The MOSDEF survey: [SIII] as a new probe of evolving interstellar medium conditions

Authors

• Ryan L. Sanders, University of California, Davis
• Tucker Jones, University of California, Davis
• Alice E. Shapley, University of California, Los Angeles
• Naveen A. Reddy, University of California, Riverside
• Mariska Kriek, University of California, Berkeley
• Alison L. Coil, University of California, San Diego
• Brian Siana, University of California, Riverside
• Bahram Mobasher, University of California, Riverside
• Irene Shivaei, The University of Arizona
• Sedona H. Price, Max Planck Institute for Extraterrestrial Physics
• William R. Freeman, University of California, Riverside
• Mojegan Azadi, Harvard-Smithsonian Center for Astrophysics
• Gene C.K. Leung, University of California, San Diego
• Tara Fetherolf, University of California, Riverside
• Tom O. Zick, University of California, Berkeley
• Laura de Groot, The College of Wooster
• Guillermo Barro, University of the PacificFollow
• Francesca M. Fornasini, Harvard-Smithsonian Center for Astrophysics

Document Type

Article

Publication Title

Astrophysical Journal Letters

Department

Physics

ISSN

20418213

Volume

888

Issue

1

DOI

10.3847/2041-8213/ab5d40

First Page

1

Last Page

6

Publication Date

12-31-2019

Abstract

We present measurements of [S III]λλ9069,9531 for a sample of z ∼ 1.5 star-forming galaxies, the first representative sample with measurements of these lines at z ≿ 0.1. We employ the line ratio S32 ≡ [S III]λλ9069,9531/[S II]λλ6716,6731 as a novel probe of evolving interstellar medium (ISM) conditions. Since this ratio includes the low-ionization line [S II], it is crucial that the effects of diffuse ionized gas (DIG) on emission-line ratios be accounted for in z ∼ 0 galaxy spectra, or else that comparisons be made to samples of local H II regions in which DIG emission is not present. We find that S32 decreases with increasing stellar mass at both z ∼ 1.5 and z ∼ 0, but with a shallow slope suggesting S32 has a weak dependence on metallicity, in contrast with [O III]/[O II] that displays a strong metallicity dependence. As a result, S32 only mildly evolves with redshift at fixed stellar mass. The z ∼ 1.5 sample is systematically offset toward lower S32 and higher [S II]/Hα at fixed [O III]/Hβ relative to z = 0 H II regions. We find that such trends can be explained by a scenario in which the ionizing spectrum is harder at fixed O/H with increasing redshift, but are inconsistent with an increase in ionization parameter at fixed O/H. This analysis demonstrates the advantages of expanding beyond the strongest rest-optical lines for evolutionary studies, and the particular utility of [S III] for characterizing evolving ISM conditions and stellar compositions. These measurements provide a basis for estimating [S III] line strengths for high-redshift galaxies, a line that the James Webb Space Telescope will measure out to z ∼ 5.5.

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 International License.

Recommended Citation

Sanders, Ryan L.; Jones, Tucker; Shapley, Alice E.; Reddy, Naveen A.; Kriek, Mariska; Coil, Alison L.; Siana, Brian; Mobasher, Bahram; Shivaei, Irene; Price, Sedona H.; Freeman, William R.; Azadi, Mojegan; Leung, Gene C.K.; Fetherolf, Tara; Zick, Tom O.; de Groot, Laura; Barro, Guillermo; and Fornasini, Francesca M., "The MOSDEF survey: [SIII] as a new probe of evolving interstellar medium conditions" (2019). Pacific Faculty Work. 292.
https://scholarlycommons.pacific.edu/all-faculty/292