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Title: High-resolution imaging of the ATLBS regions:The radio source counts
Authors: Thorat, K.
Subrahmanyan, Ravi
Saripalli, Lakshmi
Ekers, R.D.
Keywords: catalogs methods
data analysis radio continuum
galaxies surveys
Issue Date: Jan-2013
Publisher: IOP Publishing for the American Astronomical Society
Citation: The Astrophysical Journal , 2013, Vol,762, p16
Abstract: The Australia Telescope Low-brightness Survey (ATLBS) regions have been mosaic imaged at a radio frequency of 1.4 GHz with 6'' angular resolution and 72 μJy beam-1 rms noise. The images (centered at R.A. 00h35m00s, decl. -67°00'00'' and R.A. 00h59m17s, decl. -67°00'00'', J2000 epoch) cover 8.42 deg2 sky area and have no artifacts or imaging errors above the image thermal noise. Multi-resolution radio and optical r-band images (made using the 4 m CTIO Blanco telescope) were used to recognize multi-component sources and prepare a source list; the detection threshold was 0.38 mJy in a low-resolution radio image made with beam FWHM of 50''. Radio source counts in the flux density range 0.4-8.7 mJy are estimated, with corrections applied for noise bias, effective area correction, and resolution bias. The resolution bias is mitigated using low-resolution radio images, while effects of source confusion are removed by using high-resolution images for identifying blended sources. Below 1 mJy the ATLBS counts are systematically lower than the previous estimates. Showing no evidence for an upturn down to 0.4 mJy, they do not require any changes in the radio source population down to the limit of the survey. The work suggests that automated image analysis for counts may be dependent on the ability of the imaging to reproduce connecting emission with low surface brightness and on the ability of the algorithm to recognize sources, which may require that source finding algorithms effectively work with multi-resolution and multi-wavelength data. The work underscores the importance of using source lists—as opposed to component lists—and correcting for the noise bias in order to precisely estimate counts close to the image noise and determine the upturn at sub-mJy flux density.
Description: Restricted Access. An open-access version is available at Articles older than 2 years are open to all at the journal site
ISSN: 0004-637X
1538-4357 (Online)
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Copyright: 2013 The American Astronomical Society
Appears in Collections:Research Papers (A&A)

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