K. Thorat, R. Subrahmanyan, L. Saripalli, R. D. Ekers
The Australia Telescope Low-brightness survey (ATLBS; \cite{SESS10}) regions
have been mosaic imaged at a radio frequency of 1.4 GHz with $6\arcsec$ angular
resolution and 72 $\mu$Jy beam$^{-1}$ rms noise. The images cover 8.42 square
degrees sky area and have no artifacts or imaging errors above the image
thermal noise and, therefore, form a resource for attempting automated source
identification and classification algorithms. Multi-resolution radio and
optical r-band images were used to recognize multi-component sources and
prepare a source list. 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 to a great
extent by using low resolution (beam FWHM $= 50\arcsec $) radio images, while
effects of source confusion are removed by using high resolution images for
identifying blended sources. The ATLBS counts are systematically lower than
previous estimates. 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.
View original:
http://arxiv.org/abs/1202.0134
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