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GMRTLHCAT - Giant Metrewave Radio Telescope Lockman Hole 610-MHz Radio Source Catalog

HEASARC
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Overview

This table contains a source catalog based on observations of the Lockman Hole with the Giant Metrewave Radio Telescope (GMRT) taken at 610 MHz (49 cm). Twelve pointings were observed, covering a total area of ~5 deg2 with a resolution of 6 x 5 arcsec2, position angle +45 degrees. The majority of the pointings have an rms noise of ~ 60 microJy/beam (uJy/beam) before correction for the attenuation of the GMRT primary beam. The techniques used for data reduction and the production of a mosaicked image of the region are described in the reference paper, where the final mosaic is presented, along with a catalog of 2845 sources detected above the 6-sigma threshold which is contained in this table. In the paper, radio source counts are calculated at 610 MHz and combined with existing 1.4-GHz source counts, in order to show that pure luminosity evolution of the local radio luminosity functions for active galactic nuclei and starburst galaxies is sufficient to account for the two source counts simultaneously.

The 'central region' of the Lockman Hole, consisting of 12 pointings spaced by 36 arcminutes in a hexagonal pattern (shown in Fig. 1 of the reference paper) was observed on 2004 July 24 and 25 using the GMRT. The observations were made in two 16-MHz sidebands centred on 610 MHz, each split into 128 spectral channels, with a 16.9s integration time.


Catalog Bibcode

2008MNRAS.387.1037G

References

A 610-MHz survey of the Lockman Hole with the Giant Metrewave Radio Telescope.
I. Observations, data reduction and source catalogue for the central 5 deg2.
    Garn T., Green D.A., Riley J. M., Alexander P.
   <Mon. Not. R. Astron. Soc. 387, 1037 (2008)>
   =2008MNRAS.387.1037G

Provenance

This table was created by the HEASARC in February 2012 based on CDS Catalog J/MNRAS/387/1037 file catalog.dat.

Parameters

Name
The name of the radio source using the IAU-style designation for the source based on the truncated J2000.0 equatorial coordinates of its centroid, viz., 'GMRTLH JHHMMSS.s+DDMMSS', as registered with the CDS Dictionary of Nomenclature of Celestial Objects, where the GMRTLH prefix stands for 'Giant Metrewave Radio Telescope Lockman Hole'.

RA
The Right Ascension of the source in the selected equinox, calculated using first moments of the relevant pixel brightnesses to give the centroid position. This was given in J2000.0 coordinates to a precision of 0.01 seconds of time in the original table.

Dec
The Declination of the source in the selected equinox, calculated using first moments of the relevant pixel brightnesses to give the centroid position. This was given in J2000.0 coordinates to a precision of 0.1 arcseconds in the original table.

LII
The Galactic Longitude of the radio source centroid.

BII
The Galactic Latitude of the radio source centroid.

Flux_610_MHz
The radio brightness of the peak pixel in the 610-MHz radio source, in mJy/beam.

RMS_610_MHz
The local rms noise near the source position, in mJy/beam (converted by the HEASARC from the uJy/beam units used in the original table).

Int_Flux_610_MHz
The integrated flux density of the 610-MHz radio source, in mJy.

Int_Flux_610_MHz_Error
The error in the integrated flux density of the 610-MHz radio source, in mJy.

Centroid_X_Pixel
The X pixel coordinate from the mosaic image which was closest to the source centroid.

Centroid_Y_Pixel
The Y pixel coordinate from the mosaic image which was closest to the source centroid.

SExtractor_DB_Flag
The SEXTRACTOR (Source Extractor) deblended object flag coded as follows:

     1 = where a nearby bright source may be affecting the calculated flux
     2 = where a source has been deblended into two or more components
         from a single initial 'island' of flux
     3 = when both conditions 1 and 2 apply
  
There are 77 sources present in the catalog with non-zero deblend flags, and it is necessary to examine the GMRT mosaic image, available at http://www.mrao.cam.ac.uk/surveys/GMRT/LH/, to distinguish between the case where one extended object has been represented by 2 or more entries, compared to the case where two astronomically different objects are actually present.

Contact Person

Questions regarding the GMRTLHCAT database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 9-Feb-2012