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An Intensely Star-forming Galaxy at z ~ 7 with Low Dust and Metal Content Revealed by Deep ALMA and HST Observations

Ouchi, Masami and Ellis, Richard and Ono, Yoshiaki and Nakanishi, Kouichiro and Kohno, Kotaro and Momose, Rieko and Kurono, Yasutaka and Ashby, M. L. N. and Shimasaku, Kazuhiro and Willner, S. P. and Fazio, G. G. and Tamura, Yoichi and Iono, Daisuke (2013) An Intensely Star-forming Galaxy at z ~ 7 with Low Dust and Metal Content Revealed by Deep ALMA and HST Observations. Astrophysical Journal, 778 (2). Art. No. 102. ISSN 0004-637X. https://resolver.caltech.edu/CaltechAUTHORS:20131122-074440599

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Abstract

We report deep ALMA observations complemented by associated Hubble Space Telescope (HST) imaging for a luminous (m_(UV) = 25) galaxy, "Himiko," at a redshift of z = 6.595. The galaxy is remarkable for its high star formation rate, 100 M_☉ yr^(−1), which has been securely estimated from our deep HST and Spitzer photometry, and the absence of any evidence for strong active galactic nucleus activity or gravitational lensing magnification. Our ALMA observations probe an order of magnitude deeper than previous IRAM observations, yet fail to detect a 1.2 mm dust continuum, indicating a flux of <52 μJy, which is comparable to or weaker than that of local dwarf irregulars with much lower star formation rates. We likewise provide a strong upper limit for the flux of [C II] 158 μm, L_([C II]) < 5.4 x 10^7 L_☉, which is a diagnostic of the hot interstellar gas that is often described as a valuable probe for early galaxies. In fact, our observations indicate that Himiko lies off the local L_([C II])–star formation rate scaling relation by a factor of more than 30. Both aspects of our ALMA observations suggest that Himiko is a unique object with a very low dust content and perhaps nearly primordial interstellar gas. Our HST images provide unique insight into the morphology of this remarkable source, highlighting an extremely blue core of activity and two less extreme associated clumps. Himiko is undergoing a triple major merger event whose extensive ionized nebula of Lyα emitting gas, discovered in our earlier work with Subaru, is powered by star formation and the dense circumgalactic gas. We are likely witnessing an early massive galaxy during a key period of its mass assembly close to the end of the reionization era.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1088/0004-637X/778/2/102DOIArticle
http://arxiv.org/abs/1306.3572arXivDiscussion Paper
ORCID:
AuthorORCID
Ouchi, Masami0000-0002-1049-6658
Ellis, Richard0000-0001-7782-7071
Kohno, Kotaro0000-0002-4052-2394
Ashby, M. L. N.0000-0002-3993-0745
Willner, S. P.0000-0002-9895-5758
Fazio, G. G.0000-0002-0670-0708
Iono, Daisuke0000-0002-2364-0823
Additional Information:© 2013 The American Astronomical Society. Received 2013 June 15; accepted 2013 August 23; published 2013 November 11. We are grateful to Pratika Dayal, Andrea Ferrara, Rob Kennicutt, Kyoungsoo Lee, Masao Mori, Dominik Riechers, Dimitra Rigopoulou, Daniel Schaerer, Masayuki Umemura, Fabian Walter, and Chris Willott for their useful comments and discussions. We thank the ALMA observatory and HST support staff for their invaluable help that made these pioneering observations possible. The HST reduction was supported by a NASA STScI grant GO 12265. This work was supported by World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan, and KAKENHI (23244025) Grant-in-Aid for Scientific Research (A) through Japan Society for the Promotion of Science (JSPS). This paper makes use of the following ALMA data: ADS/JAO.ALMA#2011.0.00115.S. ALMA is a partnership of ESO (representing its member states), NSF (USA), and NINS (Japan), together with NRC (Canada), NSC, and ASIAA (Taiwan), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO, and NAOJ. This work is based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program #12265. Support for program #12265 was provided by NASA through a grant 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. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. Facilities: ALMA (Band6) - Atacama Large Millimeter Array HST (WFC3-IR) - Hubble Space Telescope satellite Spitzer (IRAC) - Spitzer Space Telescope satellite
Group:Infrared Processing and Analysis Center (IPAC)
Funders:
Funding AgencyGrant Number
NASAGO 12265
Ministry of Education, Culture, Sports, Science and Technology (MEXT)UNSPECIFIED
Japan Society for the Promotion of Science (JSPS)23244025
NASANAS 5-26555
NASA/JPL/CaltechUNSPECIFIED
Subject Keywords:cosmology: observations – galaxies: formation – galaxies: high-red
Issue or Number:2
Record Number:CaltechAUTHORS:20131122-074440599
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20131122-074440599
Official Citation:An Intensely Star-forming Galaxy at z ~ 7 with Low Dust and Metal Content Revealed by Deep ALMA and HST Observations Masami Ouchi et al. 2013 ApJ 778 102
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:42637
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:24 Nov 2013 00:00
Last Modified:04 Nov 2019 04:33

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