C. H. Ishwara-Chandra
Articles written in Journal of Astrophysics and Astronomy
Volume 24 Issue 1-2 March 2003 pp 37-43
GMRT detection of HI 21 cm associated absorption towards the
C. H. Ishwara-Chandra K. S. Dwarakanath K. R. Anantharamaiah
We report the GMRT detection of associated HI 21 cm-line absorption in the
Volume 32 Issue 4 December 2011 pp 487-490
The Double–Double Radio Galaxy 3C293
S. A. Joshi S. Nandi D. J. Saikia C. H. Ishwara-Chandra C. Konar
We present the results of radio continuum observations at frequencies ranging from ∼ 150–5000 MHz of the misaligned double–double radio galaxy (DDRG) 3C293 (J1352+3126) using the GMRT and the VLA, and estimate the time-scale of interruption of jet activity to be less than ∼ 0.1 Myr.
Volume 32 Issue 4 December 2011 pp 609-612
High-Redshift Radio Galaxies from Deep Fields
C. H. Ishwara-Chandra S. K. Sirothia Y. Wadadekar S. Pal
Most of the radio galaxies with 𝑧 > 3 have been found using the red-shift spectral index correlation.We have started a programme with the Giant Metrewave Radio Telescope (GMRT) to exploit this correlation at flux density levels about 100 times deeper than the known high-redshift radio galaxies, with an aim to detect candidate high-redshift radio galaxies. Here we present results from the deep 150 MHz observations of LBDS-Lynx field, which has been 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). We find about 150 radio sources with spectra steeper than 1. About two-thirds 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 red-shift.
Volume 32 Issue 4 December 2011 pp 613-614
Deep GMRT 150 MHz Observations of the DEEP2 Fields: Searching for High Red-Shift Radio Galaxies Revisited
Susanta K. Bisoi C. H. Ishwara-Chandra S. K. Sirothia P. Janardhan
High red-shift radio galaxies are best searched at low radio frequencies, due to its steep radio spectra. Here we present preliminary results from our programme to search for high red-shift radio galaxies to ∼ 10 to 100 times fainter than the known population till date. We have extracted ultra-steep spectrum (USS) samples from deep 150 MHz Giant Meter-wave Radio Telescope (GMRT) observations from one of the three well-studied DEEP2 fields to this effect. From correlating these radio sources with respect to the high-frequency catalogues such as VLA, FIRST and NVSS at 1.4 GHz, we find ∼ 100 steep spectrum (spectral index, 𝛼 > 1) radio sources, which are good candidates for high red-shift radio galaxies.
Volume 34 Issue 2 June 2013 pp 141-149
Synergy Between Radio and Optical Telescopes: Optical Followup of Extragalactic Radio Sources
Distance measurement is a must to characterize any source in the sky. In the radio band, it is rarely possible to get distance or redshift measurements. The optical band is the most used band to get distance estimate of sources, even for those originally discovered in other bands of the electromagnetic spectrum. However, the spectroscopic redshift measurements even for fairly bright radio sample is grossly incomplete, implying un-explored discovery space. Here we discuss the scope of optical follow up of radio sources, in particular the radio loud AGNs, from the present generation radio telescopes.
Volume 44, 2023
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