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The SOFIA Massive (SOMA) star formation Q-band follow-up II. Hydrogen recombination lines towards high-mass protostars

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Název: The SOFIA Massive (SOMA) star formation Q-band follow-up II. Hydrogen recombination lines towards high-mass protostars
Autoři: Gorai, Prasanta, Taniguchi, Kotomi, Tan, Jonathan, 1973, Gomez-Garrido, Miguel, Rosero, Viviana, Jimenez-Serra, Izaskun, Zhang, Yichen, Cosentino, Giuliana, Law, Chi-Yan, Fedriani, Ruben, Busquet, Gemma, Gaches, Brandt A. L., Saberi, Maryam, Das, Ankan
Zdroj: Astronomy and Astrophysics. 702
Témata: stars: massive, line: identification, line: profiles, methods: data analysis, HII regions, astrochemistry
Popis: 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 (H alpha and H beta) 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 H alpha (n = 51 to 58) and ten H beta (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 similar to 1-5 x 10(6) 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 H alpha and H beta 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.
Popis souboru: electronic
Přístupová URL adresa: https://research.chalmers.se/publication/548806
https://research.chalmers.se/publication/548806/file/548806_Fulltext.pdf
Databáze: SwePub
Popis
Abstrakt: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 (H alpha and H beta) 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 H alpha (n = 51 to 58) and ten H beta (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 similar to 1-5 x 10(6) 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 H alpha and H beta 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.
ISSN:00046361
14320746
DOI:10.1051/0004-6361/202556220