The SOFIA Massive (SOMA) star formation Q-band follow-up
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Le résumé fourni par la source
Context. Hydrogen recombination lines (HRLs) are valuable diagnostics of the physical conditions in ionized regions surrounding high-mass stars. Understanding these lines, including broadening mechanisms and intensity trends, can provide insights into HII region densities, temperatures, and kinematics. Aims. This study aims to investigate the physical properties of ionized gas around massive protostars by analysing the HRLs (Hα and Hβ) in the Q band. Methods. We carried out observations using the Yebes 40m radio telescope in the Q band (30.5–50 GHz) towards six high-mass protostars selected from the SOMA Survey (G45.12+0.13, G45.47+0.05, G28.20−0.05, G35.20−0.74, G19.08−0.29, and G31.28+0.06). The observed line profiles were analysed to assess broadening mechanisms, and electron densities and temperatures were derived. The results were compared with available Q-band data from the TianMa 65-m Radio Telescope (TMRT) that have been reported in the literature, and ALMA Band 1 (35–50 GHz) Science Verification observations towards Orion KL, analysed in this study. Results. A total of eight Hα (n = 51 to 58) and ten Hβ (n = 64 to 73) lines were detected towards G45.12+0.13, G45.47+0.05, and G28.20−0.05; there were no detections in other sources. We derived electron densities of ~1−5 × 106 cm−3 and temperatures of 8000–10 000 K for the sources. However, for Orion KL, we obtained an electron density one order of magnitude lower, while its temperature was found to be more similar. Interestingly, G45.12 and G28.20 show an increasing intensity trend with frequency for both Hα and Hβ transitions, contrary to the decreasing trend observed in Orion KL. Conclusions. The line widths of the detected HRLs indicate contributions from both thermal and dynamical broadening, suggesting the presence of high-temperature ionized gas that is likely kinematically broadened (e.g. due to turbulence, outflows, rapid rotation, or stellar winds). Pressure broadening caused by electron density may also have a minor effect. We discuss different scenarios to explain the measured line widths of the HRLs. The contrasting intensity trends between the sources may reflect variations in local physical conditions or radiative transfer effects, highlighting the need for further investigation through higher-resolution observations and detailed modelling.
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Où se fait cette recherche
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University of Oslo Institute of Theoretical Astrophysics pays non établi dans la noticeUniversité ou école supérieure
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National Astronomical Observatory of Japan pays non établi dans la noticeStructure de recherche
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University of Virginia Department of Astronomy pays non établi dans la noticeUniversité ou école supérieure
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Chalmers University of Technology Department of Space pays non établi dans la noticeUniversité ou école supérieure
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Spanish National Observatory pays non établi dans la noticeStructure de recherche
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California Institute of Technology and Astronomy pays non établi dans la noticeUniversité ou école supérieure
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Centro de Astrobiología pays non établi dans la noticeStructure de recherche
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Shanghai Jiao Tong University Department of Astronomy pays non établi dans la noticeUniversité ou école supérieure
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Institut de Radioastronomie Millimétrique pays non établi dans la noticeStructure de recherche
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Arcetri Astrophysical Observatory pays non établi dans la noticeStructure de recherche
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Instituto de Astrofísica de Andalucía pays non établi dans la noticeStructure de recherche
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Catalonian Research and Innovation Centre pays non établi dans la noticeInstitution
Institute of Theoretical Astrophysics — University of Oslo, National Astronomical Observatory of Japan et Department of Astronomy — University of Virginia, avec 9 autres affiliations.
Une affiliation ne permet pas de déduire la nationalité d’un auteur.