文章基本信息

标题：A Sino-German λ6 cm polarisation survey of the Galactic plane
其他标题：IX. H IIregions⋆
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作者：P. Reich ; W. Reich
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2019
卷号：623
DOI：10.1051/0004-6361/201834092
语种：English
出版社：EDP Sciences
摘要：Context. Large-scale radio continuum surveys provide data to get insights into the physical properties of radio sources. H IIregions are prominent radio sources produced by thermal emission of ionised gas around young massive stars.Aims. We identify and analyse H IIregions in the Sino-Germanλ6 cm polarisation survey of the Galactic plane.Methods. Objects with flat radio continuum spectra together with infrared and/or Hαemission were identified as H IIregions. For H IIregions with small apparent sizes, we cross-matched theλ6 cm small-diameter source catalogue with the radio H IIregion catalogue compiled by Paladini and the infrared H IIregion catalogue based on the WISE data. Effelsbergλ21 cm andλ11 cm continuum survey data were used to determine source spectra. High angular resolution data from the Canadian Galactic Plane Survey and the NRAO VLA Sky Survey were used to solve the confusion when low angular resolution observations were not sufficient. Extended H IIregions were identified by eye by overlaying the Paladini and the WISE H IIregions onto theλ6 cm survey images for coincidences. The TT-plot method was employed for spectral index verification.Results. A total of 401 H IIregions were identified and their flux densities were determined with the Sino-Germanλ6 cm survey data. In the surveyed area, 76 pairs of sources are found to be duplicated in the Paladini H IIregion catalogue, mainly due to the non-distinction of previous observations with different angular resolutions and 78 objects in their catalogue are misclassified as H IIregions, being actually planetary nebulae, supernova remnants, or extragalactic sources that have steep spectra. More than 30 H IIregions and H IIregion candidates from ourλ6 cm survey data, especially extended ones, do not have counterparts in the WISE H IIregion catalogue, of which 9 are identified for the first time. Our results imply that some more Galactic H IIregions still await to be discovered and the combination of multi-domain observations is important for H IIregion identification. Based on the newly derived radio continuum spectra and the evidence of infrared emission, the previously identified SNRs G11.1−1.0, G20.4+0.1 and G16.4−0.5 are believed to be H IIregions.
关键词：enH II regionsradio continuum: generalmethods: observational