Friday, 16th October at 2.00pm at the JAC
Astrophysics Research Centre, Queen's University Belfast
"Observations and Chemical Modeling of Galactic Edge Clouds"
ABSTRACT: Edge Cloud 2 (EC2) is a large molecular cloud at the
Galactic edge. We have detected submillimeter continuum emission and a
large number of molecular transitions in the northern core of EC2 and
constrained the properties of that region with a chemical kinetic
model. We found that the best-fit models are consistent with reduced
elemental abundances and a low dust-to-gas mass ratio. We concluded
that the formation, structure and subsequent chemistry may be the
direct result of SNR shock fronts propagating through EC2 1,000 to
10,000 years ago. We have also shown that the two star forming cores
in EC2 are different, with the southern core having a denser cluster
than the northern core. We have observed a number of molecular lines
in the southern core of EC2, so as to establish if there are chemical
differences between the two regions. To test the importance of shock
chemistry in EC2 we also searched for SiO emission, which could be the
result of an enhanced Si gas-phase abundance due to sputtering of
interstellar grains. We have also examined Edge Cloud 1 (EC1), which
appears to be a chemically less varied environment. The apparent
molecule-poor nature of EC1 demonstrates the characteristics of clouds
that have not had the benefit of SN shocks to stimulate an active
cloud chemistry and star formation.
Galactic Edge Clouds I: Molecular Line Observations and Chemical
Modelling of Edge Cloud 2.
P. M. E. Ruffle, T. J. Millar, H. Roberts, D. A. Lubowich, C. Henkel,
J. Pasachoff and G. Brammer.
ApJ, 671, 1766, December 2007.
Star Formation in the Extreme Outer Galaxy: Digel Cloud 2 Clusters.
Chikako Yasui, Naoto Kobayashi, Alan T. Tokunaga, Hiroshi Terada and
ApJ, 675, 443, March 2008.