ﻻ يوجد ملخص باللغة العربية
We present radio observations of ultraluminous infrared galaxies (ULIRGs) using the Giant Metrewave Radio Telescope (GMRT) and combine them with archival multi-frequency observations to understand whether ULIRGs are the progenitors of the powerful radio loud galaxies in the local Universe. ULIRGs are characterized by large infrared luminosities ($L_{IR}>$10$^{12}$L$odot$), large dust masses ($sim10^{8}M_{odot}$) and vigorous star formation (star formation rates $sim$10-100 $M_{odot}~$yr$^{-1}$). Studies show that they represent the end stages of mergers of gas-rich spiral galaxies. Their luminosity can be due to both starburst activity and active galactic nuclei (AGN). We study a sample of 13 ULIRGs that have optically identified AGN characteristics with 1.28~GHz GMRT observations. Our aim is to resolve any core-jet structures or nuclear extensions and hence examine whether the ULIRGs are evolving into radio loud ellipticals. Our deep, low frequency observations show marginal extension for only one source. However, the integrated radio spectra of 9 ULIRGs show characteristics that are similar to that of GPS/CSS/CSO/young radio sources. The estimated spectral ages are 0.4 to 20 Myr and indicate that they are young radio sources and possible progenitors of radio galaxies. Hence, we conclude that although most ULIRGs do not show kpc scale extended radio emission associated with nuclear activity, their radio spectral energy distributions do show signatures of young radio galaxies.
We have observed seven nearby large angular sized galaxies at 0.33 GHz using GMRT with angular resolution of $sim10$ and sub-mJy sensitivity. Using archival higher frequency data at 1.4 or $sim$6 GHz, we have then determined their spatially resolved
In order to understand the possible mechanisms of recurrent jet activity in radio galaxies and quasars, which are still unclear, we have identified such sources with a large range of linear sizes (220 $-$ 917 kpc), and hence time scales of episodic a
Using the Alternative Data Release of the TIFR GMRT Sky Survey (TGSS), we studied the low-frequency properties of FR0 radio galaxies, the large population of compact radio sources associated with red massive early-type galaxies revealed by surveys at
We present X-ray and multi-frequency radio observations of the central radio sources in several X-ray cavity systems. We show that targeted radio observations are key to determining if the lobes are being actively fed by the central AGN. Low frequenc
We present the first high-resolution 230-470 MHz map of the Perseus cluster obtained with the Karl G. Jansky Very Large Array. The high dynamic range and resolution achieved has allowed the identification of previously-unknown structures in this near