The Stellar Content of Obscured Galactic Giant HII Regions V: G333.1--0.4

Abstract

We present high angular resolution near--infrared images of the obscured Galactic Giant HII (GHII) region G333.1--0.4 in which we detect an OB star cluster. For G333.1--0.4, we find OB stars and other massive objects in very early evolutionary stages, possibly still accreting. We obtained $K$--band spectra of three stars; two show O type photospheric features, while the third has no photospheric features but does show CO 2.3 $\mu$m band--head emission. This object is at least as hot as an early B type star based on its intrinsic luminosity and is surrounded by a circumstellar disc/envelope which produces near infrared excess emission. A number of other relatively bright cluster members also display excess emission in the $K$--band, indicative of disks/envelopes around young massive stars. Based upon the O star photometry and spectroscopy, the distance to the cluster is 2.6 $\pm$ 0.4 kpc, similar to a recently derived kinematic (near side) value. The slope of the $K$--band luminosity function is similar to those found in other young clusters. The mass function slope is more uncertain, and we find $-1.3\pm 0.2<\Gamma <-1.1\pm 0.2$- for stars with M $>5$ M${}_{\odot }$ where the upper an lower limits are calculated independently for different assumptions regarding the excess emission of the individual massive stars. The number of Lyman continuum photons derived from the contribution of all massive stars in the cluster is 0.2 $\times$ $10^{50}$ $s^{-1}$ $<NLyc<1.9$ $\times$ $10^{50}$ $s^{-1}$. The integrated cluster mass is 1.0 $\times$ $10^3$ $M_{\odot }<M_{cluster}<1.3$ $\times$ $10^3$ $M_{\odot }$.

arXiv comment31 pages, including 12 figures and 3 tables. Accepted for publication in the AJ

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• The Massive Star-Forming Regions Omnibus X-Ray Catalog, Second Installment
• The Ionizing Stars of the Galactic Ultra-Compact HII Region G45.45+0.06
• GEMINI near-infrared spectroscopic observations of young massive stars embedded in molecular clouds
• The Stellar Content of Obscured Galactic Giant HII Regions. VII. W3
• Tracing H2 column density with atomic carbon (CI) and CO isotopologues
• Infall, outflow, and turbulence in massive star-forming cores in the G333 giant molecular cloud
• Star-forming Region Sh 2-233IR I. Deep NIR Observations toward the Embedded Stellar Clusters
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• SiO Outflows in the Most Luminous and Massive Protostellar Sources of the Southern Sky
• Mid Infrared View of the High Mass Star Formation Region W51A
• Surveying the Giant HII Regions of the Milky Way with SOFIA: IV. Sgr D, W42, and a Reassessment of the Giant HII Region Census
• The Stellar Content of Obscured Galactic Giant HII Regions. VI: W51A