{"oa_version":"Published Version","page":"2943-2957","date_updated":"2025-10-27T09:10:22Z","date_published":"2025-09-25T00:00:00Z","publication":"Monthly Notices of the Royal Astronomical Society","publisher":"Oxford University Press","year":"2025","month":"09","publication_identifier":{"eissn":["1365-2966"],"issn":["0035-8711"]},"abstract":[{"lang":"eng","text":"The H i gas distribution in damped Lyman $\\alpha$ absorbers (DLAs) has remained elusive due to the point-source nature of background quasar emission. Observing DLAs against spatially extended background galaxies provides a new method for constraining their size and structure. Using the Keck Cosmic Web Imager, we present the first ‘silhouette’ image of a DLA at $z=3.34$, identified in the spectrum of a background galaxy at $z=3.61$. Although the silhouette remains unresolved due to limited spatial resolution, this represents a successful proof-of-concept for studying DLA morphology using extended background sources. Possible residual emission in the DLA trough suggests an optical depth contrast exceeding $10^7$ in the internal structure, implying a sharp edge or patchy structure. A Lyman $\\alpha$ emitter (LAE) at $z_{\\rm LAE}=3.3433\\pm 0.0005$, consistent with the DLA redshift, is detected at an angular separation of $1{{_{.}^{\\prime\\prime}} }73\\pm 0{{_{.}^{\\prime\\prime}} }28$ ($12.9\\pm 2.1$ kpc). The DLA is surrounded by three galaxies within 140 kpc in projected distance and 500 km s$^{-1}$ in line-of-sight velocity, indicating that it resides in the circumgalactic medium of the LAE or within a galaxy group/protocluster environment. An O i  $\\lambda 1302$ absorption at $z_{\\rm OI}=3.3288\\pm 0.0004$ is also detected along the line of sight. This absorber may trace metal-enriched outflow from the LAE or a gas-rich galaxy exhibiting the highest star formation activity among the surrounding galaxies. Future large spectroscopic surveys of galaxies will expand such a DLA sample, and three-dimensional spectroscopy for it will shed new light on the role of intergalactic dense gas in galaxy formation and evolution."}],"title":"The first direct imaging of the silhouette of a damped Lyman α system along the line-of-sight to a background galaxy","OA_place":"publisher","file":[{"file_size":4864160,"creator":"dernst","file_id":"20549","success":1,"file_name":"2025_MonthlyNoticesRAS_Komori.pdf","access_level":"open_access","date_created":"2025-10-27T09:06:51Z","date_updated":"2025-10-27T09:06:51Z","checksum":"d3190e974ce771e96c4c16ee98abb82a","relation":"main_file","content_type":"application/pdf"}],"license":"https://creativecommons.org/licenses/by/4.0/","citation":{"ama":"Komori F, Inoue AK, Mawatari K, et al. The first direct imaging of the silhouette of a damped Lyman α system along the line-of-sight to a background galaxy. <i>Monthly Notices of the Royal Astronomical Society</i>. 2025;543(3):2943-2957. doi:<a href=\"https://doi.org/10.1093/mnras/staf1622\">10.1093/mnras/staf1622</a>","short":"F. Komori, A.K. Inoue, K. Mawatari, Y. Sugahara, H. Umehata, R. Shimakawa, S. Yamanaka, T. Hashimoto, J.J. Matthee, T. Misawa, Monthly Notices of the Royal Astronomical Society 543 (2025) 2943–2957.","ieee":"F. Komori <i>et al.</i>, “The first direct imaging of the silhouette of a damped Lyman α system along the line-of-sight to a background galaxy,” <i>Monthly Notices of the Royal Astronomical Society</i>, vol. 543, no. 3. Oxford University Press, pp. 2943–2957, 2025.","mla":"Komori, Fuga, et al. “The First Direct Imaging of the Silhouette of a Damped Lyman α System along the Line-of-Sight to a Background Galaxy.” <i>Monthly Notices of the Royal Astronomical Society</i>, vol. 543, no. 3, Oxford University Press, 2025, pp. 2943–57, doi:<a href=\"https://doi.org/10.1093/mnras/staf1622\">10.1093/mnras/staf1622</a>.","ista":"Komori F, Inoue AK, Mawatari K, Sugahara Y, Umehata H, Shimakawa R, Yamanaka S, Hashimoto T, Matthee JJ, Misawa T. 2025. The first direct imaging of the silhouette of a damped Lyman α system along the line-of-sight to a background galaxy. Monthly Notices of the Royal Astronomical Society. 