Diffuse Ionized Gas in the Anti-center of the Milky Way
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| Main Authors: | , , , , , , , , , , , , |
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| Format: | Preprint |
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2024
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| _version_ | 1866910811661795328 |
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| author | Wen, Shiming Zhang, Wei Ma, Lin Zhao, Yunning Lam, Man I. Wu, Chaojian Ren, Juanjuan Chen, Jianjun Wu, Yuzhong Hu, Guozhen Hou, Yonghui Zhao, Yongheng Wu, Hong |
| author_facet | Wen, Shiming Zhang, Wei Ma, Lin Zhao, Yunning Lam, Man I. Wu, Chaojian Ren, Juanjuan Chen, Jianjun Wu, Yuzhong Hu, Guozhen Hou, Yonghui Zhao, Yongheng Wu, Hong |
| contents | Using data from the LAMOST Medium-Resolution Spectroscopic Survey of Nebulae, we create a sample of 17,821 diffuse ionized gas (DIG) spectra in the anti-center region of the Milky Way, by excluding fibers in the directions of H II regions and supernova remnants. We then analyze the radial and vertical distributions of three line ratios ([N II]/H$α$, [S II]/H$α$, and [S II]/[N II]), as well as the oxygen abundance.
[N II]/H$α$ and [S II]/H$α$ do not exhibit a consistent, monotonic decrease with increasing Galactocentric distance (R$_{gal}$). Instead, they show enhancement within the interarm region, positioned between the Local Arm and the Perseus Arm. [S II]/[N II] has a radial gradient of 0.1415 $\pm$ 0.0646 kpc$^{-1}$ for the inner disk (8.34 $ < R_{gal} < $ 9.65 kpc), and remains nearly flat for the outer disk ($R_{gal} > $ 9.65 kpc). In the vertical direction, [N II]/H$α$, [S II]/H$α$, and [S II]/[N II] increase with increasing Galactic disk height ($|z|$) in both southern and northern disks.
Based on the N2S2H$α$ method, which combines [S II]/[N II] and [N II]/H$α$, we estimate the oxygen abundance. The oxygen abundance exhibits a consistent radial gradient with R$_{gal}$, featuring a slope of -0.0559 $\pm$ 0.0209 dex kpc$^{-1}$ for the inner disk and a similar slope of -0.0429 $\pm$ 0.0599 dex kpc$^{-1}$ for the outer disk. A single linear fitting to the entire disk yields a slope of -0.0317 $\pm$ 0.0124 dex kpc$^{-1}$. In the vertical direction, the oxygen abundance decreases with increasing $|z|$ in both southern and northern disks. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2412_05692 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Diffuse Ionized Gas in the Anti-center of the Milky Way Wen, Shiming Zhang, Wei Ma, Lin Zhao, Yunning Lam, Man I. Wu, Chaojian Ren, Juanjuan Chen, Jianjun Wu, Yuzhong Hu, Guozhen Hou, Yonghui Zhao, Yongheng Wu, Hong Astrophysics of Galaxies Using data from the LAMOST Medium-Resolution Spectroscopic Survey of Nebulae, we create a sample of 17,821 diffuse ionized gas (DIG) spectra in the anti-center region of the Milky Way, by excluding fibers in the directions of H II regions and supernova remnants. We then analyze the radial and vertical distributions of three line ratios ([N II]/H$α$, [S II]/H$α$, and [S II]/[N II]), as well as the oxygen abundance. [N II]/H$α$ and [S II]/H$α$ do not exhibit a consistent, monotonic decrease with increasing Galactocentric distance (R$_{gal}$). Instead, they show enhancement within the interarm region, positioned between the Local Arm and the Perseus Arm. [S II]/[N II] has a radial gradient of 0.1415 $\pm$ 0.0646 kpc$^{-1}$ for the inner disk (8.34 $ < R_{gal} < $ 9.65 kpc), and remains nearly flat for the outer disk ($R_{gal} > $ 9.65 kpc). In the vertical direction, [N II]/H$α$, [S II]/H$α$, and [S II]/[N II] increase with increasing Galactic disk height ($|z|$) in both southern and northern disks. Based on the N2S2H$α$ method, which combines [S II]/[N II] and [N II]/H$α$, we estimate the oxygen abundance. The oxygen abundance exhibits a consistent radial gradient with R$_{gal}$, featuring a slope of -0.0559 $\pm$ 0.0209 dex kpc$^{-1}$ for the inner disk and a similar slope of -0.0429 $\pm$ 0.0599 dex kpc$^{-1}$ for the outer disk. A single linear fitting to the entire disk yields a slope of -0.0317 $\pm$ 0.0124 dex kpc$^{-1}$. In the vertical direction, the oxygen abundance decreases with increasing $|z|$ in both southern and northern disks. |
| title | Diffuse Ionized Gas in the Anti-center of the Milky Way |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2412.05692 |