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| Paper: |
Results from GMRT 150 MHz Radio Observations: Search for Steep Spectrum Radio Sources |
| Volume: |
380, At the Edge of the Universe: Latest Results from the Deepest Astronomical Surveys |
| Page: |
237 |
| Authors: |
Ishwara-Chandra, C.H.; Marathe, R. |
| Abstract: |
We present results from deep 150 MHz low frequency radio observations with Giant Meterwave Radio Telescope (GMRT), India. GMRT consists of 30 antennas, each of 45 meter diameter operating at frequencies from 150 MHz to 1400 MHz. At 150 MHz, GMRT can image the sky with high resolution (~ 20″) of area of ~ 10 square degrees with single pointing, which allows to detect a few hundred radio sources down to ~ 10 mJy. We have carried out deep imaging at 150 MHz of two fields; one surrounding Upsilon Andromeda and another encompassing the cluster Abell 764. The rms noise achieved is ~ 2 mJy/beam. The resolution in both images were ~ 20″. The radio spectral index analysis of the sources in the field using the higher frequency NVSS (1400 MHz) flux densities with GMRT flux densities at 150 MHz helps us to detect sources with extreme spectral indices. Because the majority of high redshift radio sources tend to exhibit steeper radio spectra, deep imaging of the fields with GMRT at 150 MHz will help to detect/discover high redshift radio sources. Our analysis shows that ~ 8% of the sources detected at 150 MHz have very steep spectra with the spectral index exceeding 1.25 (Sv ∝ v−α). |
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