C. H. Ishwara Chandra

Professor H
Email: ishwar [at] ncra.tifr.res.in
Phone: +91 - 20 - 25719228
Extn: 9228
Office: F227
National Centre for Radio Astrophysics
Tata Institute of Fundamental Research
Savitribai Phule Pune University Campus,
Pune 411 007
Maharashtra, INDIA

Main Research Areas: Radio Galaxies and Quasars, TIFR-GMRT-Sky Survey.



After finishing his M.Sc. (Physics) from Calicut University, Kerala, in 1992, Ishwara Chandra joined the Joint Astronomy Programme (JAP) run by the Indian Institute of Science, Bangalore, for his Ph.D in the same year. In 1993, he moved to NCRA, Pune, under JAP, for his Ph.D. studies on Unification Scheme for Radio Galaxies and Quasars. He finished his Ph.D. in 1999. He then worked as a post-doctoral fellow at the Raman Research Institute, Bangalore, and later the ISRO Satellite Centre, Bangalore. He joined the National Centre for Radio Astrophysics as a faculty member in June 2002.

Research description:

Radio Galaxies and Quasars:
Powerful radio sources reside in massive galaxies, and finding radio galaxies at earlier cosmological epochs is important to understand the evolution of galaxies. Host galaxies of high redshift radio sources show very high star formation rates and also large reservoirs of dust and gas. These are believed to be the precursors of massive elliptical galaxies in the local Universe. Low frequency radio spectra provide the most efficient method to find these high redshift radio galaxies (HzRGs). We have been using the low frequency data from GMRT, particularly at 150 MHz, to search for steep spectrum radio sources which are good candidates for these HzRGs. We have conclusively shown that known HzRGs represent the tip of the ice-berg; "normal population" of HzRGs, which are yet to be discovered, are well within the reach of current generation instruments like GMRT. From one of the deep fields, we produced a list of about 100 strong candidates for HzRGs. These candidates will be followed up with large optical telescopes in the coming years. We are also re-observing several of these fields at 325 MHz. Such deep radio surveys have long lasting value; they can be used to study evolution of radio sources from highest luminosity to faintest end of star-burst galaxies.
TIFR-GMRT-Sky Survey:
The TIFR GMRT Sky Survey (TGSS) is an all sky survey, covering an area of about 90% of the sky, from declination of -55 degree to +90 degree, at 150 MHz using the GMRT (http://tgss.ncra.tifr.res.in) This survey is expected to fulfill a prominent goal of the GMRT and will prove to be a major database for multi-wavelength astronomy. TGSS will yield a large number of high-redshift radio galaxy candidates, which will be systematically followed up with optical telescopes. I am also interested in searching for new giant radio sources, double-double radio sources and relic radio sources in the TGSS.

Selected publications:

1. Deep GMRT radio observations and a multi-wavelength study of the region around HESS J1858+020 (Paredes, J. M., Ishwara-Chandra, C.H. et al. 2013, A&A (in press), arxiv:1312.3752)

2. Synergy Between Radio and Optical Telescopes: Optical Followup of Extragalactic Radio Sources ( Ishwara-Chandra, C.H. 2013, JAA, 34, 141)

3. Low-frequency radio observations of Seyfert galaxies: A test of the unification scheme. (Singh, V., Shastri, P., Ishwara-Chandra, C. H. & Athreya, R. 2013, A&A, 554, 85)

4. Deep GMRT 150-MHz observations of the LBDS-Lynx region: ultrasteep spectrum radio sources (Ishwara-Chandra, C. H. et al. 2010, MNRAS, 405, 436)

5. A radio study of the double-double radio galaxy 3C293 (Joshi, S. A., Nandi, S., Saikia, D. J., Ishwara-Chandra, C. H., Konar, C. 2011, MNRAS, 414, 1397)

6. Deep low-frequency observations with the Giant Metrewave Radio Telescope: a search for relic radio emission (Sirothia, S. K., Saikia, D. J., Ishwara-Chandra, C. H., Kantharia, N. G. 2009, MNRAS, 392, 1403)

7. Radio detections towards unidentified variable EGRET sources (Paredes, J. M., Marti, J., Ishwara-Chandra C. H. et al. 2008, A&A, 482, 247)

8. Low-frequency radio monitoring of microquasars (Pandey, M., Rao, A. P., Ishwara-Chandra, C. H. et al. 2007, A&A, 463, 567)

9. Radio, millimeter and optical monitoring of GRB 030329 afterglow: constraining the double jet mode (Resmi, L., Ishwara-Chandra, C. H. et al. 2005, A&A, 440, 477)

10. GMRT Detection of HI 21 cm Associated Absorption towards the z=1.2 Red Quasar 3C190 (Ishwara-Chandra, C. H. et al. 2003, JApA, 24, 37)