| Description |
We propose a spectroscopic survey of the Small Magellanic Cloud (SMC) designed to measure the impact of metallicity on the interstellar medium and specifically to determine the mass and structure of molecular gas residing in a CO-dark phase. The SMC is the nearest truly low-metallicity, actively star-forming galaxy and shows the best evidence of any galaxy of being dominated by CO-dark H2 gas. This makes the SMC an absolutely unique target and the best source to study how the H2 reservoir, the relation between star formation and H2, and the relation between H2 and CO are affected by metallicity. These are key problems with far-reaching implications for the evolution of the star formation across cosmic time and the interpretation of high-redshift observations in the ALMA era. Our survey consists spectral mapping with FTS+PACS ([CII], [OI], [NII], [OIII]) of 5 regions selected to span a wide range in r^ant parameter space and enable a clean and precise measurement of the abundance of CO-dark molecular gas. This rich dataset will have lasting legacy value and address a key gap in the Herschel legacy, enabling studies in a wide range of other topics. Moreover, the coIs will publicly distribute the data products 18 months after the end of observations. The team have extensive leading expertise on these science topics, as well as modeling and data reduction. |
