The Structure of the Local Interstellar Medium. VI. New MgII, FeII, and MnII Observations Toward Stars Within 100 Parsecs

Abstract

We analyze high-resolution spectra obtained with the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope toward 34 nearby stars (<100 pc) to record MgII, FeII and MnII absorption due to the local interstellar medium (LISM). Observations span the entire sky, probing previously unobserved regions of the LISM. We detected one to six individual absorption components along any given sight line, and the number of absorbers roughly correlates with the pathlength. This high-resolution near-ultraviolet (NUV) spectroscopic survey was specifically designed for sight lines with existing far-UV (FUV) observations. The FUV spectra include many intrinsically broad absorption lines (i.e., of low atomic mass ions) and often observed at medium resolution. The LISM NUV narrow-line absorption component structure presented here can be used to more accurately interpret the archival FUV observations. As an example of this synergy, we present a new analysis of the temperature and turbulence along the line of sight toward epsilon Ind. The new observations of LISM velocity structure are also critical in the interpretation of astrospheric absorption derived from fitting the saturated HI Lyman-alpha profile. As an example, we reanalyze the spectrum of lambda And and find that this star likely does have an astrosphere. Two stars in the sample that have circumstellar disks (49 Cet and HD141569) show evidence for absorption due to disk gas. Finally, the substantially increased number of sight lines is used to test and refine the three-dimensional kinematic model of the LISM, and search for previously unidentified clouds within the Local Bubble. We find that every prediction made by the Redfield & Linsky (2008) kinematic model of the LISM is confirmed by an observed component in the new lines of sight.