7 mm continuum observations of ultra compact HII regions

Abstract

Ultra compact HII (UCHII) regions are indicators of high-mass star formation sites and are distributed mainly in the Galactic plane. We intend to investigate the possible contribution of the forthcoming ESA Planck mission to the science of UCHII regions by evaluating the possibility of detecting UCHIIs that are bright in the radio regime. We performed new 7 mm observations of a sample of UCHII regions. For each source in our sample, the free-free radio spectrum has been modeled. Along with far-IR measurements, our spectra allow us to estimate the flux densities of the sources in the millimeter and sub-millimeter bands. The possibility of Planck detecting the selected sources can be assessed by comparing the estimated flux densities to the expected sensitivity in each Planck channel. We conclude that, in the case of the present sample, located close to the Galactic center, Planck will have a very low detection rate. In contrast, assuming that our sample is representative of the whole UCHII-region population, we derive a very high probability of detecting this kind of source with Planck if located instead close to the anticenter.

8 pages, 6 figures, accepted for publication on Astronomy and Astrophysics

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• Multiwavelength Observations of the Gamma-Ray Blazar PKS 0528+134 in Quiescence
• The Infrared and Radio Fluxes Densities of Galactic HII Regions
• CO-to-H${}_2$ Conversion and Spectral Column Density in Molecular Clouds: The Vriability of $X_{\mathrm{CO}}$ Factor
• The Coordinated Radio and Infrared Survey for High-mass Star Formation. IV: A new radio selected sample of compact Galactic Planetary Nebulae
• The Southern HII Region Discovery Survey. II. The Full Catalog
• A search for radio jets from massive young stellar objects. Association of radio jets with H2O and CH3OH masers
• SCORPIO-II: Spectral indices of weak Galactic radio sources
• Discovery and origin of the radio emission from the multiple stellar system KQVel
• Twenty years of blazar monitoring with the INAF radio telescopes