2025/05/12 by Frances H. Cashman, Cashman, Frances H., Andrew J. Fox +15
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Stellar, planetary, and galactic studies
paper · pdf · doi:10.48550/arxiv.2505.07969
openalex publication_date 2025/05/12 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We present a systematic study of the multi-phase interstellar gas in the Inner Galaxy using HST/STIS absorption spectroscopy of 16 massive stars located at spectroscopic distances between 1.3 and 10 kpc in the region -30^∘\lesssim l \lesssim+30^∘ and -15^∘\lesssim b \lesssim+15^∘. These sight lines probe gas above and below the Sagittarius Carina, Scutum Crux-Centaurus, Norma, and Near 3 kpc spiral arms in a range of z-height from 0 to 1.5 kpc. Along the 16 sight lines, we measure velocity centroids for 800 UV absorption-line components across multiple gas phases (molecular CO, neutral, low ion, and high ion). We find that 619/800 components have velocities that are consistent with a simple model of co-rotation with the disk, indicating that multi-phase gas with disk-like kinematics extends at least 1 kpc into the halo. We present a database of absorption-line parameters that can be used for kinematic modeling of gas flows into and out of the Galactic disk.