First Results from the Herschel and ALMA Spectroscopic Surveys of the SMC: The Relationship between [C ii]-bright Gas and CO-bright Gas at Low Metallicity*
Year: 2018
Type: article
Abstract: The Small Magellanic Cloud (SMC) provides the only laboratory to study the structure of molecular gas at high resolution and low metallicity. We present results from the Herschel Spectroscopic Survey of the SMC (HS3), which mapped the key far-IR cooling lines [C ii], [O i], [N ii], and [O iii] in five star-forming regions, and new ALMA 7 m array maps of and with coverage overlapping four of the five HS3 regions. We detect [C ii] and [O i] throughout all of the regions mapped. The data allow us to compare the structure of the molecular clouds and surrounding photodissociation regions using , , [C ii], and [O i] emission at ( pc) scales. We estimate using far-IR thermal continuum emission from dust and find that the CO/[C ii] ratios reach the Milky Way value at high in the centers of the clouds and fall to the Milky Way value in the outskirts, indicating the presence of translucent molecular gas not traced by bright emission. We estimate the amount of molecular gas traced by bright [C ii] emission at low and bright emission at high . We find that most of the molecular gas is at low and traced by bright [C ii] emission, but that faint emission appears to extend to where we estimate that the -to-H i transition occurs. By converting our gas estimates to a CO-to- conversion factor (X CO), we show that X CO is primarily a function of , consistent with simulations and models of low-metallicity molecular clouds.
Source: The Astrophysical Journal
Authors: Katherine E. Jameson, Alberto D. Bolatto, Mark Wolfire, Steven R. Warren, Rodrigo Herrera-Camus, Kevin Croxall, Eric Pellegrini, John-David Smith, Monica Rubio, Remy Indebetouw, Frank P. Israel, Margaret Meixner, Julia Roman-Duval, Jacco Th. van Loon, Erik Muller, Celia Verdugo, Hans Zinnecker, Yoko Okada
Institutions: Australian National University, University of Maryland, College Park, Max Planck Institute for Extraterrestrial Physics, The Ohio State University, Heidelberg University, University of Toledo, University of Chile, National Radio Astronomy Observatory, University of Virginia, Leiden University, Leiden Observatory, Space Telescope Science Institute, Keele University, National Astronomical Observatory of Japan, Atacama Large Millimeter Submillimeter Array, University of Stuttgart, Universidad Autónoma de Chile, University of Cologne
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
Funders: National Science Foundation, National Aeronautics and Space Administration, National Radio Astronomy Observatory, Universities Space Research Association, National Science Council, Korea Astronomy and Space Science Institute, National Astronomical Observatory of Japan, Universität Stuttgart, Comisión Nacional de Investigación Científica y Tecnológica, National Institutes of Natural Sciences
OpenAlex ID: W2782911377