Deep GMRT 150 MHz observations of LBDS

C. H. Ishwara-Chandra, S. K. Sirothia, Y. Wadadekar, S. Pal, Rogier Windhorst

Research output: Contribution to journalConference articlepeer-review


The most efficient way to search for high redshift radio galaxies is to use its steep radio spectra as high-redshift indicator. Most of the radio galaxies with z > 3 have been found using this redshift-spectral index correlation. We have started a programme with the Giant Metrewave Radio Telescope (GMRT) to exploit this correlation at flux density levels about 10 to 100 times deeper than the known high-redshift radio galaxies which were identified primarily using the already available radio catalogues. In our programme, we have obtained deep, high resolution radio observations at 150 MHz with GMRT for severaldeep fields which are well studied at higher radio frequencies and in other bands of the electromagnetic spectrum, with an aim to detect candidate high redshift radio galaxies. In this poster we present results from the deep 150 MHz observations of LBDS-Lynx field, which has been already imaged at 327, 610 and 1412 MHz with the Westerbork Synthesis Radio Telescope (WSRT) and at 1400 and 4860 MHz with the Very Large Array (VLA). The 150 MHz image made with GMRT has a rms noise of ∼ 0.7 mJy/beam and a resolution of ∼ 19′′ × 15′′. It is the deepest low frequency image of the LBDS-Lynx field. The source catalog of this field at 150 MHz has about 765 sources down to ∼ 20% of the primary beam response, covering an area of about 15 degree2. Spectral index was estimated by cross correlating each source detected at 150 MHz with the available observations at 327, 610, 1400 and 4860 MHz and also using available radio surveys such as WENSS at 327 MHz and NVSS and FIRST at 1400 MHz. We find about 150 radio sources with spectra steeper than 1. About two-third of these are not detected in Sloan Digital Sky Survey (SDSS), hence are strong candidate high-redshift radio galaxies, which need to be further explored with deep infra-red imaging and spectroscopy to estimate the redshift.

Original languageEnglish (US)
Article number069
JournalProceedings of Science
StatePublished - 2010
Event2010 ISKAF Science Meeting, ISKAF 2010 - Assen, Netherlands
Duration: Jun 10 2010Jun 14 2010

ASJC Scopus subject areas

  • General


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