Date of Award
Open Access Dissertation
Physics and Astronomy
Varsha P. Kulkarni
Absorption spectroscopy of gravitationally lensed quasars (GLQs) enables study of spatial variations in the interstellar and/or circumgalactic medium (ISM, CGM) of foreground galaxies. In this work I present observations of 4 GLQs, each with two images separated by 0.8-3.000, that show strong absorbers at redshifts 0.4 abs< 1.3 in their spectra, including some at the lens redshift. The H I Lyman lines were measured in five absorbers using HST-STIS, and metal lines with either the MagE spectrograph or the Sloan Digital Sky Survey. These data, combined with the literature, show no strong correlation between absolute values of differences in NH I, NFe II, or [Fe/H] and sight line separations at absorber redshifts. The measured abundance gradients show a tentative anti-correlation with abundances at galaxy centers.
A study of the lens galaxy foreground to the doubly lensed quasar SBS 0909+532 reveals a large difference in H I and metal column densities between sight lines. Using archival HST-STIS and Keck HIRES spectra, log N H I 18.18 cm−2 and log N H I = 20.38±0.02 cm−2were measured, resulting in a 99% fractional difference in log NH I between sight lines, the highest for a lens galaxy in which H I has been measured. Supersolar values of NFe II/NMg II for all but one component in the HIRES spectra suggests that Type Ia supernovae made a contribution to the chemical enrichment of the lens.
Additionally this work addresses how sensitively measurements of element abundances from astrophysical spectroscopy depend on the atomic data used. We created a compilation of the latest atomic data for resonant absorption lines at wavelengths longward of 911.753 Å (the H I Lyman limit), for key heavy elements (Z > 5) of astrophysical interest. In particular, we focused on transitions observed in the Milky Way ISM, the CGM of the Milky Way and/or other galaxies, and the intergalactic medium.
Cashman, F.(2020). Probing the Interstellar Medium of Galaxies Using Gravitationally Lensed Sight Lines and the Relevant Atomic Physics. (Doctoral dissertation). Retrieved from https://scholarcommons.sc.edu/etd/5925