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| Main Authors: | , , , , , , |
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| Format: | Preprint |
| Published: |
2026
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2605.09412 |
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| _version_ | 1866913108029603840 |
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| author | Rodríguez-Esnard, I. T. Kurtz, S. Pandian, J. D. Franco, J. Sánchez-Monge, A. Trinidad, M. A. Migenes, V. |
| author_facet | Rodríguez-Esnard, I. T. Kurtz, S. Pandian, J. D. Franco, J. Sánchez-Monge, A. Trinidad, M. A. Migenes, V. |
| contents | Hypercompact HII regions (HC) are regions of ionized gas associated with the early stages of high-mass star formation. With the aim of better understanding their characteristics, we studied five candidate HC HII regions. Here, we present observations with the Jansky Very Large Array (VLA) at 2 and 6 cm, with angular resolutions in the range of $\sim$1 -- 3\arcsec and report the images of the detected sources and the measured parameters. In addition, we explore several possible scenarios, considering the regions as both uniform and non-uniform spheres, and as winds, both spherical and collimated. In most cases, the sources were unresolved, but by applying the models, we estimate that their sizes vary in a range of 0.3 to 3.7 mpc while their electron densities are in the range of $1.3 \times 10^{5}$ to $2.4 \times 10^{6}$ cm$^{-3}$, indicating that most sources are consistent with small, weak UC HII regions, although a few remain viable candidates for HC HII regions, with G40.28$-$0.22 as the strongest case. We do not rule out the possibility that some sources are jets or stellar winds. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_09412 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Physical characterization and modeling of candidate Hyper-Compact HII Regions Rodríguez-Esnard, I. T. Kurtz, S. Pandian, J. D. Franco, J. Sánchez-Monge, A. Trinidad, M. A. Migenes, V. Astrophysics of Galaxies Solar and Stellar Astrophysics Hypercompact HII regions (HC) are regions of ionized gas associated with the early stages of high-mass star formation. With the aim of better understanding their characteristics, we studied five candidate HC HII regions. Here, we present observations with the Jansky Very Large Array (VLA) at 2 and 6 cm, with angular resolutions in the range of $\sim$1 -- 3\arcsec and report the images of the detected sources and the measured parameters. In addition, we explore several possible scenarios, considering the regions as both uniform and non-uniform spheres, and as winds, both spherical and collimated. In most cases, the sources were unresolved, but by applying the models, we estimate that their sizes vary in a range of 0.3 to 3.7 mpc while their electron densities are in the range of $1.3 \times 10^{5}$ to $2.4 \times 10^{6}$ cm$^{-3}$, indicating that most sources are consistent with small, weak UC HII regions, although a few remain viable candidates for HC HII regions, with G40.28$-$0.22 as the strongest case. We do not rule out the possibility that some sources are jets or stellar winds. |
| title | Physical characterization and modeling of candidate Hyper-Compact HII Regions |
| topic | Astrophysics of Galaxies Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2605.09412 |