Gas filaments of the cosmic web located around active galaxies in a protocluster

Creators: Umehata, H.; Fumagalli, M.; Smail, I.; Matsuda, Y.; Swinbank, A. M.; Cantalupo, S.; Sykes, C.; Ivison, R. J.; Steidel, C. C.; Shapley, A. E.; Vernet, J.; Yamada, T.; Tamura, Y.; Kubo, M.; Nakanishi, K.; Kajisawa, M.; Hatsukade, B.; Kohno, K.

Abstract

Cosmological simulations predict that the Universe contains a network of intergalactic gas filaments, within which galaxies form and evolve. However, the faintness of any emission from these filaments has limited tests of this prediction. We report the detection of rest-frame ultraviolet Lyman-α radiation from multiple filaments extending more than one megaparsec between galaxies within the SSA22 protocluster at a redshift of 3.1. Intense star formation and supermassive black-hole activity is occurring within the galaxies embedded in these structures, which are the likely sources of the elevated ionizing radiation powering the observed Lyman-α emission. Our observations map the gas in filamentary structures of the type thought to fuel the growth of galaxies and black holes in massive protoclusters.

Additional Information

© 2019 American Association for the Advancement of Science. This is an article distributed under the terms of the Science Journals Default License. Received 25 January 2019; accepted 2 September 2019. We thank the reviewers for their constructive comments, which were very helpful in improving this paper. Our data are based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere. We thank all ESO staff who supported us in observation preparation and execution. We thank the JAO and EA-ARC staffs for preparation, observation, and initial data reduction. ALMA is a partnership of ESO (representing its member states), NSF (United States), and NINS (Japan), together with NRC (Canada), NSC and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO, and NAOJ. Some of the data were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. We thank S. Yeh for assistance on the MOSFIRE observations. The observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors recognize and acknowledge the very important cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have had the opportunity to conduct observations from this mountain. Funding: H.U., Y.M., B.H., Y.T., and K.K. are supported by JSPS KAKENHI (grant nos. 17K14252, 25287043/17H04831/17KK0098, 19K03925, 17H06130, and 17H06130, respectively). Y.T. acknowledges support from NAOJ (ALMA Scientific Research grant no. 2018-09B). M.F., I.S., and A.M.S. acknowledge support from the Science and Technology Facilities Council (grant no. ST/P000541/1). This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant no. 757535). C.S. acknowledges an STFC studentship (grant no. ST/R504725/1). S.C. gratefully acknowledges support from the Swiss National Science Foundation (grant no. PP00P2_163824). Author contributions: H.U. led the project and analyzed the data (MUSE, Subaru, ALMA, Keck). M.F., I.S., S.C., and A.M.S. worked on the MUSE data reduction. C.C.S. worked on the Keck data reduction. Y.M. worked on the Subaru data reduction. M.F. and C.S. performed radiative transfer calculations. R.J.I., A.E.S., J.V., T.Y., Y.T., M.Ku., K.N., M.Ka., B.H., and K.K. contributed to interpreting the results. All authors reviewed, discussed, and commented on the results and the manuscript, and met the journal's authorship criteria. Competing interests: The authors declare no competing interests. Data and materials availability: The MUSE data are available in the ESO archive at http://archive.eso.org/cms.html under programs 099.A-0638 and 0101.A-0679; the ALMA data are archived at http://almascience.nrao.edu/aq/ under project codes 2013.1.00162.S, 2015.1.00212.S, and 2016.1.00543.S; and MOSFIRE observations are in the Keck Observatory Archive https://www2.keck.hawaii.edu/koa under semester 2017B, program ID S412. Input parameter files for our CLOUDY simulations are provided in data files S1 and S2.

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