543(3), 2943–2957.","apa":"Komori, F., Inoue, A. K., Mawatari, K., Sugahara, Y., Umehata, H., Shimakawa, R., … Misawa, T. (2025). The first direct imaging of the silhouette of a damped Lyman α system along the line-of-sight to a background galaxy. <i>Monthly Notices of the Royal Astronomical Society</i>. Oxford University Press. <a href=\"https://doi.org/10.1093/mnras/staf1622\">https://doi.org/10.1093/mnras/staf1622</a>","chicago":"Komori, Fuga, Akio K Inoue, Ken Mawatari, Yuma Sugahara, Hideki Umehata, Rhythm Shimakawa, Satoshi Yamanaka, Takuya Hashimoto, Jorryt J Matthee, and Toru Misawa. “The First Direct Imaging of the Silhouette of a Damped Lyman α System along the Line-of-Sight to a Background Galaxy.” <i>Monthly Notices of the Royal Astronomical Society</i>. Oxford University Press, 2025. <a href=\"https://doi.org/10.1093/mnras/staf1622\">https://doi.org/10.1093/mnras/staf1622</a>."},"user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","oa":1,"day":"25","tmp":{"legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","short":"CC BY (4.0)","image":"/images/cc_by.png","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)"},"article_processing_charge":"Yes","intvolume":"       543","department":[{"_id":"JoMa"}],"publication_status":"published","issue":"3","doi":"10.1093/mnras/staf1622","OA_type":"gold","language":[{"iso":"eng"}],"volume":543,"author":[{"full_name":"Komori, Fuga","last_name":"Komori","first_name":"Fuga"},{"first_name":"Akio K","last_name":"Inoue","full_name":"Inoue, Akio K"},{"first_name":"Ken","last_name":"Mawatari","full_name":"Mawatari, Ken"},{"full_name":"Sugahara, Yuma","last_name":"Sugahara","first_name":"Yuma"},{"last_name":"Umehata","full_name":"Umehata, Hideki","first_name":"Hideki"},{"first_name":"Rhythm","last_name":"Shimakawa","full_name":"Shimakawa, Rhythm"},{"first_name":"Satoshi","full_name":"Yamanaka, Satoshi","last_name":"Yamanaka"},{"first_name":"Takuya","full_name":"Hashimoto, Takuya","last_name":"Hashimoto"},{"first_name":"Jorryt J","id":"7439a258-f3c0-11ec-9501-9df22fe06720","full_name":"Matthee, Jorryt J","last_name":"Matthee","orcid":"0000-0003-2871-127X"},{"last_name":"Misawa","full_name":"Misawa, Toru","first_name":"Toru"}],"DOAJ_listed":"1","ddc":["520"],"_id":"20545","date_created":"2025-10-27T08:18:07Z","quality_controlled":"1","PlanS_conform":"1","type":"journal_article","file_date_updated":"2025-10-27T09:06:51Z","article_type":"original","acknowledgement":"We thank Seiji Fujimoto for discussions in the early stage of this work. We were supported by JSPS (Japan Society for the Promotion of Science) KAKENHI Grant Numbers 21H04489, 22H04939, 23H00131, 24H00002, 24K17095, 25K01038, and 25K01039. Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c)3 non-profit organization operated as a scientific partnership among the California Institute of Technology,\r\nthe University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the Native Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this\r\nmountain. This research made use of MONTAGE. It is funded by the National Science Foundation under Grant Number ACI-1440620, and was previously funded by the National Aeronautics and Space Administration’s Earth Science Technology Office, Computation\r\nTechnologies Project, underCooperative Agreement Number NCC5-626 between NASA and the California Institute of Technology.","status":"public","scopus_import":"1","has_accepted_license":"1"}