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Improved selection criteria for H ii regions, based on IRAS sources.
- Source :
-
Monthly Notices of the Royal Astronomical Society . May2018, Vol. 476 Issue 3, p3981-3990. 10p. - Publication Year :
- 2018
-
Abstract
- We present new criteria for selecting H ii regions from the Infrared Astronomical Satellite (IRAS) Point Source Catalogue (PSC), based on an H ii region catalogue derived manually from the all-sky Wide-field Infrared Survey Explorer (WISE). The criteria are used to augment the number of H ii region candidates in the Milky Way. The criteria are defined by the linear decision boundary of two samples: IRAS point sources associated with known H ii regions, which serve as the H ii region sample, and IRAS point sources at high Galactic latitudes, which serve as the non-H ii region sample. A machine learning classifier, specifically a support vector machine, is used to determine the decision boundary. We investigate all combinations of four IRAS bands and suggest that the optimal criterion is |$\mathrm{log}\left(F_{60}/F_{12}\right)\geqq \left(-0.19 \times \mathrm{log}\left(F_{100}/F_{25}\right)+ 1.52\right)$|, with detections at 60 and 100 |${\mu}$| m. This selects 3041 H ii region candidates from the IRAS PSC. We find that IRAS H ii region candidates show evidence of evolution on the two-colour diagram. Merging the WISE H ii catalogue with IRAS H ii region candidates, we estimate a lower limit of approximately 10 200 for the number of H ii regions in the Milky Way. [ABSTRACT FROM AUTHOR]
- Subjects :
- *MILKY Way
*GALAXIES
*ASTROPHYSICS
*ASTRONOMY
Subjects
Details
- Language :
- English
- ISSN :
- 00358711
- Volume :
- 476
- Issue :
- 3
- Database :
- Academic Search Index
- Journal :
- Monthly Notices of the Royal Astronomical Society
- Publication Type :
- Academic Journal
- Accession number :
- 132660227
- Full Text :
- https://doi.org/10.1093/mnras/sty518