C. H. Ishwara Chandra

Search for high-redshift radio galaxies using observations with the GMRT:

Despite several decades of efforts, only one radio galaxy is known at redshift > 5 (discovered in 1999), though there are close to 50 high-redshift radio galaxies (HzRGs) with z > 3. Nearly all of them have been found using the redshift-spectral index correlation. We have started a program with the Giant Metrewave Radio Telescope (GMRT) to exploit this correlation at flux density levels of about 10 to 100 times deeper than the known HzRGs. In this program, we have obtained deep, high-resolution radio observations at 150 MHz with GMRT for several DEEP 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. From the deep 150 MHz observations of the LBDS-Lynx field, along with available auxiliary data, we have found about 150 radio sources with spectra steeper than 1. About two-third of these are not detected in Sloan Digital Sky Survey and are hence strong candidates for high-redshift radio galaxies. These need to be further explored with deep infra-red imaging and optical spectroscopy to get the redshift. Work on other deep fields is now in progress.


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