A Sino-German 6cm polarisation survey of the Galactic plane IX. HII regions. (arXiv:1901.00631v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Gao_X/0/1/0/all/0/1">X. Y. Gao</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Reich_P/0/1/0/all/0/1">P. Reich</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hou_L/0/1/0/all/0/1">L. G. Hou</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Reich_W/0/1/0/all/0/1">W. Reich</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Han_J/0/1/0/all/0/1">J. L. Han</a>
Large-scale radio continuum surveys provide data to get insights into the
physical properties of radio sources. HII regions are prominent radio sources
produced by thermal emission of ionised gas around young massive stars. We
identify and analyse HII regions in the Sino-German 6cm polarisation survey of
the Galactic plane. Objects with flat radio continuum spectra together with
infrared and/or Halpha emission are identified to be HII regions. For HII
regions with small apparent sizes, we cross-matched the 6cm small-diameter
source catalogue with the radio HII region catalogue compiled by Paladini and
the infrared HII region catalogue based on the WISE data. Extended HII regions
were identified by overlaying the Paladini and the WISE HII regions onto the
6cm survey images for coincidences by eye. The TT-plot method was employed for
spectral index verification. 401 HII regions were identified and their flux
densities were determined with the Sino-German 6cm survey data. In the surveyed
area, 76 pairs of sources are found to be duplicated in the Paladini HII region
catalogue mainly due to the non-distinction of previous observations with
different angular resolutions, and 78 objects in their catalogue are
misclassified as HII regions, being actually planetary nebulae, supernova
remnants or extragalactic sources that have steep spectra. More than 30 HII
regions and HII region candidates from our 6cm survey data, especially extended
ones, do not have counterparts in the WISE HII region catalogue, among which 9
are identified for the first time. 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 HII regions.
Large-scale radio continuum surveys provide data to get insights into the
physical properties of radio sources. HII regions are prominent radio sources
produced by thermal emission of ionised gas around young massive stars. We
identify and analyse HII regions in the Sino-German 6cm polarisation survey of
the Galactic plane. Objects with flat radio continuum spectra together with
infrared and/or Halpha emission are identified to be HII regions. For HII
regions with small apparent sizes, we cross-matched the 6cm small-diameter
source catalogue with the radio HII region catalogue compiled by Paladini and
the infrared HII region catalogue based on the WISE data. Extended HII regions
were identified by overlaying the Paladini and the WISE HII regions onto the
6cm survey images for coincidences by eye. The TT-plot method was employed for
spectral index verification. 401 HII regions were identified and their flux
densities were determined with the Sino-German 6cm survey data. In the surveyed
area, 76 pairs of sources are found to be duplicated in the Paladini HII region
catalogue mainly due to the non-distinction of previous observations with
different angular resolutions, and 78 objects in their catalogue are
misclassified as HII regions, being actually planetary nebulae, supernova
remnants or extragalactic sources that have steep spectra. More than 30 HII
regions and HII region candidates from our 6cm survey data, especially extended
ones, do not have counterparts in the WISE HII region catalogue, among which 9
are identified for the first time. 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 HII regions.
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