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ALMA Observations of Lyα Blob 1: Halo Substructure Illuminated from Within

Geach, J.E.; Narayanan, D.; Matsuda, Y.; Hayes, M.; Mas-Ribas, Ll; Dijkstra, M.; Steidel, C.C.; Chapman, S.C.; Feldmann, R.; Avison, A.; Agertz, O.; Ao, Y.; Birkinshaw, M.; Bremer, M.N.; Clements, D.L.; Dannerbauer, H.; Farrah, D.; Harrison, C.M.; Kubo, M.; Michałowski, M.J.; Scott, Douglas; Smith, D.J.B.; Spaans, M.; Simpson, J.M.; Swinbank, A.M.; Taniguchi, Y.; van der Werf, P.; Verma, A.; Yamada, T.

ALMA Observations of Lyα Blob 1: Halo Substructure Illuminated from Within Thumbnail


J.E. Geach

D. Narayanan

Y. Matsuda

M. Hayes

Ll Mas-Ribas

M. Dijkstra

C.C. Steidel

S.C. Chapman

R. Feldmann

A. Avison

O. Agertz

Y. Ao

M. Birkinshaw

M.N. Bremer

D.L. Clements

H. Dannerbauer

D. Farrah

C.M. Harrison

M. Kubo

M.J. Michałowski

Douglas Scott

D.J.B. Smith

M. Spaans

J.M. Simpson

Y. Taniguchi

P. van der Werf

A. Verma

T. Yamada


We present new Atacama Large Millimeter/Submillimeter Array (ALMA) 850 μm continuum observations of the original Lyα Blob (LAB) in the SSA22 field at z = 3.1 (SSA22-LAB01). The ALMA map resolves the previously identified submillimeter source into three components with a total flux density of S 850 = 1.68 ± 0.06 mJy, corresponding to a star-formation rate of ~150 M ⊙ yr−1. The submillimeter sources are associated with several faint (m ≈ 27 mag) rest-frame ultraviolet sources identified in Hubble Space Telescope Imaging Spectrograph (STIS) clear filter imaging (λ ≈ 5850 Å). One of these companions is spectroscopically confirmed with the Keck Multi-Object Spectrometer For Infra-Red Exploration to lie within 20 projected kpc and 250 km s−1 of one of the ALMA components. We postulate that some of these STIS sources represent a population of low-mass star-forming satellites surrounding the central submillimeter sources, potentially contributing to their growth and activity through accretion. Using a high-resolution cosmological zoom simulation of a 1013 M ⊙ halo at z = 3, including stellar, dust, and Lyα radiative transfer, we can model the ALMA+STIS observations and demonstrate that Lyα photons escaping from the central submillimeter sources are expected to resonantly scatter in neutral hydrogen, the majority of which is predicted to be associated with halo substructure. We show how this process gives rise to extended Lyα emission with similar surface brightness and morphology to observed giant LABs.


Geach, J., Narayanan, D., Matsuda, Y., Hayes, M., Mas-Ribas, L., Dijkstra, M., …Yamada, T. (2016). ALMA Observations of Lyα Blob 1: Halo Substructure Illuminated from Within. Astrophysical Journal, 832(1), Article 37.

Journal Article Type Article
Acceptance Date Aug 8, 2016
Online Publication Date Nov 14, 2016
Publication Date Nov 14, 2016
Deposit Date Mar 9, 2017
Publicly Available Date Mar 9, 2017
Journal Astrophysical Journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 832
Issue 1
Article Number 37


Published Journal Article (2.7 Mb)

Copyright Statement
© 2016. The American Astronomical Society. All rights reserved.

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