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Shape Analysis of HII Regions - I. Statistical Clustering

Campbell-White, J., Froebrich, Dirk, Kume, Alfred (2018) Shape Analysis of HII Regions - I. Statistical Clustering. Monthly Notices of the Royal Astronomical Society, 477 (4). pp. 5486-5500. ISSN 0035-8711. (doi:10.1093/mnras/sty954) (KAR id:66781)

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We present here our shape analysis method for a sample of 76 Galactic HII regions from MAGPIS 1.4 GHz data. The main goal is to determine whether physical properties and initial conditions of massive star cluster formation is linked to the shape of the regions. We outline a systematic procedure for extracting region shapes and perform hierarchical clustering on the shape data. We identified six groups that categorise HII regions by common morphologies. We confirmed the validity of these groupings by bootstrap re-sampling and the ordinance technique multidimensional scaling. We then investigated associations between physical parameters and the assigned groups. Location is mostly independent of group, with a small preference for regions of similar longitudes to share common morphologies. The shapes are homogeneously distributed across Galactocentric distance and latitude. One group contains regions that are all younger than 0.5 Myr and ionised by low- to intermediate-mass sources. Those in another group are all driven by intermediate- to high-mass sources. One group was distinctly separated from the other five and contained regions at the surface brightness detection limit for the survey. We find that our hierarchical procedure is most sensitive to the spatial sampling resolution used, which is determined for each region from its distance. We discuss how these errors can be further quantified and reduced in future work by utilising synthetic observations from numerical simulations of HII regions. We also outline how this shape analysis has further applications to other diffuse astronomical objects.

Item Type: Article
DOI/Identification number: 10.1093/mnras/sty954
Uncontrolled keywords: Astrophysics - Astrophysics of Galaxies, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Solar and Stellar Astrophysics
Subjects: Q Science > QB Astronomy > QB460 Astrophysics
Divisions: Divisions > Division of Computing, Engineering and Mathematical Sciences > School of Mathematics, Statistics and Actuarial Science
Divisions > Division of Natural Sciences > Physics and Astronomy
Depositing User: Dirk Froebrich
Date Deposited: 18 Apr 2018 12:24 UTC
Last Modified: 03 Sep 2021 14:00 UTC
Resource URI: (The current URI for this page, for reference purposes)
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