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Title: Numerical Simulation of Na I D Absorption-Line Profiles Formed By Galactic Outflows
Authors: Yutong, Duan
Keywords: Text;Physics, Department of;Honors papers;Student research
Issue Date: May-2013
Publisher: Memphis, Tenn. : Rhodes College
Abstract: Galactic outflows may help explain important aspects of galaxy evolution: the regulation of star formation and black hole activity, the energetics of intergalactic medium, the elemental composition of galaxies, and the missing baryons on galaxy scales. The Na I D doublet absorption feature (λλ 5890, 5896) in the visible spectrum is ideal for studying galactic outflows due to a number of reasons: its presence in the visible range after being redshifted (up to z ∼ 0.5), the relatively high abundance of Na in the interstellar medium, and its resolution of a degeneracy between optical depth and covering fraction. We developed a computational model to simulate the Na I D absorption. The program is written in the Interactive Data Language (IDL). The program simulates light that is emitted from the galactic disk, passes through a galactic wind of a given structure, and is absorbed in two upward atomic transitions, resulting in Na I D. The galaxy and outflow gas are characterized by predefined physical parameters. Doppler broadening as the primary physical process responsible for the linewidth is considered along with the turbulence of the gas flow, whereas natural broadening, pressure and collisional broadening, and other radiative transfer processes are neglected. Line-of-sight synthetic spectra of regular wind structures, including spherical, filled biconical, unfilled biconical, and bipolar bubble winds, are generated as well as column density, equivalent-width, and mean bulk velocity maps. By exploring the dependence of simulation results on wind structure and relating theoretical simulations to observational data, we hope to gain insights into the physical properties of galactic outflows.
Description: Permission of the author was given to publish this work. It was submitted to the archives on a CD.
Appears in Collections:Honors Papers

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