Dwarakanath, K S

e-mail: dwaraka@rri.res.in

(1978- )

His research interests have been in the following areas:

Low-frequency Sky
He and his colleagues have made an image of the sky at low radio frequencies ($\sim$ 30 MHz). By using a novel technique, the entire observable sky was imaged in one-day. This image gives the details of the sky at an angular resolution comparable to the angular size of the moon. Another unique feature of this image is that it gives the absolute brightness temperature of the sky. Several studies related to the radio emission from the Galactic non-thermal background, supernova remnants, ionised Hydrogen regions, globular clusters, and galaxy clusters were carried out using this image. Some aspects of the evolution of supernova remnants were also carried out.

Diffuse matter in the Galaxy
He and his colleagues have addressed issues concerning the cold and warm atomic hydrogen gas in the Galaxy. The spin temperature of the warm gas in the Galaxy was estimated using 21 cm line absorption experiments. In the context of the cold atomic gas, the nature of the gas seen in optical absorption lines is being studied through the 21 cm line absorption experiments. Small angular scale structure in the cold atomic gas is being studied using high angular resolution images of the Galaxy in 21 cm line absorption.

Diffuse matter in Galaxy Clusters
Observations of the 21 cm line absorption to detect the cold gas in the cores of clusters were carried out. This led to interesting constraints on the amount of hot gas cooling in the cores of galaxy clusters. In addition, 21 cm line emission studies were carried out to estimate the gas content of galaxies in clusters. A comparison of the mass of these galaxies with the corresponding ones outside the clusters has shown the effect of environment on the galaxies. Radio continuum emission from cluster galaxies, along with optical spectroscopy was used to study the population of radio sources in clusters. The population differences between different clusters indicate environmental effects. A long-term program is to study how the gas content and the star formation rate in cluster galaxies change with redshift.

Selected Publications:

1. K. S. Dwarakanath, R. K. Shevgaonkar, Ch. V. Sastry; Observations of the supernova remnants HB9 and IC443 at 34.5 MHz, J. Astrophys. Astr., 3, 207, (1982).

2. G. Srinivasan, K. S. Dwarakanath; A new look at the birthrate of supernova remnants, J. Astrophys. Astr., 3, 351, (1982).

3. G. Srinivasan, D. Bhattacharya, K. S. Dwarakanath; On the supernova remnants produced by pulsars, J. Astrophys. Astr., 5, 403, (1984).

4. K. S. Dwarakanath, & N. Udaya Shankar; A synthesis map of the sky at 34.5 MHz, J. Astrophys. Astr., 11, 323, (1990).

5. K. S. Dwarakanath; Low-frequency observations of the Vela supernova remnant and their implications, J. Astrophys. Astr., 12, 199, (1991).

6. K. S. Dwarakanath, J. H. van Gorkom, F. N. Owen; A VLA search for neutral Hydrogen in cooling flow clusters, Astrophys. J., 432, 469, (1994).

7. C. L. Carilli, K. S. Dwarakanath, W. M. Goss; Detection of HI 21 cm absorption by the warm neutral medium, Astrophys. J., 502, L79, (1998).

8. K. S. Dwarakanath, F. N. Owen; On the different radio source populations in the Butcher-Oemler clusters A2125 & A2645, Astronomical J., 118, 625, (1999).