2013/03/25 by K. P. Mooley, D. A. Frail, E. O. Ofek +3 · 3 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Chandra Deep Field South #Electromagnetic radiation #Field (mathematics) #Flux (metallurgy) #Galaxies: Formation, Evolution, Phenomena #Gravitational wave #Radio Astronomy Observations and Technology #Sky #Transient (computer programming) #astro-ph.CO #astro-ph.HE
paper · pdf · doi:10.1088/0004-637x/768/2/165
22 pages, 13 figures (25 if individual subfigures are counted), 10 tables. Accepted for publication in The Astrophysical Journal
arxiv created 2013/03/25 · openalex publication_date 2013/04/25 · arxiv updated 2015/06/15 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We report on an analysis of the Extended Chandra Deep Field South (E-CDFS) region using archival data from the Very Large Array, with the goal of studying radio variability and transients at the sub-milliJansky level. The 49 epochs of E-CDFS observations at 1.4 GHz sample timescales from 1 day to 3 months. We find that only a fraction (1%) of unresolved radio sources above 40 μJy are variable at the 4σ level. There is no evidence that the fractional variability changes along with the known transition of radio-source populations below 1 mJy. Optical identifications of the sources show that the variable radio emission is associated with the central regions of an active galactic nucleus or a star-forming galaxy. After a detailed comparison of the efficacy of various source-finding algorithms, we use the best to carry out a transient search. No transients were found. This implies that the areal density of transients with peak flux density greater than 0.21 mJy is less than 0.37 deg −2 (at a confidence level of 95%). This result is approximately an order of magnitude below the transient rate measured at 5 GHz by Bower et al. but it is consistent with more recent upper limits from Frail et al. Our findings suggest that the radio sky at 1.4 GHz is relatively quiet. For multi-wavelength transient searches, such as the electromagnetic counterparts to gravitational waves, this frequency may be optimal for reducing the high background of false positives.