Patel, A. L., Urquhart, J.S., Yang, A.Y., Moore, T., Thompson, M.A., Menten, K.M., Csengeri, T. (2024) SCOTCH − Search for Clandestine Optically Thick Compact H ii regions: II. Monthly Notices of the Royal Astronomical Society, . Article Number stae1910. ISSN 0035-8711. (doi:10.1093/mnras/stae1910) (KAR id:106831)
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Official URL: https://doi.org/10.1093/mnras%2Fstae1910 |
Abstract
In this study we present 18-24 GHz and high-angular-resolution (0.5 arcsec) radio wavelength Australia Telescope Compact Array (ATCA) follow-up observations towards a sample of 39 HC H ii region candidates. These objects, taken from a sample hosting 6.7 GHz methanol masers, were chosen due to the compact and optically thick nature of their continuum emission. We have detected 27 compact radio sources and constructed their spectral energy distributions (SEDs) over the 5–24 GHz range to determine the young H ii region’s physical properties, i.e., diameter, electron density ne, emission measure, Lyman continuum flux NLy and turnover frequency νt. The flux measurements are fitted for 20 objects assuming an ionisation-bounded H ii region with uniform density model. For the remaining 7 objects that lack constraints spanning both their optically thick and thin regimes, we utilise relations from the literature to determine their physical properties. Comparing these determined parameters with those of known hypercompact (HC) and ultracompact (UC) H ii regions, we have identified 13 HC H ii regions, 6 intermediate objects that fall between HC H ii and UC H ii regions, 6 UC H ii regions and one radio jet candidate which increases the known population of HC H ii regions by ∼50 per cent. All the young and compact H ii regions are embedded in dusty and dense clumps and ∼80 per cent of the HC H ii regions identified in this work are associated with various maser species (CH3OH, H2O and OH). Four of our radio sources remain optically thick at 24 GHz; we consider these to be amongst the youngest HC H ii regions.
Item Type: | Article |
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DOI/Identification number: | 10.1093/mnras/stae1910 |
Uncontrolled keywords: | stars: evolution, stars: formation, (ISM:) HII regions, radio continuum: stars |
Subjects: | Q Science > QB Astronomy > QB460 Astrophysics |
Divisions: | Divisions > Division of Natural Sciences > Physics and Astronomy |
Funders: |
Science and Technology Facilities Council (https://ror.org/057g20z61)
National Natural Science Foundation of China (https://ror.org/01h0zpd94) |
Depositing User: | James Urquhart |
Date Deposited: | 09 Aug 2024 08:39 UTC |
Last Modified: | 09 Aug 2024 10:17 UTC |
Resource URI: | https://kar.kent.ac.uk/id/eprint/106831 (The current URI for this page, for reference purposes) |
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