Cosmic Himalayas: The Highest Quasar Density Peak Identified in a 10,000 deg<sup>2</sup> Sky with Spatial Discrepancies between Galaxies, Quasars, and IGM H<scp> i</scp>

Abstract We report the identification of a quasar overdensity in the BOSSJ0210 field, dubbed the Cosmic Himalayas, consisting of 11 quasars at z = 2.16−2.20, the densest overdensity of quasars (17 σ ) in the ∼10,000 deg 2 of the Sloan Digital Sky Survey (SDSS). We present the spatial distributions of galaxies and quasars and a H i absorption map of the intergalactic medium (IGM). On the map of 465 galaxies selected from the MAMMOTH-Subaru survey, we find two galaxy density peaks that do not fall on the quasar overdensity but instead exist at the northwest and southeast sides, approximately 25 h −1 comoving Mpc (cMpc) apart from the quasar overdensity. With a spatial resolution of 15 h −1 cMpc in projection, we produce a three-dimensional H i tomography map by the IGM Ly α forest in the spectra of 23 SDSS/eBOSS quasars behind the quasar overdensity. Surprisingly, the quasar overdensity coincides with neither an absorption peak nor a transmission peak of IGM H i but lies near the border separating opaque and transparent volumes, with the more luminous quasars located in an environment with less IGM H i . Hence, remarkably, the overdensity region traced by the 11 quasars, albeit all in coherently active states, has no clear coincidence with peaks of galaxies or H i absorption densities. Current physical scenarios with mixtures of H i overdensities and quasar photoionization cannot fully interpret the emergence of the Cosmic Himalayas, suggesting this peculiar structure is an excellent laboratory to unveil the interplay between galaxies, quasars, and the IGM.

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Journal
The Astrophysical Journal
Published
2025-06-06
DOI
https://doi.org/10.3847/1538-4357/adc1bb
Citations
1
Primary Topic
Galaxies: Formation, Evolution, Phenomena
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article
Field-Weighted Citation Impact
1.15
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article

Cosmic Himalayas: The Highest Quasar Density Peak Identified in a 10,000 deg2 Sky with Spatial Discrepancies between Galaxies, Quasars, and IGM H i

Takuma Izumi, M. Elvis, A. Travascio, Masafusa Onoue et al.
1 citations
The Astrophysical Journal
Galaxies: Formation, Evolution, Phenomena
1.15
article

Cosmic Himalayas: The Highest Quasar Density Peak Identified in a 10,000 deg2 Sky with Spatial Discrepancies between Galaxies, Quasars, and IGM H i

Takuma Izumi, M. Elvis, A. Travascio, Masafusa Onoue, Nobunari Kashikawa, Hidenobu Yajima, J. D. Silverman, Rhythm Shimakawa, Xiaohui Fan, Jason Xavier Prochaska, Takanobu Kirihara, Hisakazu Uchiyama, Masami Ouchi, Yuichi Harikane, Kazuhiro Shimasaku, Masayuki Tanaka, Yongming Liang, Kentaro Nagamine, Fangxia An, Sebastiano Cantalupo, Zheng Cai, Dong Shi, G. Fabbiano, Kei Ito, Junya Arita, Mingyu Li, Haibin Zhang, Weichen Wang, Dongsheng Sun, Chenghao Zhu
article en
1 citations

Abstract

Abstract We report the identification of a quasar overdensity in the BOSSJ0210 field, dubbed the Cosmic Himalayas, consisting of 11 quasars at z = 2.16−2.20, the densest overdensity of quasars (17 σ ) in the ∼10,000 deg 2 of the Sloan Digital Sky Survey (SDSS). We present the spatial distributions of galaxies and quasars and a H i absorption map of the intergalactic medium (IGM). On the map of 465 galaxies selected from the MAMMOTH-Subaru survey, we find two galaxy density peaks that do not fall on the quasar overdensity but instead exist at the northwest and southeast sides, approximately 25 h −1 comoving Mpc (cMpc) apart from the quasar overdensity. With a spatial resolution of 15 h −1 cMpc in projection, we produce a three-dimensional H i tomography map by the IGM Ly α forest in the spectra of 23 SDSS/eBOSS quasars behind the quasar overdensity. Surprisingly, the quasar overdensity coincides with neither an absorption peak nor a transmission peak of IGM H i but lies near the border separating opaque and transparent volumes, with the more luminous quasars located in an environment with less IGM H i . Hence, remarkably, the overdensity region traced by the 11 quasars, albeit all in coherently active states, has no clear coincidence with peaks of galaxies or H i absorption densities. Current physical scenarios with mixtures of H i overdensities and quasar photoionization cannot fully interpret the emergence of the Cosmic Himalayas, suggesting this peculiar structure is an excellent laboratory to unveil the interplay between galaxies, quasars, and the IGM.

The Astrophysical JournalVol. 986(1)
University of Nevada, Las Vegas (US), University of Arizona (US), University of Tsukuba (JP), Waseda University (JP), Kavli Institute for the Physics and Mathematics of the Universe (JP), University of California, Santa Cruz (US), Chinese Academy of Sciences (CN), The Graduate University for Advanced Studies, SOKENDAI (JP), Purple Mountain Observatory (CN), Toneyama National Hospital (JP), Center for Astrophysics Harvard & Smithsonian (US), National Astronomical Observatory of Japan (JP), University of Milano-Bicocca (IT), The University of Tokyo (JP), Kitami Institute of Technology (JP), Tsinghua University (CN)
Openalex Percentile: Top 19%
Galaxies: Formation, Evolution, Phenomena
1.15
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