J/ApJ/762/16 Australia Telescope Low-brightness Survey (ATLBS) (Thorat+, 2013)
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)>
=2013ApJ...762...16T 2013ApJ...762...16T
ADC_Keywords: Radio sources ; Surveys
Keywords: catalogs; methods: data analysis; radio continuum: galaxies; surveys
Abstract:
The Australia Telescope Low-brightness Survey (ATLBS) regions have
been mosaic imaged at a radio frequency of 1.4GHz with 6" angular
resolution and 72µJy/beam rms noise. The images (centered at
RAJ2000=00:35:00, DEJ2000=-67:00:00 and RAJ2000=00:59:17,
DEJ2000=-67:00:00) cover 8.42deg2 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 4m CTIO Blanco telescope)
were used to recognize multi-component sources and prepare a source
list; the detection threshold was 0.38mJy in a low-resolution radio
image made with beam FWHM of 50". Radio source counts in the flux
density range 0.4-8.7mJy 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 1mJy the ATLBS counts
are systematically lower than the previous estimates. Showing no
evidence for an upturn down to 0.4mJy, 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:
The radio observations that form the Australia Telescope
Low-brightness Survey (ATLBS) survey were made with the different
array configurations of the ATCA. The observations were made in the
20cm band, with a center frequency of 1388MHz. These observations
recorded visibilities in full polarization mode.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 48 1366 The Australia Telescope Low-brightness Survey
(ATLBS) survey 1.4GHz source catalog
--------------------------------------------------------------------------------
See also:
VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)
J/ApJS/203/15 : Counterparts to 1.4GHz sources in ECDF-S (Bonzini+, 2012)
J/ApJS/199/27 : The ATLBS Extended Source Sample (Saripalli+, 2012)
J/MNRAS/402/2792 : 1388MHz ATLBS Low-Brightness Survey (Subrahmanyan+, 2010)
J/AJ/135/2470 : Radio observations of the HDFS region. IV. (Huynh+, 2008)
J/AJ/130/1373 : Radio observations of the HDFS region. II (Huynh+, 2005)
J/AJ/125/465 : Phoenix Deep Survey 1.4-GHz microJy Catalog (Hopkins+, 2003)
J/ApJ/533/611 : 1.4GHz survey in HDF region (Richards+, 2000)
J/A+AS/58/1 : 1412 MHz catalogue of Westerbork survey. I. (Windhorst+, 1984)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 13 A13 --- ATLBS Source name (JHHMM.m+DDMMa) (1)
15- 16 I2 h RAh [0/1] Hour of Right Ascension (J2000)
18- 19 I2 min RAm Minute of Right Ascension (J2000)
21- 25 F5.2 s RAs Second of Right Ascension (J2000)
27 A1 --- DE- [-] Sign of the Declination (J2000)
28- 29 I2 deg DEd [65/68] Degree of Declination (J2000)
31- 32 I2 arcmin DEm Arcminute of Declination (J2000)
34- 37 F4.1 arcsec DEs Arcsecond of Declination (J2000)
39- 44 F6.2 mJy Sint [0.3/290] Integrated flux density at 1.4GHz
46 A1 --- Type Source type based on high resolution image (2)
48 I1 --- N [1/4]? Number of components for complex sources
--------------------------------------------------------------------------------
Note (1): Based on the centroid of the radio emission.
Note (2): Source type as follows:
C = a "complex" source;
G = a single component Gaussian;
P = an unresolved source;
M = a source undetected in the high resolution image.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 28-Aug-2014