The Astrophysical Journal (Jan 2024)
CLASSY. VIII. Exploring the Source of Ionization with UV Interstellar Medium Diagnostics in Local High-z Analogs
- Matilde Mingozzi,
- Bethan L. James,
- Danielle A. Berg,
- Karla Z. Arellano-Córdova,
- Adele Plat,
- Claudia Scarlata,
- Alessandra Aloisi,
- Ricardo O. Amorín,
- Jarle Brinchmann,
- Stéphane Charlot,
- John Chisholm,
- Anna Feltre,
- Simon Gazagnes,
- Matthew Hayes,
- Timothy Heckman,
- Svea Hernandez,
- Lisa J. Kewley,
- Nimisha Kumari,
- Claus Leitherer,
- Crystal L. Martin,
- Michael Maseda,
- Themiya Nanayakkara,
- Swara Ravindranath,
- Jane R. Rigby,
- Peter Senchyna,
- Evan D. Skillman,
- Yuma Sugahara,
- Stephen M. Wilkins,
- Aida Wofford,
- Xinfeng Xu
Affiliations
- Matilde Mingozzi
- ORCiD
- Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA ; [email protected]; AURA for ESA, Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA
- Bethan L. James
- ORCiD
- AURA for ESA, Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA
- Danielle A. Berg
- ORCiD
- Department of Astronomy, The University of Texas at Austin , 2515 Speedway, Stop C1400, Austin, TX 78712, USA
- Karla Z. Arellano-Córdova
- ORCiD
- Institute for Astronomy, University of Edinburgh , Royal Observatory, Edinburgh, EH9 3HJ, UK
- Adele Plat
- ORCiD
- Institute for Physics , Laboratory for Galaxy Evolution, EPFL, Observatoire de Sauverny, Chemin Pegasi 51, 1290 Versoix, Switzerland
- Claudia Scarlata
- ORCiD
- Minnesota Institute for Astrophysics, University of Minnesota , 116 Church Street SE, Minneapolis, MN 55455, USA
- Alessandra Aloisi
- ORCiD
- Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA ; [email protected]
- Ricardo O. Amorín
- ORCiD
- ARAID Foundation. Centro de Estudios de Física del Cosmos de Aragón (CEFCA), Unidad Asociada al CSIC , Plaza San Juan 1, E–44001 Teruel, Spain; Departamento de Astronomía, Universidad de La Serena , Avenida Juan Cisternas 1200 Norte, La Serena 1720236, Chile
- Jarle Brinchmann
- ORCiD
- Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto , CAUP, Rua das Estrelas, PT4150-762 Porto, Portugal
- Stéphane Charlot
- ORCiD
- Sorbonne Université , CNRS, UMR7095, Institut d’Astrophysique de Paris, F-75014, Paris, France
- John Chisholm
- ORCiD
- Department of Astronomy, The University of Texas at Austin , 2515 Speedway, Stop C1400, Austin, TX 78712, USA
- Anna Feltre
- ORCiD
- INAF—Osservatorio Astrofisico di Arcetri , Largo E. Fermi 5, I-50157 Firenze, Italy
- Simon Gazagnes
- ORCiD
- Department of Astronomy, The University of Texas at Austin , 2515 Speedway, Stop C1400, Austin, TX 78712, USA
- Matthew Hayes
- ORCiD
- Stockholm University , Department of Astronomy and Oskar Klein Centre for Cosmoparticle Physics, AlbaNova University Centre, SE-10691, Stockholm, Sweden
- Timothy Heckman
- ORCiD
- Center for Astrophysical Sciences, Department of Physics & Astronomy, Johns Hopkins University , Baltimore, MD 21218, USA
- Svea Hernandez
- ORCiD
- AURA for ESA, Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA
- Lisa J. Kewley
- ORCiD
- Research School of Astronomy and Astrophysics, Australian National University , Cotter Road, Weston Creek, ACT 2611, Australia; ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Canberra, ACT 2611, Australia
- Nimisha Kumari
- ORCiD
- AURA for ESA, Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA
- Claus Leitherer
- ORCiD
- Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA ; [email protected]
- Crystal L. Martin
- ORCiD
- Department of Physics, University of California , Santa Barbara, Santa Barbara, CA 93106, USA
- Michael Maseda
- ORCiD
