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Laporte_2017_ApJ_851_40.pdf
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Final Published Version
Author
Laporte, Nicolas
Nakajima, Kimihiko

Ellis, Richard S.

Zitrin, A.

Stark, Daniel P.
Mainali, Ramesh

Roberts-Borsani, G. W.

Affiliation
Univ Arizona, Steward ObservIssue Date
2017-12-08Keywords
early universegalaxies: distances and redshifts
galaxies: evolution
galaxies: formation
infrared: galaxies
stars: formation
Metadata
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IOP PUBLISHING LTDCitation
A Spectroscopic Search for AGN Activity in the Reionization Era 2017, 851 (1):40 The Astrophysical JournalJournal
The Astrophysical JournalRights
© 2017. The American Astronomical Society. All rights reserved.Collection Information
This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.Abstract
The ubiquity of Lyman alpha (Ly alpha) emission in a sample of four bright [O III]- strong star-forming galaxies with redshifts above seven has led to the suggestion that such luminous sources represent a distinct population compared with their fainter, more numerous counterparts. The presence of Lya emission within the reionization era could indicate that these sources created early ionized bubbles due to their unusually strong radiation, possibly because of the presence of active galactic nuclei. To test this hypothesis, we secured long integration spectra with XSHOOTER on the VLT for three z similar or equal to 7 sources selected to have similar luminosities and prominent excess fluxes in the IRAC 3.6 or 4.5 mu m band, usually attributed to strong [O III] emission. We secured additional spectroscopy for one of these galaxies at z = 7.15 using MOSFIRE at the Keck telescope. For the most well-studied source in our sample with the strongest IRAC excess, we detect significant nebular emission from He II and N V indicative of a non-thermal source. For the other two sources at z = 6.81 and z = 6.85, for which no previous optical/near-infrared spectroscopy was available, Ly alpha is seen in one and C III] emission in the other. Although based on a modest sample, our results further support the hypothesis that the phenomenon of intense [O III] emission is associated preferentially with sources lying in early ionized bubbles. However, even though one of our sources at z = 7.15 suggests the presence of non-thermal radiation, such ionized bubbles may not uniquely arise in this manner. We discuss the unique advantages of extending such challenging diagnostic studies with JWST.ISSN
1538-4357Version
Final published versionSponsors
European Research Council Advanced Grant [FP7/669253]; National Science Foundation [AST-1410155]; NASA [NAS5-26555]; ESO programmes [179.A-2005, 097.A-0043]; W.M. Keck FoundationAdditional Links
http://stacks.iop.org/0004-637X/851/i=1/a=40?key=crossref.d4794d62513b51c285474b20171113ebae974a485f413a2113503eed53cd6c53
10.3847/1538-4357/aa96a8