Journal
ASTROPHYSICAL JOURNAL
Volume 772, Issue 2, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/772/2/103
Keywords
galaxies: active; infrared: galaxies; quasars: general
Categories
Funding
- National Aeronautics and Space Administration
- DFG [LE 3042/1-1]
- NSF [AST 08-06861, 11-07682]
- Nordrhein-Westfalische Akademie der Wissenschaften und der Kunste
- Direct For Mathematical & Physical Scien
- Division Of Astronomical Sciences [1107682] Funding Source: National Science Foundation
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [806861] Funding Source: National Science Foundation
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We present Herschel far-infrared (FIR) photometry of 11 quasars at redshiftz > 5 that have previously been detected at 1.2 mm. We perform full spectral energy distribution (SED) fits over the wavelength range lambda(rest) similar to 0.1-400 mu m for those objects with good Herschel detections. These fits reveal the need for an additional FIR component besides the emission from a dusty active galactic nucleus (AGN)-powered torus. This additional FIR component has temperatures of T-FIR similar to 40-60 K with luminosities of L8-1000 (mu m) similar to 10(13) L-circle dot (accounting for 25%-60% of the bolometric FIR luminosity). If the FIR dust emission is due to star formation it would suggest star formation rates in excess of 1000 solar masses per year. We show that at long wavelengths (lambda(rest) greater than or similar to 50 mu m) the contribution of the AGN-powered torus emission is negligible. This explains how previous FIR studies of high-redshift quasars that relied on single-component fits to (ground-based) observations at lambda(obs) greater than or similar to 350 mu m reached T-FIR and L-FIR values similar to our complete SED fits. Stacking the Herschel data of four individually undetected sources reveals a significant average signal in the PACS bands but not in SPIRE. The average SED of sources with individual Herschel detections shows a striking surplus in near-and mid-infrared (MIR) emission when compared to common AGN templates. The comparison between two average SEDs (sources with and without individual Herschel detections) matched in the UV/optical indicates that for these objects the strength of the MIR emission may correlate with the strength of the FIR emission.
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