New insights into the role of AGNs in forming the cluster red sequence

Shimakawa, Rhythm; Pérez-Martínez, Jose Manuel; Koyama, Yusei; Tanaka, Masayuki; Tanaka, Ichi; Kodama, Tadayuki; Hatch, Nina A.; Röttgering, Huub J.A.; Dannerbauer, Helmut; Kurk, Jaron D.

Abstract

As a considerable investment of time from various telescope facilities was dedicated toward studying the Spiderweb protocluster at z = 2.2, it so far remains one of the most extensively studied protocluster. We report here the latest results in this field, adding a new dimension to previous research on cluster formation at high redshift. Previous studies have reported a significant overdensity (δ ∼ 10) of massive Hα (+ [N ii])-emitting galaxies in 3700 comoving Mpc3. Many of these were previously considered to be dusty, actively star-forming galaxies, given their rest-frame optical and infrared features. However, this study argues that a third of them are more likely to be ‘passively evolving’ galaxies with low-luminosity active galactic nuclei (AGNs) rather than star-forming galaxies, given the multiwavelength spectral energy distribution (SED) fitting including an AGN component. For their SED-based star formation rates to be valid, bulk of their Hα + [N ii] emission should come from the central AGNs. This difference in interpretation between this work and past studies, including ours, is particularly supported by the recent deep Chandra/X-ray observation. Furthermore, we have spectroscopically confirmed a quiescent nature for one of these AGNs, with its multiple stellar absorption lines but also low-ionization emission lines. This important update provides new insights into the role of AGNs in forming the cluster red sequence observed in the present-day universe.

Citation

Shimakawa, R., Pérez-Martínez, J. M., Koyama, Y., Tanaka, M., Tanaka, I., Kodama, T., Hatch, N. A., Röttgering, H. J., Dannerbauer, H., & Kurk, J. D. (2024). New insights into the role of AGNs in forming the cluster red sequence. Monthly Notices of the Royal Astronomical Society, 528(2), 3679–3695. https://doi.org/10.1093/mnras/stae118

• Journal Article Type: Article
• Acceptance Date: Jan 10, 2024
• Online Publication Date: Jan 11, 2024
• Publication Date: 2024-02
• Deposit Date: Mar 17, 2024
• Publicly Available Date: Mar 17, 2024
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 528
• Issue: 2
• Pages: 3679–3695
• DOI: https://doi.org/10.1093/mnras/stae118
• Keywords: galaxies: clusters: individual: PKS 1138−262, galaxies: evolution, galaxies: formation, galaxies: high-redshift
• Public URL: https://nottingham-repository.worktribe.com/output/29842273
• Publisher URL: https://academic.oup.com/mnras/article/528/2/3679/7517094