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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents



ID: 710053.0, MPI für Astronomie / Publikationen_mpia
Polycyclic aromatic hydrocarbon and mid-infrared continuum emission in a z > 4 submillimeter galaxy
Authors:Riechers, D. A.; Pope, A.; Daddi, E.; Armus, L.; Carilli, C. L.; Walter, F.; Hodge, J.; Chary, R.-R.; Morrison, G. E.; Dickinson, M.; Dannerbauer, H.; Elbaz, D.
Date of Publication (YYYY-MM-DD):2014
Title of Journal:The Astrophysical Journal
Volume:786
Issue / Number:1
Start Page:id. 31 (7 pp)
Audience:Not Specified
Abstract / Description:We report the detection of 6.2 mum polycyclic aromatic hydrocarbon (PAH) and rest-frame 4-7 mum continuum emission in the z = 4.055 submillimeter galaxy GN20, using the Infrared Spectrograph on board the Spitzer Space Telescope. This represents the first detection of PAH emission at z > 4. The strength of the PAH emission feature is consistent with a very high star formation rate of ~1600 M &sun; yr-1. We find that this intense starburst powers at least ~1/3 of the faint underlying 6 mum continuum emission, with an additional, significant (and perhaps dominant) contribution due to a power-law-like hot dust source, which we interpret to likely be a faint, dust-obscured active galactic nucleus (AGN). The inferred 6 mum AGN continuum luminosity is consistent with a sensitive upper limit on the hard X-ray emission as measured by the Chandra X-Ray Observatory if the previously undetected AGN is Compton-thick. This is in agreement with the finding at optical/infrared wavelengths that the galaxy and its nucleus are heavily dust-obscured. Despite the strong power-law component enhancing the mid-infrared continuum emission, the intense starburst associated with the photon-dominated regions that give rise to the PAH emission appears to dominate the total energy output in the infrared. GN20 is one of the most luminous starburst galaxies known at any redshift, embedded in a rich protocluster of star-forming galaxies. This investigation provides an improved understanding of the energy sources that power such exceptional systems, which represent the extreme end of massive galaxy formation at early cosmic times.
Free Keywords:cosmology: observations; galaxies: active; galaxies: formation; galaxies: high-redshift; galaxies: starburst; infrared: galaxies
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:ISSN:0004-637X %R 10.1088/0004-637X/786/1/31
URL:http://cdsads.u-strasbg.fr/abs/2014ApJ...786...31R
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