Far-ultraviolet (FUV; ~1200-2000{AA}) 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{AA}>~5/resel), high-resolution (R~15000) 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<logM*(M{sun})<10.1), star formation rate (-2.0<logSFR(M{sun}/yr)<+1.6), direct gas-phase metallicity (7.0<12+log(O/H)<8.8), ionization (0.5<O_32<38.0), reddening (0.02<E(B-V)<0.67), and nebular density (10<n_e_(cm-3)~2 galaxies. This unique set of properties makes the CLASSY atlas the benchmark training set for star-forming galaxies across cosmic time.

Cone search capability for table J/ApJS/261/31/classy (Ancillary optical spectra (Table 4), spectroscopy-derived properties (Table 5) and photometry-derived properties (Table 6) for the CLASSY galaxy and nominal and measured spectral resolution of CLASSY coadded spectra (Table 3))

Associated data