|Characterizing Molecular Clouds at Low Metallicity
|Molecular gas is difficult to detect from traditional millimeter CO transitions in dwarf galaxies below a certain metallicity. Yet, there is evidence for lots of molecular H_2 in these galaxies. Fortunately, Photo-dissociation Regions are a better tracer of the molecular material in low metallicity systems. In metal-poor galaxies, PDRs dominate the molecular core where CO is found, and in the current paradigm the PDR grows and the core shrinks as metallicity decreases. Thus, we expect critical differences in the molecular clouds of dwarfs compared to spirals, with the differences becoming more extreme with lower metallicity. Yet, understanding these differences and their consequences to star formation is essential to understanding the processes that drive star formation at low metallicities. Therefore, we propose to observe the PDRs in 5 regions in 5 typical metal-poor dwarf galaxies spanning a range in oxygen abundance. We will use these observations to characterize the molecular gas, examine the correspondence between the molecular clouds and the atomic gas and star formation characteristics, and determine the characteristics of the atomic ISM that are necessary for the formation of these dense molecular clouds. We will also test the molecular cloud structure paradigm as a function of metallicity.
|Herschel Spectroscopic Observations of Little Things Dwarf Galaxies . Cigan Phil et al. . The Astronomical Journal, Volume 151, Issue 1, article id. 14, 25 pp. (2016). . 151 . 10.3847/0004-6256/151/1/14 . 2016AJ....151...14C ,
|Herschel was launched on 14 May 2009! It is the fourth 'cornerstone' mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 µm range, bridging the gap between earlier infrared space missions and groundbased facilities.
|Publisher And Registrant
|European Space Agency
|European Space Agency, 2012, OT1_dhunter_3, SPG v14.2.0. https://doi.org/10.5270/esa-91y4pj5