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Title: Star formation and black hole growth at z ≅ 4.8

We report Herschel/SPIRE, Spitzer and Wide-field Infrared Survey Explorer observations of 44 z ≅ 4.8 optically selected active galactic nuclei (AGNs). This flux-limited sample contains the highest mass black holes (BHs) at this redshift. Ten of the objects were detected by Herschel and five show emission that is not clearly associated with the AGNs. The star formation (SF) luminosity (L{sub SF}) obtained by fitting the spectral energy distribution (SED) with standard SF templates, taking into account AGN contribution, is in the range 10{sup 46.62}-10{sup 47.21} erg s{sup –1} corresponding to SF rates of 1090-4240 M{sub ☉} yr{sup –1}. Fitting with very luminous submillimeter galaxy SEDs gives SF rates that are smaller by 0.05 dex when using all bands and 0.1 dex when ignoring the 250 μm band. A 40 K graybody fits to only the 500 μm fluxes reduce L{sub SF} by about a factor of two. A stacking analysis of 29 undetected sources gives significant signals in all three bands. A SF template fit indicates L{sub SF} = 10{sup 46.19-46.23} erg s{sup –1} depending on the assumed AGN contribution. A 40 K fit to the stacked 500 μm flux gives L{sub SF} = 10{sup 45.95} erg s{sup –1}. Themore » mean BH mass (M{sub BH}) and AGN luminosity (L{sub AGN}) of the detected sources are significantly higher than those of the undetected ones. The spectral differences are seen all the way from UV to far infrared wavelengths. The mean optical-UV spectra are similar to those predicted for thin accretion disks around BHs with similar masses and accretion rates. We suggest two alternative explanations to the correlation of L{sub SF}, L{sub AGN} and M{sub BH}, one involving no AGN feedback and the second involving moderate feedback that affects, but does not totally quench, SF in three-quarters of the sources. We compare our L{sub SF} and L{sub AGN} to lower redshift samples and show a new correlation between L{sub SF} and M{sub BH}. We also examine several rather speculative ideas about the host galaxy properties including the possibility that the detected sources are above the SF mass sequence (MS) at z ≅ 4.8, perhaps in mergers, and most of the undetected sources are on the MS.« less
Authors:
;  [1] ;  [2] ;  [3] ;  [4]
  1. School of Physics and Astronomy and the Wise Observatory, The Raymond and Beverly Sackler Faculty of Exact Sciences, Tel-Aviv University, Tel-Aviv 69978 (Israel)
  2. Department of Physics, Institute for Astronomy, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich (Switzerland)
  3. Department of Physics, University of North Texas, Denton, TX 76203 (United States)
  4. Departamento de Astronomia, Universidad de Chile, Camino del Observatorio 1515, Santiago (Chile)
Publication Date:
OSTI Identifier:
22365381
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 791; Journal Issue: 1; 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; BLACK HOLES; COMPARATIVE EVALUATIONS; CORRELATIONS; EMISSION; ENERGY SPECTRA; FEEDBACK; GALAXIES; GALAXY NUCLEI; INFRARED SURVEYS; LUMINOSITY; MASS; QUASARS; RED SHIFT; STARS; ULTRAVIOLET SPECTRA