CLASSY II: A technical Overview of the COS Legacy Archive Spectroscopic SurveY
Abstract
The COS Legacy Archive Spectroscopic SurveY (CLASSY) is designed to provide the community with a spectral atlas of 45 nearby star-forming galaxies which were chosen to cover similar properties as those seen at high-z (z>6). The prime high level science product of CLASSY is accurately coadded UV spectra, ranging from ~1000-2000A, derived from a combination of archival and new data obtained with HST's Cosmic Origins Spectrograph (COS). This paper details the multi-stage technical processes of creating this prime data product, and the methodologies involved in extracting, reducing, aligning, and coadding far-ultraviolet (FUV) and near-ultraviolet (NUV) spectra. We provide guidelines on how to successfully utilize COS observations of extended sources, despite COS being optimized for point sources, and best-practice recommendations for the coaddition of UV spectra in general. Moreover, we discuss the effects of our reduction and coaddition techniques in the scientific application of the CLASSY data. In particular, we find that accurately accounting for flux calibration offsets can affect the derived properties of the stellar populations, while customized extractions of NUV spectra for extended sources are essential for correctly diagnosing the metallicity of galaxies via CIII] nebular emission. Despite changes in spectral resolution of up to ~25% between individual datasets (due to changes in the COS line spread function), no adverse affects were observed on the difference in velocity width and outflow velocities of isolated absorption lines when measured in the final combined data products, owing in-part to our signal-to-noise regime of S/N<20.
Keywords
Cite
@article{arxiv.2206.01224,
title = {CLASSY II: A technical Overview of the COS Legacy Archive Spectroscopic SurveY},
author = {Bethan L. James and Danielle A. Berg and Teagan King and David J. Sahnow and Matilde Mingozzi and John Chisholm and Timothy Heckman and Crystal L. Martin and Dan P. Stark and The Classy Team and : and Alessandra Aloisi and Ricardo O. Amorín and Karla Z. Arellano-Córdova and Matthew Bayliss and Rongmon Bordoloi and Jarle Brinchmann and Stéphane Charlot and Jacopo Chevallard and Ilyse Clark and Dawn K. Erb and Anna Feltre and Matthew Hayes and Alaina Henry and Svea Hernandez and Anne Jaskot and Tucker Jones and Lisa J. Kewley and Nimisha Kumari and Claus Leitherer and Mario Llerena and Michael Maseda and Themiya Nanayakkara and Masami Ouchi and Adele Plat and Richard W. Pogge and Swara Ravindranath and Jane R. Rigby and Ryan Sanders and Claudia Scarlata and Peter Senchyna and Evan D. Skillman and Charles C. Steidel and Allison L. Strom and Yuma Sugahara and Stephen M. Wilkins and Aida Wofford and Xinfeng Xu},
journal= {arXiv preprint arXiv:2206.01224},
year = {2022}
}
Comments
31 pages, 17 figures, accepted for publication in ApJS