Abstract Details

Name: Manami Roy
Affiliation: Raman Research Institute
Conference ID: ASI2020_213
Title : Circumgalactic medium of Milky Way : Clues from highly ionizaed oxygen lines
Authors and Co-Authors : Manami Roy, Biman B. Nath
Abstract Type : Poster
Abstract Category : Stars, ISM and Galaxy
Abstract : Circumgalactic medium (CGM) is a region surrounding the optically visible part of the galaxy and extending up to the virial radius and perhaps even beyond. It has been inferred that a large amount of the baryons resides in this diffuse gaseous reservoir. CGM has an important role in star formation and galaxy evolution: it plays the role of the galactic fuel tank, waste dump, and recycling center for the galactic flows, all at the same time. The study of CGM is therefore important to understand galactic evolution. Its temperature and density profiles are still uncertain but the presence of different ionization lines in the absorption spectra through CGM points towards multi-phase temperature and density structure. We have studied the CGM in the light of observed column densities of highly ionized oxygen lines. As a template, we considered a physically motivated density and temperature structure of CGM in hydrostatic equilibrium in the 'precipitation model' where t_cool/t_ff=10. In addition, we considered the effect of log-normal temperature distribution around the mean at every radius, reflecting the presence of multiphase gas, and the effects of both collisional ionization and photoionization by the extra-galactic radiation field. Star-forming galaxies also show the signature of multi-phase gas in their CGM. We find that the observed N(OVII)/N(OVIII) can be explained in this model without resorting to a single-zoned model as has been done previously. We also find that the predicted N(OVII) and N(OVIII) values as a function of galactic latitude and longitude agree well with observations excluding the regions of Fermi-bubbles and local bubble.