3 research outputs found
Bipolar HII regions - Morphology and star formation in their vicinity - I - G319.8800.79 and G010.3200.15
Our goal is to identify bipolar HII regions and to understand their
morphology, their evolution, and the role they play in the formation of new
generations of stars. We use the Spitzer and Herschel Hi-GAL surveys to
identify bipolar HII regions. We search for their exciting star(s) and estimate
their distances using near-IR data. Dense clumps are detected using
Herschel-SPIRE data. MALT90 observations allow us to ascertain their
association with the central HII region. We identify Class 0/I YSOs using their
Spitzer and Herschel-PACS emissions. These methods will be applied to the
entire sample of candidate bipolar HII regions. This paper focuses on two
bipolar HII regions, one interesting in terms of its morphology,
G319.8800.79, and one in terms of its star formation, G010.3200.15. Their
exciting clusters are identified and their photometric distances estimated to
be 2.6 kpc and 1.75 kpc, respectively. We suggest that these regions formed in
dense and flat structures that contain filaments. They have a central ionized
region and ionized lobes perpendicular to the parental cloud. The remains of
the parental cloud appear as dense (more than 10^4 per cm^3) and cold (14-17 K)
condensations. The dust in the PDR is warm (19-25 K). Dense massive clumps are
present around the central ionized region. G010.32-00.14 is especially
remarkable because five clumps of several hundred solar masses surround the
central HII region; their peak column density is a few 10^23 per cm^2, and the
mean density in their central regions reaches several 10^5 per cm^3. Four of
them contain at least one massive YSO; these clumps also contain extended green
objects and Class II methanol masers. This morphology suggests that the
formation of a second generation of massive stars has been triggered by the
central bipolar HII region. It occurs in the compressed material of the
parental cloud.Comment: 32 pages, 28 figures, to be published in A&