The COS Legacy Archive Spectroscopy SurveY (CLASSY) Treasury Atlas
Creators: name: Berg, Danielle A.
name: James, Bethan L.
name: King, Teagan
name: Mcdonald, Meaghan
name: Chen, Zuyi
name: Chisholm, John
name: Heckman, Timothy
name: Martin, Crystal L.
name: Stark, Dan P.
name: Team, The Classy
name: :
name: Aloisi, Alessandra
name: AmorÍn, Ricardo O.
name: Arellano-CÓrdova, Karla Z.
name: Bayliss, Matthew
name: Bordoloi, Rongmon
name: Brinchmann, Jarle
name: Charlot, StÉphane
name: Chevallard, Jacopo
name: Clark, Ilyse
name: Erb, Dawn K.
name: Feltre, Anna
name: Hayes, Matthew
name: Henry, Alaina
name: Hernandez, Svea
name: Jaskot, Anne
name: Jones, Tucker
name: Kewley, Lisa J.
name: Kumari, Nimisha
name: Leitherer, Claus
name: Llerena, Mario
name: Maseda, Michael
name: Mingozzi, Matilde
name: Nanayakkara, Themiya
name: Ouchi, Masami
name: Plat, Adele
name: Pogge, Richard W.
name: Ravindranath, Swara
name: Rigby, Jane R.
name: Sanders, Ryan
name: Scarlata, Claudia
name: Senchyna, Peter
name: Skillman, Evan D.
name: Steidel, Charles C.
name: Strom, Allison L.
name: Sugahara, Yuma
name: Wilkins, Stephen M.
name: Wofford, Aida
name: Xu, Xinfeng
Publisher: name: arXiv
Year: 2022
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: Far-ultraviolet (FUV; ~1200-2000 angstroms) 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 JWST 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 COS Legacy Spectroscopic SurveY (CLASSY) treasury and its first high level science product, the CLASSY atlas. CLASSY builds on the HST archive to construct the first high-quality (S/N_1500 &gt;~ 5/resel), high-resolution (R~15,000) FUV spectral database of 45 nearby (0.002 &lt; z &lt; 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 &lt; logM_star(M_sol) &lt; 10.1), star formation rate (-2.0 &lt; log SFR (M_sol/yr) &lt; +1.6), direct gas-phase metallicity (7.0 &lt; 12+log(O/H) &lt; 8.8), ionization (0.5 &lt; O_32 &lt; 38.0), reddening (0.02 &lt; E(B-V &lt; 0.67), and nebular density (10 &lt; n_e (cm^-3) &lt; 1120). CLASSY is biased to UV-bright star-forming galaxies, resulting in a sample that is consistent with z~0 mass-metallicity relationship, but is offset to higher SFRs by roughly 2 dex, similar to z &gt;~2 galaxies. This unique set of properties makes the CLASSY atlas the benchmark training set for star-forming galaxies across cosmic time.
description: Accepted for publication in ApJ