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| Main Authors: | , , , , , , , , , , , , , , , , , , |
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| Format: | Preprint |
| Published: |
2025
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2505.04212 |
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| _version_ | 1866916949450031104 |
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| author | Zhou, Hang Wang, Xin Malkan, Matthew A. Treu, Tommaso Yang, Yiming Cai, Zheng Fan, Xiaohui Ju, Mengting Shi, Dong Dong Alavi, Anahita Bian, Fuyan Colbert, James Henry, Alaina L. Li, Sijia Li, Zihao Teplitz, Harry I. Zhan, Hu Zheng, Xian Zhong Zheng, Zheng |
| author_facet | Zhou, Hang Wang, Xin Malkan, Matthew A. Treu, Tommaso Yang, Yiming Cai, Zheng Fan, Xiaohui Ju, Mengting Shi, Dong Dong Alavi, Anahita Bian, Fuyan Colbert, James Henry, Alaina L. Li, Sijia Li, Zihao Teplitz, Harry I. Zhan, Hu Zheng, Xian Zhong Zheng, Zheng |
| contents | The MAMMOTH-MOSFIRE program is a deep Keck/MOSFIRE K-band spectroscopic follow-up of emission-line galaxies identified in the MAMMOTH-Grism HST/WFC3 G141 slitless spectroscopic survey, targeting the core regions of three most massive galaxy protoclusters at cosmic noon. To introduce this program, we present a comprehensive analysis of the $\rm [N\,II]λ$6584, $\rm [S\,II]λλ$6717,6731, and $\rm [O\,I]λ$6300 BPT diagnostics for a unique sample of 43 protocluster member galaxies at $z\sim2$, investigating how the overdense environment influences their interstellar medium ionization conditions. We find that, similar to their field counterparts at $z\sim2$, protocluster galaxies exhibit a systematic offset in the $\rm [N\,II]$ BPT diagram relative to the local star-forming sequence, but no such offset in the $\rm [S\,II]$ BPT diagram. Notably, we detect significantly elevated $\rm [O\,I]$/$\rm H α$ ratios, which can be well reproduced by photoionization models incorporating both $\rm H II$ regions and low-velocity shocks ($v$ $\sim$ 200 km s$^{-1}$). We caution that neglecting shock excitation can bias abundance measurements, leading to an overestimation of nitrogen enrichment. This provides a potential explanation for the long-standing puzzle of enhanced $\rm [N\,II]$/$\rm H α$ ratios observed in $z\sim2$ galaxies. We further suggest that these shocks are likely environmentally driven, e.g., by ram-pressure stripping or tidal interactions, which requires future confirmation through direct observations of features such as stripped gas tails. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2505_04212 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | MAMMOTH-MOSFIRE: Environmental Effects on Galaxy Interstellar Medium at $z\sim2$ Zhou, Hang Wang, Xin Malkan, Matthew A. Treu, Tommaso Yang, Yiming Cai, Zheng Fan, Xiaohui Ju, Mengting Shi, Dong Dong Alavi, Anahita Bian, Fuyan Colbert, James Henry, Alaina L. Li, Sijia Li, Zihao Teplitz, Harry I. Zhan, Hu Zheng, Xian Zhong Zheng, Zheng Astrophysics of Galaxies The MAMMOTH-MOSFIRE program is a deep Keck/MOSFIRE K-band spectroscopic follow-up of emission-line galaxies identified in the MAMMOTH-Grism HST/WFC3 G141 slitless spectroscopic survey, targeting the core regions of three most massive galaxy protoclusters at cosmic noon. To introduce this program, we present a comprehensive analysis of the $\rm [N\,II]λ$6584, $\rm [S\,II]λλ$6717,6731, and $\rm [O\,I]λ$6300 BPT diagnostics for a unique sample of 43 protocluster member galaxies at $z\sim2$, investigating how the overdense environment influences their interstellar medium ionization conditions. We find that, similar to their field counterparts at $z\sim2$, protocluster galaxies exhibit a systematic offset in the $\rm [N\,II]$ BPT diagram relative to the local star-forming sequence, but no such offset in the $\rm [S\,II]$ BPT diagram. Notably, we detect significantly elevated $\rm [O\,I]$/$\rm H α$ ratios, which can be well reproduced by photoionization models incorporating both $\rm H II$ regions and low-velocity shocks ($v$ $\sim$ 200 km s$^{-1}$). We caution that neglecting shock excitation can bias abundance measurements, leading to an overestimation of nitrogen enrichment. This provides a potential explanation for the long-standing puzzle of enhanced $\rm [N\,II]$/$\rm H α$ ratios observed in $z\sim2$ galaxies. We further suggest that these shocks are likely environmentally driven, e.g., by ram-pressure stripping or tidal interactions, which requires future confirmation through direct observations of features such as stripped gas tails. |
| title | MAMMOTH-MOSFIRE: Environmental Effects on Galaxy Interstellar Medium at $z\sim2$ |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2505.04212 |