The COS Legacy Archive Spectroscopy Survey (CLASSY) Treasury Atlas

Danielle A. Berg , Bethan L. James , Teagan King , Meaghan Mcdonald , Zuyi Chen , John Chisholm , Timothy Heckman , Crystal L. Martin , Dan P. Stark , Alessandra Aloisi , Ricardo O. Amorín , Karla Z. Arellano-Córdova , Matthew Bayliss , Rongmon Bordoloi , Jarle Brinchmann , Stéphane Charlot (1) , Jacopo Chevallard (1) , Ilyse Clark , Dawn K. Erb , Anna Feltre , Max Gronke , Matthew Hayes , Alaina Henry , Svea Hernandez , Anne Jaskot , Tucker Jones , Lisa J. Kewley , Nimisha Kumari , Claus Leitherer , Mario Llerena , Michael Maseda , Matilde Mingozzi , Themiya Nanayakkara , Masami Ouchi , Adele Plat , Richard W. Pogge , Swara Ravindranath , Jane R. Rigby , Ryan Sanders , Claudia Scarlata , Peter Senchyna , Evan D. Skillman , Charles C. Steidel , Allison L. Strom , Yuma Sugahara , Stephen M. Wilkins , Aida Wofford , Xinfeng Xu

1 IAP - Institut d'Astrophysique de Paris

Far-ultraviolet (FUV; ~1200-2000 Å) spectra are fundamental to our understanding of star-forming galaxies, providing a unique window on massive stellar populations, chemical evolution, feedback processes, and reionization. The launch of the James Webb Space Telescope will soon usher in a new era, pushing the UV spectroscopic frontier to higher redshifts than ever before; however, its success hinges on a comprehensive understanding of the massive star populations and gas conditions that power the observed UV spectral features. This requires a level of detail that is only possible with a combination of ample wavelength coverage, signal-to-noise, spectral-resolution, and sample diversity that has not yet been achieved by any FUV spectral database. We present the Cosmic Origins Spectrograph Legacy Spectroscopic Survey (CLASSY) treasury and its first high-level science product, the CLASSY atlas. CLASSY builds on the Hubble Space Telescope (HST) archive to construct the first high-quality (S/N_{1500 Å} ≳ 5/resel), high-resolution (R ~ 15,000) FUV spectral database of 45 nearby (0.002 < z < 0.182) star-forming galaxies. The CLASSY atlas, available to the public via the CLASSY website, is the result of optimally extracting and coadding 170 archival+new spectra from 312 orbits of HST observations. The CLASSY sample covers a broad range of properties including stellar mass (6.2 < log M _⋆(M _⊙) < 10.1), star formation rate (-2.0 < log SFR (M _⊙ yr^-1) < +1.6), direct gas-phase metallicity (7.0 < 12+log(O/H) < 8.8), ionization (0.5 < O₃₂ < 38.0), reddening (0.02 < E(B - V) < 0.67), and nebular density (10 < n _e (cm^-3) < 1120). CLASSY is biased to UV-bright star-forming galaxies, resulting in a sample that is consistent with the z ~ 0 mass-metallicity relationship, but is offset to higher star formation rates by roughly 2 dex, similar to z ≳ 2 galaxies. This unique set of properties makes the CLASSY atlas the benchmark training set for star-forming galaxies across cosmic time. ^∗ Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

Mots clés: Galaxies; Ultraviolet surveys; Emission line galaxies; Interstellar line absorption; Lyman-alpha galaxies; High-redshift galaxies

Domaines: Planète et Univers [physics]

Danielle A. Berg, Bethan L. James, Teagan King, Meaghan Mcdonald, Zuyi Chen, et al.. The COS Legacy Archive Spectroscopy Survey (CLASSY) Treasury Atlas. The Astrophysical Journal Supplement Series, 2022, 261, ⟨10.3847/1538-4365/ac6c03⟩. ⟨insu-03748234⟩