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ALMA Observations of Lyα Blob 1: Multiple Major Mergers and Widely Distributed Interstellar Media

Umehata, Hideki and Smail, Ian and Steidel, Charles C. and Hayes, Matthew and Scott, Douglas and Swinbank, A. M. and Ivison, R. J. and Nagao, Toru and Kubo, Mariko and Nakanishi, Kouichiro and Matsuda, Yuichi and Ikarashi, Soh and Tamura, Yoichi and Geach, J. E. (2021) ALMA Observations of Lyα Blob 1: Multiple Major Mergers and Widely Distributed Interstellar Media. Astrophysical Journal, 918 (2). Art. No. 69. ISSN 0004-637X. doi:10.3847/1538-4357/ac1106.

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We present observations of a giant Lyα blob (LAB) in the SSA22 protocluster at z = 3.1, SSA22-LAB1, taken with the Atacama Large Millimeter/submillimeter Array. Dust continuum, along with [C ii] 158 μm and CO(4–3) line emission have been detected in LAB1, showing complex morphology and kinematics across a ∼100 kpc central region. Seven galaxies at z = 3.0987–3.1016 in the surroundings are identified in [C ii] and dust continuum emission, with two of them potential companions or tidal structures associated with the most massive galaxies. Spatially resolved [C ii] and infrared luminosity ratios for the widely distributed media (L_[Cɪɪ]/L_(IR) ≈ 10⁻²−10⁻³) suggest that the observed extended interstellar media are likely to have originated from star formation activity and the contribution from shocked gas is probably not dominant. LAB1 is found to harbor a total molecular gas mass M_(mol) = (8.7 ± 2.0) × 10¹⁰ M_⊙, concentrated in the core region of the Lyα-emitting area. While (primarily obscured) star formation activity in the LAB1 core is one of the most plausible power sources for the Lyα emission, multiple major mergers found in the core may also play a role in making LAB1 exceptionally bright and extended in Lyα as a result of cooling radiation induced by gravitational interactions.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Umehata, Hideki0000-0003-1937-0573
Smail, Ian0000-0003-3037-257X
Steidel, Charles C.0000-0002-4834-7260
Hayes, Matthew0000-0001-8587-218X
Scott, Douglas0000-0002-6878-9840
Swinbank, A. M.0000-0003-1192-5837
Ivison, R. J.0000-0001-5118-1313
Kubo, Mariko0000-0002-7598-5292
Nakanishi, Kouichiro0000-0002-6939-0372
Matsuda, Yuichi0000-0003-1747-2891
Tamura, Yoichi0000-0003-4807-8117
Geach, J. E.0000-0003-4964-4635
Alternate Title:ALMA Observations of Lyman-alpha Blob 1: Multiple major-mergers and widely distributed interstellar media
Additional Information:© 2021. The American Astronomical Society. Received 2021 April 12; revised 2021 June 22; accepted 2021 July 1; published 2021 September 9. We wish to thank the anonymous referee for constructive comments that improved this paper. We acknowledges valuable discussion with Hidenobu Yajima. We thank Scott Chapman and Ken Mawatari for sharing calibrated optical-to-near-infrared images with us. H.U., Y.M. and K.N. acknowledge support from JSPS KAKENHI grant (17KK0098, 20H01953, 19K03937). I.R.S. acknowledges STFC through grant number ST/T000244/1. R.J.I. is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy—EXC-2094 –390783311. This paper makes use of the following ALMA data: ADS/JAO.ALMA #2013.1.00704.S, #2013.1.00922.S, #2016.1.00485.S, #2016.1.01134.S, #2017.1.01209.S. ALMA is a partnership of ESO (representing its member states), NSF (USA), and NINS (Japan), together with NRC (Canada), MOST 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. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. Our data are based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere. This research is based on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. We are honored and grateful for the opportunity of observing the universe from Maunakea, which is cultural, historical, and natural significance in Hawaii. This research is based on observations made with the NASA/ESA Hubble Space Telescope obtained from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5–26555. Facilities: ALMA - Atacama Large Millimeter Array, Subaru - , VLT(MUSE) - , HST(STIS). - Software: astropy (Astropy Collaboration et al. 2013); casa (McMullin et al. 2007); MUSE pipeline (Weilbacher et al. 2016); mpdaf (Piqueras et al. 2017); (Bacon et al. 2016).
Group:Astronomy Department
Funding AgencyGrant Number
Japan Society for the Promotion of Science (JSPS)17KK0098
Japan Society for the Promotion of Science (JSPS)20H01953
Japan Society for the Promotion of Science (JSPS)19K03937
Science and Technology Facilities Council (STFC)ST/T000244/1
Deutsche Forschungsgemeinschaft (DFG)EXC-2094 -390783311
NASANAS 5-26555
Subject Keywords:Interstellar medium; Intergalactic medium; Starburst galaxies; High-redshift galaxy clusters; Circumgalactic medium
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Interstellar medium (847); Intergalactic medium (813); Starburst galaxies (1570); High-redshift galaxy clusters (2007); Circumgalactic medium (1879)
Record Number:CaltechAUTHORS:20210914-225410693
Persistent URL:
Official Citation:Hideki Umehata et al 2021 ApJ 918 69
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:110903
Deposited By: George Porter
Deposited On:15 Sep 2021 14:09
Last Modified:15 Sep 2021 14:18

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