Abstract Details
| Name: Aditya J N H S Affiliation: NCRA Conference ID: ASI2015_480 Title : Cold gas in flat spectrum sources at high redshifts Authors and Co-Authors : Nissim kanekar (Phd supervisor) Abstract Type : Poster Abstract Category : Extragalactic astronomy Abstract : Searches for HI-21cm absorption at the redshift of active galactic nuclei (AGNs) enable detailed studies of the kinematics and distribution of the neutral gas close to the AGN, important for understanding the physics of the AGN activity (which may be fuelled and perhaps even triggered by the neutral gas). Detections of associated absorptions may lead to determine possible variations in the inflow and outflow characteristcs with redshift, depending upon the absorption features which are redshifted or blueshifted from the systemic velocity. Also, detections of outflows of cold gas will establish the presence of feedack mechanism, operating in such systems, though determination of the exact mechanism, viz: AGN induced feedback or Stellar outbursts, may be done with the help of VLBI studies. Such associated HI-21cm absorption studies also allow direct tests of unification schemes for radio galaxies and quasars, which predict that the line of sight to broad-line radio galaxies is normal to the torus and the thick disk, while that towards narrow-line radio galaxies lies close to the plane of the disk. Searches for such absorbers over a wide redshift range will give insight into the possible evolution of AGN environments with redshift. Unfortunately, such associated HI-21cm absorption studies have mostly been carried out at relatively low redshifts, with only four detections at z>1. We are currently using the GMRT to probe AGN environments at high redshifts, out to z~3.6, by searching for associated HI-21cm absorption in a large flat-spectrum AGN sample. |