Spatially-resolved Galactic HII regions observed by LAMOST medium-Resolution Spectroscopic Survey of Nebulae (LAMOST MRS-N)
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| Autori principali: | , , , , , , , , , , , |
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| Natura: | Preprint |
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2025
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| _version_ | 1866915239519322112 |
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| author | Zhang, Wei Zhao, Yunning Ma, Lin Wen, Shiming Wu, Chaojian Ren, Juanjuan Chen, Jianjun Wu, Yuzhong Bai, Zhongrui Hou, Yonghui Zhao, Yongheng Wu, Hong |
| author_facet | Zhang, Wei Zhao, Yunning Ma, Lin Wen, Shiming Wu, Chaojian Ren, Juanjuan Chen, Jianjun Wu, Yuzhong Bai, Zhongrui Hou, Yonghui Zhao, Yongheng Wu, Hong |
| contents | We present spatially-resolved spectroscopic observations of 10 isolated Galactic HII regions using data from the LAMOST Medium-Resolution Spectroscopic Survey of Nebulae (LAMOST MRS-N). The high spatial resolution of the data allows us to investigate the 1D radial profiles of emission line fluxes (Ha, [S II] and [N II]), flux ratios ([N II]/Ha, [S II]/Ha and [S II]/[N II]), and radial velocities of these three emission lines. Among these regions, two are ionization-bounded, while the remaining eight are matter-bounded. The matter-bounded HII regions exhibit shallower slopes in their radial flux profiles compared to the ionization-bounded ones. In most cases, the [N II]/Ha and [S II]/Ha ratios increase with distance from the center of the HII regions, consistent with model predictions that low-ionization emissions dominate the outer zones of these regions. The two ionization-bounded HII regions have kinematic ages (t) of 0.2 and 0.3 Myr, while the matter-bounded regions span ages from 1 to 12 Myr. For the matter-bounded HII regions, the optical emission flux decreases continuously beyond the photodissociation region (PDR), extending to approximately 1-4 times the radius of the PDR (r_PDR). The escape fraction f_esc of ionizing photons, derived from 1D Ha radial flux profiles, is ~ 0% for ionization-bounded HII regions, while it ranges from 50% to 90% for the matter-bounded HII regions. The correlation between f_esc and t suggests that evolved HII regions (with t > 1 Myr) contribute more significantly to ionizing the surrounding diffuse ionized gas compared to younger, newly formed HII regions. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2503_07954 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Spatially-resolved Galactic HII regions observed by LAMOST medium-Resolution Spectroscopic Survey of Nebulae (LAMOST MRS-N) Zhang, Wei Zhao, Yunning Ma, Lin Wen, Shiming Wu, Chaojian Ren, Juanjuan Chen, Jianjun Wu, Yuzhong Bai, Zhongrui Hou, Yonghui Zhao, Yongheng Wu, Hong Astrophysics of Galaxies We present spatially-resolved spectroscopic observations of 10 isolated Galactic HII regions using data from the LAMOST Medium-Resolution Spectroscopic Survey of Nebulae (LAMOST MRS-N). The high spatial resolution of the data allows us to investigate the 1D radial profiles of emission line fluxes (Ha, [S II] and [N II]), flux ratios ([N II]/Ha, [S II]/Ha and [S II]/[N II]), and radial velocities of these three emission lines. Among these regions, two are ionization-bounded, while the remaining eight are matter-bounded. The matter-bounded HII regions exhibit shallower slopes in their radial flux profiles compared to the ionization-bounded ones. In most cases, the [N II]/Ha and [S II]/Ha ratios increase with distance from the center of the HII regions, consistent with model predictions that low-ionization emissions dominate the outer zones of these regions. The two ionization-bounded HII regions have kinematic ages (t) of 0.2 and 0.3 Myr, while the matter-bounded regions span ages from 1 to 12 Myr. For the matter-bounded HII regions, the optical emission flux decreases continuously beyond the photodissociation region (PDR), extending to approximately 1-4 times the radius of the PDR (r_PDR). The escape fraction f_esc of ionizing photons, derived from 1D Ha radial flux profiles, is ~ 0% for ionization-bounded HII regions, while it ranges from 50% to 90% for the matter-bounded HII regions. The correlation between f_esc and t suggests that evolved HII regions (with t > 1 Myr) contribute more significantly to ionizing the surrounding diffuse ionized gas compared to younger, newly formed HII regions. |
| title | Spatially-resolved Galactic HII regions observed by LAMOST medium-Resolution Spectroscopic Survey of Nebulae (LAMOST MRS-N) |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2503.07954 |