|CII and Cold Dust as a Tracer of Molecular Gas in Sextans A
|The assembly of star forming molecular clouds is poorly understood in low metallicity galaxies. These galaxies are typically forming stars, and thus must have molecular gas, yet they almost universally lack direct detections of CO. As an alternate means to trace the molecular component of these systems, we propose to use the PACS and SPIRE instruments aboard Herschel to observe both the 158um CII emission line and the cold dust emission between 100-500 microns in the nearby low metallicity galaxy, Sextans A. Recent VLA HI spectral line observations of Sextans A have exceptional spectral resolution (1.3 km-s). This high velocity resolution allows us to reliably decompose the spectra into narrow and broad components which have been associated with the cold and warm neutral gas phases. Coincidence of 158um CII and cold dust emission detected by Herschel with narrow HI spectra will both confirm the existence of a cold neutral medium as well as define the areas most conducive for molecular cloud formation. Combining the proposed Herschel observations with existing HST, VLA, and SPITZER observations will allow usto separate local regions currently forming stars from those which have yet to form them. Understanding the local conditions which are most likely to form molecular clouds is extremely important to the general understanding of star formation, molecular cloud formation, and galaxy assembly-evolution. If our proposed observations confirm that the narrow HI emission is an effective tracer of the more elusive molecular component, then we will have calibrated a method which is generally applicable for all nearby low metallicity galaxies.
|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, 2013, OT2_eskillma_4, SPG v14.2.0. https://doi.org/10.5270/esa-vjl7okz