MAMMOTH-Grism: Revisiting the Mass–Metallicity Relation in Protocluster Environments at Cosmic Noon
Year: 2026
Type: article
Abstract: We present one of the first measurements of the mass–metallicity relation (MZR) in multiple massive protoclusters at cosmic noon, using Hubble Space Telescope (HST) G141 slitless spectroscopy from the MAMMOTH-Grism survey. We identify 63 protocluster member galaxies across three overdense structures at z = 2–3 with robust detections of [O iii ], H β , and [O ii ] emission. The sample spans gas-phase metallicities of 12 + log ( O / H ) = 8.2 − 8.6 , dust-corrected H β -based star formation rates (SFRs) of 10–250 M ⊙ yr −1 , and stellar masses of M * ∼ 10 9.4 –10 10.5 M ⊙ , derived via spectral energy distribution fitting using deep HST and ground-based photometry. We stack spectra in five M * bins to obtain average metallicities and SFRs. Relative to field galaxies at similar redshifts, protocluster members show elevated SFRs at M * < 10 10.25 M ⊙ and a systematically shallower MZR: 12 + log ( O / H ) =(6.96 ± 0.13) + (0.143 ± 0.017) × log ( M * / M ⊙ ) . We detect a mass-dependent environmental offset: massive protocluster galaxies are metal-poor compared to field counterparts of similar mass, whereas lower-mass systems exhibit comparable or mildly enhanced metallicities. This trend is consistent with a scenario where cold-mode accretion dilutes the interstellar medium (ISM) across the full mass range, while efficient recycling of feedback-driven outflows preferentially enriches the ISM in low-mass galaxies. Finally, we assess the dependence of metallicity offsets on local overdensity and find no significant trend, likely reflecting the survey’s bias toward protocluster cores.
Source: The Astrophysical Journal
Authors: Yiming Yang, Xin Wang, Xianlong He, Chao-Wei Tsai, Zheng Cai, Zihao Li, Matthew A. Malkan, Dong Dong Shi, Anahita Alavi, Fuyan Bian, James Colbert, Xiaohui Fan, Alaina L. Henry, Harry I. Teplitz, Xian Zhong Zheng
Institutions: Chinese Academy of Sciences, National Astronomical Observatories, University of Chinese Academy of Sciences, Beijing Normal University, University of California, Los Angeles, Wuhan University, Tsinghua University, University of Copenhagen, Anhui University of Science and Technology, California Institute of Technology, Infrared Processing and Analysis Center, European Southern Observatory, University of Arizona, Space Telescope Science Institute, Shanghai Jiao Tong University
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Funders: National Science Foundation, National Aeronautics and Space Administration, Space Telescope Science Institute, Swinburne University of Technology, National Natural Science Foundation of China, Government of Jiangsu Province, Office of Science, National Key Research and Development Program of China, Fundamental Research Funds for the Central Universities
OpenAlex ID: W7113895924