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Session 10 - Interstellar Medium and Star Formation.
Display session, Monday, June 08
Atlas Ballroom,

[10.13] The Steward Observatory NIR Survey of UCHII Regions

M. M. Hanson (Steward Obs./U. Cincinnati), K. L. Luhman, G. H. Rieke, V. Burkholder (Steward Obs.)

We have recently completed the first half of a near-infrared imaging and spectroscopic survey of 140 radio selected ultra-compact HII (UCHII) regions using the Steward Observatory Bok 90" telescope. We detect 75% of the UCHII regions using 2 micron spectroscopy to identify the hydrogen Brackett gamma feature. We include a simple nebular analysis using HeI, H_2, and FeII to probe the conditions within a few of the UCHII regions. Simultaneous images taken at 1.65 micron show a number of the UCHII regions lie within a stellar cluster. More recent follow up 2 micron spectra using the Multiple Mirror Telescope has allowed us to determine spectroscopic classifications for some of these stars which may be the ionizing source of the nearby UCHII region. Our results set important limits on the timescales for the formation of the most massive stars and gives us an early glimpse at the local environment within which massive stars are forming.

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