The Australia Telescope Low-brightness Survey (ATLBS) regions have been
mosaic imaged at a radio frequency of 1.4 GHz with 6 arcseconds angular
resolution and 72 microJansky per beam (uJy/beam) rms noise. The images
(centered at RA 00h 35m 00s, Dec -67o 00' 00" and RA 00h 59m
17s, Dec -67o 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 of 1366 1.4-GHZ sources; the detection threshold was 0.38 mJy
in a low-resolution radio image made with beam FWHM of 50 arcseconds. 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
High-resolution Imaging of the ATLBS Regions: The Radio Source Counts
Thorat K., Subrahmanyan R., Saripalli L., Ekers R.D.
<Astrophys. J. 762, 16 (2013)>
This table was created by the HEASARC in April 2013 based on an
electronic version of Table 2 from the reference paper that was obtained from
the ApJ web site..
The source designation as given in the reference paper using the
prefix 'ATLBS' for 'Australia Telescope Low-Brightness Survey' together with
the J2000.0 equatorial coordinates of the source centroid, e.g.,
The Right Ascension of the centroid of the radio emission in the
selected equinox. This was given J2000.0 coordinates to a precision of 0.01
seconds of time in the original table.
The Declination of the centroid of the radio emission in the
selected equinox. This was given J2000.0 coordinates to a precision of 0.1
arcseconds in the original table.
The Galactic Longitude of the centroid of the radio emission.
The Galactic Latitude of the centroid of the radio emission.
The integrated 1.4-GHz flux density of the radio source, in
The 1.4-GHz source type based on the high-resolution image:
C = a `complex' source;
G = a single component Gaussian;
P = an unresolved source;
M = a source undetected in the high-resolution image.
The number of components in the source: this is given only for complex
Questions regarding the ATLBS1P4GH database table can be addressed to the
HEASARC User Hotline.
Page Author: Browse Software Development Team
Last Modified: 1-Apr-2013