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A Galactic Sample of Intermediate-Mass Star-Forming Regions: Bridging the High- and Low-mass Regimes
Michael Lundquist University of Wyoming, Laramie, WY, USA | |
| High-mass star-formation might not simply be a scaled-up version of low-mass star formation. The clouds that form these regions have environments that may differ in terms of turbulence and magnetic fields, as well as cloud mass and density. One missing piece in the star-formation paradigm is a study of the star forming regions that constitute the transition from the low-mass to high-mass regimes. We have used IRAS Point Source Catalog color selection to define a flux-limited sample of probable intermediate-mass star-forming regions, where stars up to, but not exceeding, 10 solar masses are being produced. This all-sky sample consists of 984 objects, 676 of which we were able to follow up with 2MASS, WISE, and Spitzer's GLIMPSE surveys to reject contaminating galaxies and derive mid-infrared morphological classifications. This morphological classification effort reveals 4.88% starlike objects, 9.03% filamentary structures, 25.59% galaxies, and 60.50% amorphous blobs that appear to constitute star-forming regions near the Galactic Plane. We find that 50.34% of the blobs are within latitudes |b|<1 degrees and 95.60% are within |b|<5 degrees, while 97.98% of the contaminating galaxies have |b|>5 degrees. Most of the blobs have affiliations with 13CO clouds, Infrared Dark Clouds, and millimeter continuum emission, indicating they are in the early phases of star formation. We utilized deep IR photometry from UKIDSS and 2MASS to generate field star cleaned CMDs and CCDs that were used to select targets for an ongoing spectroscopic investigation at the Wyoming Infrared Observatory (WIRO). Within the eleven candidate IMSFRs currently investigated from WIRO, we obtained classification spectra for 27 stars, finding 0 O-Stars, 13 B-stars, 2 A-stars, and 12 stars F or later. These results begin to validate the IRAS color identification of intermediate-mass star-forming regions and represent the first phase of our larger effort to characterize the stellar populations, ages, locations, and molecular cloud properties of regions at the cusp of massive star formation. | |
| Collaborators: H. Kobulnicky, Univ. Wyoming, USA C. Kerton, Iowa State, USA K. Arvidsson, Adler Planetarium, USA M. Alexander, Univ. Wyoming, USA |
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