Abstract Details
| Name: Gargi Shaw Affiliation: Centre for excellence in basic sciences, Mumbai Conference ID: ASI2015_508 Title : Effect of metallicity and cosmic ray ionization rate on the 21 cm spin temperature. Authors and Co-Authors : Gary Ferland University of Kentucky, USA Abstract Type : Oral Abstract Category : Extragalactic astronomy Abstract : Most of our knowledge about the distribution of neutral atomic hydrogen in the ISM of the Milky Way and other galaxies comes from 21 cm observations which originates from the transition between the hyperfine levels within the 1S term of H0. If the level populations are collisionally dominated in the absence of other non-thermal processes, the 21 cm line will trace the kinetic temperature. However, the level populations can be affected by non-thermal radiative processes. Here we present a number of numerical simulations of environments, using the spectral simulation code Cloudy, varying the metallicity and cosmic-ray ionization rate with a detailed treatment of the physical processes that determine level populations within H0. This includes detailed Lyman line transfer and the effects of cosmic-ray excitation and continuum pumping. Our simulations show that the 21cm spin temperature is certainly dependent on the metallicity and the cosmic ray ionization rate. |