Emission Line Ratios for the Circumgalactic Medium and the “Bimodal” Nature of Galaxies

Zhang, Huanian and Zaritsky, Dennis and Werk, Jessica and Behroozi, Peter (2018) Emission Line Ratios for the Circumgalactic Medium and the “Bimodal” Nature of Galaxies. The Astrophysical Journal, 866 (1). L4. ISSN 2041-8213

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Abstract

We find significantly different diagnostic emission line ratios for the circumgalactic gas associated with galaxies of stellar masses above and below 1010.4 M⊙ using Sloan Digital Sky Survey spectroscopy. Specifically, in a sample of 17,393 galaxies, intersected by 18,535 lines of sight at projected radii between 10 and 50 kpc, we stack measured fluxes for nebular strong emission lines, [O iii] λ5007, Hα, and [N ii] λ6583, and find that the gas surrounding the lower-mass galaxies exhibits similar line ratios to those of gas ionized by star formation and that surrounding the higher-mass galaxies similar to those of gas ionized by active galactic nucleus or shocks. This finding highlights yet another characteristic of galaxies that is distinctly different above and below this stellar mass threshold, but one that is more closely connected to the gas accretion behavior hypothesized to be responsible for this dichotomy.

Item Type: Article
Subjects: Souths Book > Medical Science
Depositing User: Unnamed user with email support@southsbook.com
Date Deposited: 29 Jun 2023 05:20
Last Modified: 24 Jun 2024 05:32
URI: http://research.europeanlibrarypress.com/id/eprint/1309

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