A search for variable and transient radio sources in the extended Chandra Deep Field South at 5.5 GHz

Abstract

We present a three epoch survey for transient and variables in the extended Chandra Deep Field South at 5.5 GHz with the Australia Telescope Compact Array. A region covering $\sim$0.3 deg${}^2$ was observed on timescales of 2.5 months and 2.5 years and typical sensitivities 12.1 $-$ 17.1 $\mu$Jy beam${}^{-1}$ (1$\sigma$) were achieved. This survey represents the deepest search for transient and variable radio sources at 5.5 GHz. In total 124 sources were detected above the 5.5$\sigma$ level. One highly variable radio source was found with $\Delta S>50$ implying a surface density of $\sim$3 deg${}^{-2}$. A further three radio sources were found with lower levels of variability equating to a surface density of $\sim$13 deg${}^{-2}$ above a detection threshold of 82.3 $\mu$Jy. All of the variable sources have inverted radio spectra (between 1.4 and 5.5 GHz) and are associated with active galactic nuclei. We conclude that these variables are young gigahertz peaked-spectrum sources with active and self-absorbed radio jets. We explore the variability completeness of this sample and conclude that the fairly low levels of variability would only be detectable in 3$-$25% of all sources within the field. No radio transients were detected in this survey and we place an upper limit on the surface density of transient events $<7.5$ deg${}^{-2}$ above a detection threshold of 68.8~$\mu$Jy.

References in corpus (13)

• 3D-HST WFC3-selected Photometric Catalogs in the Five CANDELS/3D-HST Fields: Photometry, Photometric Redshifts and Stellar Masses
• Science with ASKAP - the Australian Square Kilometre Array Pathfinder
• Science With The Australian Square Kilometre Array Pathfinder
• Deep ATLAS radio observations of the CDFS-SWIRE field
• The properties of extragalactic radio sources selected at 20 GHz
• SubmilliJansky Transients in Archival Radio Observations
• The VLA Survey of the Chandra Deep Field South: I. Overview of the Radio Data
• The variability timescales and brightness temperatures of radio flares from stars to supermassive black holes
• MeerKAT Key Project Science, Specifications, and Proposals
• Calibration update of the COMBO-17 CDFS catalogue
• Variability-selected active galactic nuclei from supernova search in the Chandra deep field south
• Origin of the Counter-Rotating Gas in NGC 1596
• Extragalactic Transients in the Era of Wide-Field Radio Surveys. I. Detection Rates and Light Curve Characteristics

Cited by in corpus (9)

• Fast Radio Bursts
• Quasars That Have Transitioned from Radio-quiet to Radio-loud on Decadal Timescales Revealed by VLASS and FIRST
• Dwarf nova-type cataclysmic variable stars are significant radio emitters
• Radio light curve of the galaxy possibly associated with FRB150418
• Radio-interferometric monitoring of FRB 131104: A coincident AGN flare, but no evidence for a cosmic fireball
• An insight into the extragalactic transient and variable microJy radio sky across multiple decades
• The MASIV Survey IV: relationship between intra-day scintillation and intrinsic variability of radio AGNs
• Optical and radio astrometry of the galaxy associated with FRB150418
• A GMRT 150 MHz Search for Variables and Transients in Stripe 82