Near-IR observations of UCHII regions

Carlos Alvarez; Markus Feldt; Thomas Henning; Elena Puga; Wolfgang Brandner; Bringfried Stecklum

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Near-IR observations of UCHII regions

Carlos Alvarez·Markus Feldt·Thomas Henning·Elena Puga·Wolfgang Brandner·Bringfried Stecklum

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Abstract

We present adaptive-optics (AO) assisted J, H and K/K' images of 8 UCHII regions taken with the ALFA and ADONIS AO systems at Calar Alto and La Silla observatories. The images show details of the stellar population and the near-IR morphology of UCHIIs with unprecedented resolution. We have searched for the ionizing sources of the regions using near-IR photometry. The spectral type of the ionizing and most luminous stars inferred from our photometry has been compared with spectral type estimates from IRAS and published radio-continuum measurements. We find that the photometric near-IR spectral types are earlier than estimates from radio and IRAS data. This difference is alleviated when stellar spherical models including line blanketing and stellar winds instead of non-LTE plane-parallel models are used to derive the radio- and IRAS-based spectral types. We also made an attempt to correlate the properties of the near-IR ionizing population with MSX data and published CS measurements. No correlation was found. We note that in two of the regions (G309.92+0.48 and G61.48+0.09B1), the best candidate to ionize the region is possibly a super-giant.

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Carlos Alvarez, Markus Feldt, Thomas Henning, Elena Puga, Wolfgang Brandner, Bringfried Stecklum. 2004-07-07. Near-IR observations of UCHII regions. https://arxiv.org/abs/astro-ph/0407139

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