Joint Astrophysics/Space Physics Seminar
"The Diversity of Diffuse Lyα Nebulae around Star-forming Galaxies at High Redshift" by Rui Xue, Ph.D., Post Doctoral Researcher, Department of Physics & Astronomy, The University of Iowa
Abstract: We report diverse sizes of Lyman Alpha Halos (LAHs) measured for normal star-forming galaxies at high redshift. Based on ~1400 galaxies residing in field and dense protocluster environments, we investigate how the LAH characteristics vary with host galaxy large-scale environment and physical properties such as UV luminosity, Lyα luminosity and equivalent widths. The average LAH scalelength, measured for galaxies selected as Lyman Alpha Emitters, is modest at 5-6 kpc (physical); the most UV-luminous galaxies have more extended halos (8-9 kpc). Our analysis largely rules out the presence of very large LAHs around UV-luminous protocluster member galaxies as previously reported based on a similarly significant high-redshift protocluster system. Based on the observed trends of LAH sizes with galaxy parameters, combined with the measured average radial profile of our sample galaxies, we speculate that i) LAHs are primarily powered by central star formation: namely, Lyα photons produced therein escape the interstellar medium and subsequently scatter through the circumgalactic medium (CGM); and ii) the physical conditions of the CGM change with halo mass and/or star formation rates.