AAS 197, January 2001
Session 5. Molecular Clouds and Cloud Cores
Display, Monday, January 8, 2001, 9:30am-7:00pm, Exhibit Hall

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[5.12] The MSX-CGPS Search for Dissociating Stars

C. R. Kerton (DRAO - HIA - NRC Canada), CGPS Dissociating Stars Project Team

Young embedded main sequence B1--B5 stars are expected to have large dissociated HI zones around them relative to the size of their HII zones. Observationally these ``dissociating'' stars are expected to be IRAS point sources, be associated with molecular clouds, have associated HI emission, and have weak radio continuum emission. The Canadian Galactic Plane Survey (CGPS) data base is an ideal tool for searching for these objects. It consists of uniform 1' resolution HI, radio continuum (1420 and 408 MHz), IRAS (all bands, HIRES processed), and CO (J=1--0) data spanning l=75 -- 145, b = -3 -- +5 degrees. To date, searches have been hampered primarily because of the difficulty in detecting the HI emission signature of these objects in the HI data cubes.

We have found that known dissociating stars are very bright features in the Midcourse Space Experiment (MSX) Band A (7--11~\mum) images due to strong PAH emission associated with the neutral gas surrounding the star. The 20'' spatial resolution and regular beam shape (cf. IRAS) of the MSX data allow one to determine the expected morphology of the associated HI emission. Observations of the currently known dissociating stars will be shown to demonstrate the morphological similarity of the HI and MSX Band A emission.

A new search technique integrating MSX and CGPS data has been developed. New candidates are first identified using the MSX Band A data. IRAS colors are calculated for the object and the CGPS CO and HI data are then examined for associated emission. If a detection is made these data provide information about the stellar environment and distance, and the IRAS data then are used to provide a luminosity estimate. New candidate dissociating stars found using this technique will be presented.

This research is supported by NRC Canada and through grants from NSERC Canada.

The author(s) of this abstract have provided an email address for comments about the abstract: charles.kerton@nrc.ca

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