Author(s): J.M. Norris, Astronomy & Astrophysics, The Pennsylvania State University, University Park, Pennsylvania, UNITED STATES|
Institution(s): 1. Astronomy & Astrophysics, The Pennsylvania State University, University Park, PA, United States.
Contributing team(s): (none)
To understand the formation and evolution of galaxies, it is essential to understand the gas that exists in the vicinity of galaxies. Mg+ absorption systems probe the circumgalactic medium (CGM) around galaxies and can provide hints to the nature of the gas around galaxies. To fully understand the complex structure of the CGM, it is necessary to investigate not only low-ionization transitions such as those of Mg+, but also transition lines associated with more diffuse high-ionization material usually observed in the UV. We report our analysis of eight intervening quasar absorption line systems, which probe the CGM at redshifts 0.4 < z < 1.0. We model these systems as multi-phase material and constrain the parameters of our model by fitting to many ionization transitions including those of Mg+, C3+, O5+, Fe+, Ne7+, N4+, Mg0, O3+, S4+, Si+, Si3+, C+, C2+, N+, N2+, and the H Lyman series. The talk will feature a system at redshift z = 0.48 with a multi-phase structure that includes both gas with metallicity [Fe/H] < -2.5 as well as low- and high-ionization gas with metallicity near solar. We will also discuss a low-ionization system with detected molecular H2 that also has significant O5+ detected at nearly the same velocity. The physical properties of several other systems will be discussed , with a focus on new HST/COS coverage of high-ionization transition lines.