skip to main content

SciTech ConnectSciTech Connect

Title: Spectral energy distributions of QSOs at z > 5: Common active galactic nucleus-heated dust and occasionally strong star-formation

We present spectral energy distributions (SEDs) of 69 QSOs at z > 5, covering a rest frame wavelength range of 0.1 μm to ∼80 μm, and centered on new Spitzer and Herschel observations. The detection rate of the QSOs with Spitzer is very high (97% at λ{sub rest} ≲ 4 μm), but drops toward the Herschel bands with 30% detected in PACS (rest frame mid-infrared) and 15% additionally in the SPIRE (rest frame far-infrared; FIR). We perform multi-component SED fits for Herschel-detected objects and confirm that to match the observed SEDs, a clumpy torus model needs to be complemented by a hot (∼1300 K) component and, in cases with prominent FIR emission, also by a cold (∼50 K) component. In the FIR-detected cases the luminosity of the cold component is of the order of 10{sup 13} L {sub ☉} which is likely heated by star formation. From the SED fits we also determine that the active galactic nucleus (AGN) dust-to-accretion disk luminosity ratio declines with UV/optical luminosity. Emission from hot (∼1300 K) dust is common in our sample, showing that nuclear dust is ubiquitous in luminous QSOs out to redshift 6. However, about 15% of the objects appear under-luminous inmore » the near infrared compared to their optical emission and seem to be deficient in (but not devoid of) hot dust. Within our full sample, the QSOs detected with Herschel are found at the high luminosity end in L {sub UV/opt} and L {sub NIR} and show low equivalent widths (EWs) in Hα and in Lyα. In the distribution of Hα EWs, as determined from the Spitzer photometry, the high-redshift QSOs show little difference to low-redshift AGN.« less
Authors:
; ; ; ; ;  [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. Max-Planck Institut für Astronomie (MPIA), Königstuhl 17, D-69117 Heidelberg (Germany)
  2. Universität Wien, Institut für Astrophysik, Türkenschanzstraße 17, A-1180 Wien (Austria)
  3. Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States)
  4. Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)
  5. Astronomisches Institut Ruhr-Universität Bochum, Universitätsstraße 150, D-44801 Bochum (Germany)
Publication Date:
OSTI Identifier:
22357054
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 785; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; COMPARATIVE EVALUATIONS; DETECTION; DISTRIBUTION; DUSTS; EMISSION; ENERGY SPECTRA; FAR INFRARED RADIATION; GALAXIES; GALAXY NUCLEI; LUMINOSITY; PERTURBED ANGULAR CORRELATION; PHOTOMETRY; QUASARS; RED SHIFT; STARS; WAVELENGTHS