OVI, NV, and CIV in the Galactic Halo: I. Velocity-Dependent Ionization Models

Abstract

We explore theoretical models of the ionization ratios of the Li-like absorbers NV, OVI, and CIV, in the Galactic halo. These ions are believed to form in nonequilibrium processes such as shocks, evaporative interfaces, or rapidly cooling gas, all of which trace the dynamics of the interstellar medium. As a useful new diagnostic, we focus on velocity-resolved signatures of several common physical structures: (1) a cooling Galactic fountain flow that rises, cools, and recombines as it returns to the disk; (2) shocks moving toward the observer; (3) a conductive interface with the observer located in the hotter gas. This last geometry occurs with the solar system inside a hot bubble, or when one looks out through the fragmenting top shell of our local bubble blown into the halo as part of the Galactic fountain. In Paper II, these models are compared to ionization-ratio data from FUSE and Hubble Space Telescope.

arXiv commentApJ in press 22 pages, 9 fig

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Cited by in corpus (39)

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• The Far Ultraviolet Spectroscopic Explorer Survey of OVI Emission in the Milky Way
• On the origin of anomalous velocity clouds in the Milky Way
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• Hunting for Metals Using XQ-100 Legacy Survey Composite Spectra
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• Thermal instability in the collisionally cooled gas
• A High Signal-to-Noise HST Spectrum Toward J1009+0713: Precise Absorption Measurements in the CGM of Two Galaxies
• The nearby interstellar medium towards alpha Leo -- UV observations and modeling of a warm cloud within hot gas
• In Search of an Interface between Warm and Hot Gas within the Local Bubble
• The distribution and kinematics of interstellar O~{\small VI} in the Milky Way}
• O~{\small VI} absorption in the Milky Way along the Large Magellanic Cloud lines of sight