AGNs in the Extremely Overdense Galaxy Region BOSS~1441: A Chandra Observation
AGNs in the Extremely Overdense Galaxy Region BOSS~1441: A Chandra Observation
Jiahua Wu 1Liming Dou 1Zheng Cai 2Yanli Ai Shiwu Zhang Zhenya Zheng Xiaohui Fan Yuanyuan Su Jianfeng Wu
作者信息
- 1. Guangzhou University
- 2. Tsinghua University
- 折叠
摘要
We present a Chandra/ACIS-I study of X-ray sources in BOSS~1441, a protocluster at $z=2.32\pm0.02$ that exhibits a prominent overdensity of Ly$\alpha$ emitters (LAEs).Using a 45\,ks observation, we identify seven X-ray sources spatially coincident with LAE density peaks. The average X-ray photon index for the seven sources, derived from an absorbed power-law model with Galactic absorption fixed, is 1.49 (ranging from -0.68 to 2.51), corresponding to an average luminosity of 6.85$\rm\times 10^{44}~erg~s^{-1}$ in the rest-frame 2-33 keV band, with individual luminosities spanning (3.57--13.96)$\rm\times 10^{44}~erg~s^{-1}$. Three sources exhibit relatively flat spectral slopes. Two are associated with the MAMMOTH-1 nebula, while the third, located at the edge of BOSS 1441 with a $>\,5\arcmin$ offset from the LAE density peak, resides in a region with a high submillimeter-band density. We estimate the fraction of X-ray detected AGNs among the LAEs to be $11.5^{+3.8}_{-4.6}\%$, approximately double that of previously studied LAEs. This elevated fraction suggests BOSS 1441 is in a mature evolutionary stage, with even higher AGN fractions expected in massive LAEs such as PKS~1138-262. In contrast, the submillimeter galaxy population shows a lower AGN fraction ($6.9^{+6.9}_{-4.5}\%$), consistent with their typically obscured nature.These results indicate that the protocluster’s massive galaxies are evolving into the bright red sequence galaxies observed in local clusters, where AGNs likely play a critical role in quenching their star formation.
Abstract
We present a Chandra/ACIS-I study of X-ray sources in BOSS~1441, a protocluster at $z=2.32\pm0.02$ that exhibits a prominent overdensity of Ly$\alpha$ emitters (LAEs).Using a 45\,ks observation, we identify seven X-ray sources spatially coincident with LAE density peaks. The average X-ray photon index for the seven sources, derived from an absorbed power-law model with Galactic absorption fixed, is 1.49 (ranging from -0.68 to 2.51), corresponding to an average luminosity of 6.85$\rm\times 10^{44}~erg~s^{-1}$ in the rest-frame 2-33 keV band, with individual luminosities spanning (3.57--13.96)$\rm\times 10^{44}~erg~s^{-1}$. Three sources exhibit relatively flat spectral slopes. Two are associated with the MAMMOTH-1 nebula, while the third, located at the edge of BOSS 1441 with a $>\,5\arcmin$ offset from the LAE density peak, resides in a region with a high submillimeter-band density. We estimate the fraction of X-ray detected AGNs among the LAEs to be $11.5^{+3.8}_{-4.6}\%$, approximately double that of previously studied LAEs. This elevated fraction suggests BOSS 1441 is in a mature evolutionary stage, with even higher AGN fractions expected in massive LAEs such as PKS~1138-262. In contrast, the submillimeter galaxy population shows a lower AGN fraction ($6.9^{+6.9}_{-4.5}\%$), consistent with their typically obscured nature.These results indicate that the protoclusters massive galaxies are evolving into the bright red sequence galaxies observed in local clusters, where AGNs likely play a critical role in quenching their star formation.关键词
Protoclusters/X-ray active galactic nuclei/Lyman-alpha galaxiesKey words
Protoclusters/X-ray active galactic nuclei/Lyman-alpha galaxies引用本文复制引用
Jiahua Wu,Liming Dou,Zheng Cai,Yanli Ai,Shiwu Zhang,Zhenya Zheng,Xiaohui Fan,Yuanyuan Su,Jianfeng Wu.AGNs in the Extremely Overdense Galaxy Region BOSS~1441: A Chandra Observation[EB/OL].(2025-12-09)[2026-04-06].https://chinaxiv.org/abs/202512.00068.学科分类
天文学
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