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dc.contributor.authorLaporte, Nicolas
dc.contributor.authorNakajima, Kimihiko
dc.contributor.authorEllis, Richard S.
dc.contributor.authorZitrin, A.
dc.contributor.authorStark, Daniel P.
dc.contributor.authorMainali, Ramesh
dc.contributor.authorRoberts-Borsani, G. W.
dc.date.accessioned2018-01-30T22:46:28Z
dc.date.available2018-01-30T22:46:28Z
dc.date.issued2017-12-08
dc.identifier.citationA Spectroscopic Search for AGN Activity in the Reionization Era 2017, 851 (1):40 The Astrophysical Journalen
dc.identifier.issn1538-4357
dc.identifier.doi10.3847/1538-4357/aa96a8
dc.identifier.urihttp://hdl.handle.net/10150/626417
dc.description.abstractThe 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.
dc.description.sponsorshipEuropean 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 Foundationen
dc.language.isoenen
dc.publisherIOP PUBLISHING LTDen
dc.relation.urlhttp://stacks.iop.org/0004-637X/851/i=1/a=40?key=crossref.d4794d62513b51c285474b20171113eben
dc.rights© 2017. The American Astronomical Society. All rights reserved.en
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/
dc.subjectearly universeen
dc.subjectgalaxies: distances and redshiftsen
dc.subjectgalaxies: evolutionen
dc.subjectgalaxies: formationen
dc.subjectinfrared: galaxiesen
dc.subjectstars: formationen
dc.titleA Spectroscopic Search for AGN Activity in the Reionization Eraen
dc.typeArticleen
dc.contributor.departmentUniv Arizona, Steward Observen
dc.identifier.journalThe Astrophysical Journalen
dc.description.collectioninformationThis 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.en
dc.eprint.versionFinal published versionen
refterms.dateFOA2018-05-28T11:56:02Z
html.description.abstractThe 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.


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