- Department of Astronomy, University of Wisconsin-Madison , 475 North Charter Street, Madison, WI 53706 USA
- Themiya Nanayakkara
- ORCiD
- Swinburne University of Technology , Melbourne, Victoria, Australia
- Swara Ravindranath
- ORCiD
- Observational Cosmology Lab , Code 665, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA
- Jane R. Rigby
- ORCiD
- Observational Cosmology Lab , Code 665, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA
- Peter Senchyna
- ORCiD
- Carnegie Observatories , 813 Santa Barbara Street, Pasadena, CA 91101, USA
- Evan D. Skillman
- ORCiD
- Minnesota Institute for Astrophysics, University of Minnesota , 116 Church Street SE, Minneapolis, MN 55455, USA
- Yuma Sugahara
- ORCiD
- Institute for Cosmic Ray Research, The University of Tokyo , Kashiwa-no-ha, Kashiwa 277-8582, Japan; National Astronomical Observatory of Japan , 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; Waseda Research Institute for Science and Engineering, Faculty of Science and Engineering, Waseda University , 3-4-1, Okubo, Shinjuku, Tokyo 169-8555, Japan
- Stephen M. Wilkins
- ORCiD
- Astronomy Centre, University of Sussex , Falmer, Brighton BN1 9QH, UK
- Aida Wofford
- ORCiD
- Instituto de Astronomía, Universidad Nacional Autónoma de México , Unidad Académica en Ensenada, Km 103 Carr. Tijuana-Ensenada, Ensenada 22860, México
- Xinfeng Xu
- ORCiD
- Department of Physics and Astronomy, Northwestern University , 2145 Sheridan Road, Evanston, IL 60208, USA; Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University , 1800 Sherman Avenue, Evanston, IL 60201, USA
- DOI
- https://doi.org/10.3847/1538-4357/ad1033
- Journal volume & issue
-
Vol. 962,
no. 1
p. 95
Abstract
In the current JWST era, rest-frame UV spectra play a crucial role in enhancing our understanding of the interstellar medium (ISM) and stellar properties of the first galaxies in the epoch of reionization ( z > 6). Here, we compare well-known and reliable optical diagrams sensitive to the main ionization source (i.e., star formation, SF; active galactic nuclei, AGN; and shocks) to UV counterparts proposed in the literature—the so-called “UV–BPT diagrams”—using the HST COS Legacy Archive Spectroscopic SurveY (CLASSY), which is the largest high-quality, high-resolution, and broad-wavelength range atlas of far-UV spectra for 45 local star-forming galaxies. In particular, we explore where CLASSY UV line ratios are located in the different UV diagnostic plots, taking into account state-of-the-art photoionization and shock models, and, for the first time, the measured ISM and stellar properties (e.g., gas-phase metallicity, ionization parameter, carbon abundance, and stellar age). We find that the combination of C iii ] λ λ 1907,9 He ii λ 1640 and O iii ] λ 1666 can be a powerful tool to separate between SF, shocks, and AGN at subsolar metallicities. We also confirm that alternative diagrams without O iii ] λ 1666 still allow us to define an SF-locus, with some caveats. Diagrams including C iv λ λ 1548,51 should be taken with caution given the complexity of this doublet profile. Finally, we present a discussion detailing the ISM conditions required to detect UV emission lines, visible only in low gas-phase metallicity (12 + log(O/H) ≲ 8.3) and high ionization parameter (log( U ) ≳ −2.5) environments. Overall, CLASSY and our UV toolkit will be crucial in interpreting the spectra of the earliest galaxies that JWST is currently revealing.
Keywords
- Dwarf galaxies
- Ultraviolet astronomy
- Galaxy chemical evolution
- Galaxy spectroscopy
- High-redshift galaxies
- Emission line galaxies
