SDSS-IV MaNGA: Modeling the spectral line-spread function to subpercent accuracy

David R. Law, Kyle B. Westfall, Matthew A. Bershady, Michele Cappellari, Renbin Yan, Francesco Belfiore, Dmitry Bizyaev, Joel R. Brownstein, Yanping Chen, Brian Cherinka, Niv Drory, Daniel Lazarz, Shravan Shetty

Research output: Contribution to journalArticlepeer-review

20 Scopus citations

Abstract

The Sloan Digital Sky Survey IV Mapping Nearby Galaxies at APO (MaNGA) program has been operating from 2014 to 2020, and has now observed a sample of 9269 galaxies in the low redshift universe (z ∼ 0.05) with integral-field spectroscopy. With rest-optical (λλ0.36-1.0 μm) spectral resolution R ∼ 2000 the instrumental spectral line-spread function (LSF) typically has 1σ width of about 70 km s−1, which poses a challenge for the study of the typically 20-30 km s−1 velocity dispersion of the ionized gas in present-day disk galaxies. In this contribution, we present a major revision of the MaNGA data pipeline architecture, focusing particularly on a variety of factors impacting the effective LSF (e.g., under-sampling, spectral rectification, and data cube construction). Through comparison with external assessments of the MaNGA data provided by substantially higher-resolution R ∼ 10,000 instruments, we demonstrate that the revised MPL-10 pipeline measures the instrumental LSF sufficiently accurately (≤0.6% systematic, 2% random around the wavelength of Hα) that it enables reliable measurements of astrophysical velocity dispersions σ ∼ 20 km s−1 for spaxels with emission lines detected at signal-to-noise ratio > 50. Velocity dispersions derived from [O II], Hβ, [O III], [N II], and [S II] are consistent with those derived from Hα to within about 2% at σ > 30 km s−1. Although the impact of these changes to the estimated LSF will be minimal at velocity dispersions greater than about 100 km s−1, scientific results from previous data releases that are based on dispersions far below the instrumental resolution should be reevaluated.

Original languageEnglish
Article number52
JournalAstronomical Journal
Volume161
Issue number2
DOIs
StatePublished - Jan 6 2021

Bibliographical note

Funding Information:
Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S.

Funding Information:
D.R.L. appreciates productive discussions with Jeb Bailey, and constructive suggestions by the anonymous referee. R.Y. and D.L. acknowledge support by NSF AST-1715898. M.A.B. acknowledges NSF Awards AST-1517006 and AST-1814682.

Funding Information:
We therefore conclude that the MaNGA data products provided with internal release MPL-10 are sufficiently well calibrated to allow scientific analysis of the ionized-gas velocity dispersions down to about 20 km s−1 with sufficient care and attention to detail. Previous public MaNGA data releases (DR13, DR14, DR15) exhibit few-percent systematic biases in the instrumental LSF however (see Figure 13) that will complicate efforts to perform such analyses. Updated MaNGA products will be released publicly in DR17. D.R.L. appreciates productive discussions with Jeb Bailey, and constructive suggestions by the anonymous referee. R.Y. and D.L. acknowledge support by NSF AST-1715898. M.A.B. acknowledges NSF Awards AST-1517006 and AST-1814682. Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. SDSS-IV acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. The SDSS website is www.sdss.org. SDSS-IV is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS Collaboration including the Brazilian Participation Group, the Carnegie Institution for Science, Carnegie Mellon University, the Chilean Participation Group, the French Participation Group, Harvard-Smithsonian Center for Astrophysics, Instituto de Astrofísica de Canarias, The Johns Hopkins University, Kavli Institute for the Physics and Mathematics of the Universe (IPMU)/University of Tokyo, the Korean Participation Group, Lawrence Berkeley National Laboratory, Leibniz Institut für Astrophysik Potsdam (AIP), Max-Planck-Institut für Astronomie (MPIA Heidelberg), Max-Planck-Institut für Astrophysik (MPA Garching), Max-Planck-Institut für Extraterrestrische Physik (MPE), National Astronomical Observatories of China, New Mexico State University, New York University, University of Notre Dame, Observatário Nacional/MCTI, The Ohio State University, Pennsylvania State University, Shanghai Astronomical Observatory, United Kingdom Participation Group, Universidad Nacional Autónoma de México, University of Arizona, University of Colorado Boulder, University of Oxford, University of Portsmouth, University of Utah, University of Virginia, University of Washington, University of Wisconsin, Vanderbilt University, and Yale University.

Publisher Copyright:
© 2021. The American Astronomical Society. All rights reserved.

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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