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GMRT Lockman Hole

The 610-MHz GMRT surveys of the Lockman Hole

Two surveys of the Lockman Hole made with the GMRT at 610 MHz have been published:

  1. A survey of the inner ~5 square degrees of Lockman Hole region, published in 2008;
  2. A shallower survey of an additional ~8 square degrees of Lockman Hole region, published in 2010 (in press).

(1) Inner survey

This survey is the third in a series of surveys of the deep Spitzer legacy fields, taken at 610 MHz with the Giant Metrewave Radio Telescope (GMRT). Full details of the observations, data reduction, mosaic and source catalogue can be found in Garn T., Green D. A., Riley J. M., Alexander P. (2008, MNRAS, 387, 1037) (or arXiv:0804.2421 [arXiv]).

Summary

We present observations of a central portion of the Lockman Hole, taken at 610 MHz with the Giant Metrewave Radio Telescope (GMRT). Twelve pointings were observed, covering a total area of ~5 square degrees with a resolution of 6″ × 5″, position angle +45°. The majority of the pointings have an rms noise of ~60 μJy before primary beam correction. Techniques used for the data reduction and production of a mosaicked image of the region are described, and the final mosaic is presented, along with a catalogue of 2845 sources detected above 6 σ. 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 mosaicked image and source catalogue are available through links in the table below.

FITS ImageASCII catalogueCDS-style ReadMe for catalogue
GMRT_LH_dr1.fits GMRT_LH_dr1.dat ReadMe

Two modifications were made to the UV data before image processing – both using custom-made AIPS tasks. The tasks, along with full descriptions, are available via the links below:

  • UVFLP reorders the uv channels so that the upper and lower sidebands can be combined together, increasing the uv coverage for the image.
  • UVFXT corrects the time-stamps on GMRT data for an error in the online software at the GMRT (now fixed).

(2) Outer survey

This survey is one in a series of surveys of the deep Spitzer legacy fields, taken at 610 MHz with the Giant Metrewave Radio Telescope (GMRT). Full details of the observations, data reduction, mosaic and source catalogue can be found in Garn T., Green D. A., Riley J. M., Alexander P. (2010, BASI, 38, 103) (or arXiv:1008.2777 [arXiv]).

Summary

We present observations of the Lockman Hole, taken at 610 MHz with the Giant Metrewave Radio Telescope (GMRT). An earlier survey (Garn et al. 2008, MNRAS, 387, 1037) had 12 pointings covering ~5 square degrees in the centre of the Lockman Hole, and here a further 26 pointings in the outer parts of the Lockman Hole are added, to cover a total of ~14 square degrees. To match the earlier survey, images were made with a resolution of 6″ × 5″, position angle +45°. The majority of the pointings have an rms noise of ~80 μJy before primary beam correction, but the noise in the west — particularly near the very bright source 3C244.1 — is worse.

The mosaicked image and a catalogue of 4934 sources are available through links in the table below.

FITS ImageASCII catalogueCDS-style ReadMe for catalogue
GMRT_LH2_dr1.fits GMRT_LH2_dr1.dat ReadMe

Last modified 15 August 2010

Dave Green (D.A.Green@mrao.cam.ac.uk)