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

Creators: Umehata, Hideki; Smail, Ian; Steidel, Charles C.; Hayes, Matthew; Scott, Douglas; Swinbank, A. M.; Ivison, R. J.; Nagao, Toru; Kubo, Mariko; Nakanishi, Kouichiro; Matsuda, Yuichi; Ikarashi, Soh; Tamura, Yoichi; Geach, J. E.

Abstract

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.

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).

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