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Session 66 - Galaxies.
Display session, Thursday, June 11
Atlas Ballroom,
While numerous studies have examined the nature and role of giant molecular clouds (GMCs) in the Milky Way, the role of GMCs in external galaxies is not yet well understood. A study of GMCs in external galaxies can address the fundamental questions of whether the molecular ISM in external galaxies is organized differently than in the Milky Way and whether GMCs play the same central role in massive star formation as in the Milky Way. Moreover, in an external galaxy, we can determine whether the dust lanes correspond to GMCs or diffuse gas and investigate theories of cloud formation and destruction by studying GMC properties and GMC location relative to the spiral arms and star forming regions.
Since typical GMCs (D 50 pc) can be resolved only in nearby Local Group galaxies, we have mosaicked seven fields in the northeastern spiral arm of the nearby Local Group spiral M31 (Andromeda) in the CO J=(1-0) emission line using the BIMA millimeter Array. Our synthesized beam of 7\arcsec allows us to resolve structures on size scales of 20 pc. In the 0.8 x 3.6 kpc mosaicked region, we have detected over 20 GMCs, most of which lie along the spiral arm dust lane or in the vicinity of HII regions. Preliminary analysis of the data reveals not a single bright GMC (compared to Galactic GMCs) in the surveyed region; the most massive GMC has a virial mass less than 6 x 10^5 M_\sun. In this poster, we present the properties of the observed GMCs and compare them to those of GMCs in the Milky Way and other Local Group galaxies.
