CLASSY. XI. Tracing Neutral Gas Properties Using UV Absorption Lines and 21 cm Observations*
Year: 2024
Type: article
Abstract: Rest-frame far-ultraviolet (FUV) observations from JWST are revolutionizing our understanding of the high-z galaxies that drove reionization and the mechanisms by which they accomplished it. To fully interpret these observations, we must be able to diagnose how properties of the interstellar medium (ISM; e.g., column density, covering fraction, and outflow velocity) directly relate to the absorption features produced. Using the high-signal-to-noise and high-resolution FUV spectra of 45 nearby star-forming galaxies from the Cosmic Origins Spectrograph Legacy Spectroscopic Survey, we present the largest uniform, simultaneous characterization of neutral and low-ionization state (LIS) interstellar UV absorption lines (O i, Si ii, S ii, C ii, and Al ii) across a wide range of galaxy properties. We also present 21 cm H i observations for 35 galaxies, multiple of which are gas-poor or nondetected, possibly indicating the onset of a post-starburst phase. We find that our simultaneous one-component Voigt profile fits are capable of accurately modeling the LIS absorption for ∼75% of galaxies, mitigating challenges associated with saturation, infilling, and degeneracies. While the most massive galaxies require additional components, our one-component fits return average properties of the absorbing gas and follow the scaling relations described by a single gas cloud. We explore connections between LIS absorption and direct tracers of the neutral ISM (O i, Lyα, and H i 21 cm), finding that C ii most closely traces the neutral gas trends, while other ions exhibit weaker correlations. Given the challenges with directly observing H i at higher-z, we demonstrate that LIS absorption can be a powerful means to study the neutral ISM and present empirical relationships for predicting neutral gas properties.
Source: The Astrophysical Journal
Authors: Kaelee S. Parker, Danielle A. Berg, Simon Gazagnes, John Chisholm, Bethan L. James, Matthew Hayes, Timothy Heckman, Alaina Henry, Michelle A. Berg, Karla Z. Arellano-Córdova, Xinfeng Xu, Dawn K. Erb, Crystal L. Martin, Weida Hu, Evan D. Skillman, Kristen B. W. McQuinn, Zuyi Chen, Dan P. Stark
Institutions: The University of Texas at Austin, Space Telescope Science Institute, Stockholm University, AlbaNova, Johns Hopkins University, Texas Christian University, Royal Observatory, University of Edinburgh, University of Wisconsin–Milwaukee, University of California, Santa Barbara, Texas A&M University, University of Minnesota, Rutgers, The State University of New Jersey, University of Arizona
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Award: G6920290089
OpenAlex ID: W4405083510