~0.7 X-ray Cluster