| Description |
We propose a spectroscopic survey of the Small Magellanic Cloud (SMC)designed to measure the impact of metallicity on the interstellarmedium and specifically to determine the mass and structure ofmolecular gas residing in a CO-dark phase. The SMC is the nearesttruly low-metallicity, actively star-forming galaxy and shows the bestevidence of any galaxy of being dominated by CO-dark H2 gas. Thismakes the SMC an absolutely unique target and the best source to studyhow the H2 reservoir, the relation between star formation and H2, andthe relation between H2 and CO are affected by metallicity. These arekey problems with far-reaching implications for the evolution of thestar formation across cosmic time and the interpretation ofhigh-redshift observations in the ALMA era. Our survey consistsspectral mapping with FTS+PACS (CII, OI, NII, OIII) of 5regions selected to span a wide range in r^ant parameter space andenable a clean and precise measurement of the abundance of CO-darkmolecular gas. This rich dataset will have lasting legacy value andaddress a key gap in the Herschel legacy, enabling studies in a widerange of other topics. Moreover, the coIs will publicly distribute thedata products 18 months after the end of observations. The team haveextensive leading expertise on these science topics, as well asmodeling and data reduction. |
