Inferences from imaging extended radio sources in deep radio surveys

K. Thorat1,2*, R. Subrahmanyan1, L. Saripalli1 and R. D. Ekers3,1
1Raman Research Institute, C. V. Raman Avenue, Sadashivanagar, Bangalore 560080, India
2Joint Astronomy Programme, Indian Institute of Science, Bangalore 560012, India
3CSIRO Astronomy and Space Sciences, Epping, NSW 2121, Australia

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From the scales of the cosmic web to sub-kpc scales in ‘radioquiet’ Seyfert galaxies, di use radio emission may form a component critical to our understanding of physics of extragalactic objects. Di erent aspects of the latter, ranging from the life-cycles of radio galaxies and the nature and cosmic evolution of sub-mJy radio population to dynamics of clusters of galaxies involve imaging di use radio emission. The observational diculties imaging such di use emission which may typically be seen at low surface brightness levels makes sensitive radio surveys a necessity. Australia Telescope Low Brightness Survey(ATLBS) is such a survey. A radio survey at 1.4 GHz, it images 8.4 square degrees in the southern sky. Herein the results of studies of the radio sources in ATLBS survey are presented. We first demonstrate the importance of multi-resolution radio images and automated algorithms in accurately estimating the counts of radio sources in the submilliJansky flux density range. Using unique detection strategies to simultaneously mitigate e ects of confusion and resolution bias, we have examined the counts of sources in the submilliJansky flux range. Using source counts as opposed to component counts, we find substantially lower counts below 1 mJy and conclude that the dominance of new populations is at lower flux densities than previously reported. Finally, we present a sample of radio sources chosen from the ATLBS survey regions and examine the links between the radio morphologies and their large scale optical environments using a novel method.

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