Abstract Details
| Name: Katherine Rawlins Affiliation: UM-DAE Centre for Excellence in Basic Sciences, Mumbai Conference ID: ASI2016_473 Title : Multi-component $H_{2}$ absorption in a damped Lyman-$\alpha$ absorber at $z_{abs}$ = 2.054 - spectroscopic analysis & simulation Authors and Co-Authors : Gargi Shaw (UM-DAE Centre for Excellence in Basic Sciences, University of Mumbai, Santa Cruz East, Mumbai 400 098, India), Raghunathan Srianand (Inter-University Centre for Astronomy & Astrophysics, Post Bag 4, Ganeshkhind, Pune University Campus, Pune 411 007, India), Hadi Rahmani (Aix Marseille Universite, CNRS, Laboratoire d’Astrophysique de Marseille UMR 7326, 13388, Marseille, France) & Rajeshwari Dutta (Inter-University Centre for Astronomy & Astrophysics, Post Bag 4, Ganeshkhind, Pune University Campus, Pune 411 007, India) Abstract Type : Oral Abstract Category : Extragalactic astronomy Abstract : Damped Lyman-$\alpha$ absorbers (DLAs) are quasar absorption line systems with very high column densities of neutral hydrogen, N(H I) ≥ $10^{20.3}$ $cm^{-2}$. They are inter-galactic clouds associated with star formation and are important to our understanding of galaxy formation and evolution. However, despite the large values of N(H I), $H_{2}$ is detected in only 10-15% of all DLAs. We perform detailed spectroscopic analysis & simulation of an $H_{2}$-bearing DLA at $z_{abs}$ = 2.054 towards the quasar J2340-0053. This system is spread over 14 components. Out of these, 7 components show $H_{2}$ absorption. Such multi-component molecular absorption features are rare, making this an interesting system to study. The spectrum was obtained using the Ultraviolet & Visual Echelle Spectrograph at the Very Large Telescope, Chile. We derive column densities for the various observed species - Al III, C II*, Al II, Si II, S II, Fe II, Ni II, Zn II, C I, Mg I and $H_{2}$ - using the Voigt profile fitting package VPFIT (http://www.ast.cam.ac.uk/~rfc/vpfit.html). $H_{2}$ is detected in the lowest six rotational levels of the ground vibrational state. We get a rough estimate of metallicity, dust-to-gas ratio, and the possible range of gas temperature and hydrogen density from the observed column densities. The spectral synthesis code CLOUDY (http://www.nublado.org/) is then used to simulate the prevailing physical conditions in the $H_{2}$ components individually. These well-constrained models for the $H_{2}$ components help us to deduce the physical structure of this DLA cloud accurately. |