Query : 2008A&A...487..837F

2008A&A...487..837F - Astronomy and Astrophysics, volume 487, 837-852 (2008/9-1)

Extragalactic optical-infrared background radiation, its time evolution and the cosmic photon-photon opacity.


Abstract (from CDS):

The background radiation in the optical and the infrared cause energy loss in the propagation of high energy particles through space. In particular, TeV observations with Cherenkov telescopes of extragalactic sources are influenced by the opacity effects due to the interaction of the very high-energy source photons with the background light. With the aim of assessing with the best possible detail these opacity terms, we have modelled the extragalactic optical and infrared backgounds using available information on cosmic sources in the universe from far-UV to sub-millimeter wavelengths over a wide range of cosmic epochs. We have exploited the relevant cosmological survey data - including number counts, redshift distributions, luminosity functions - from ground-based observatories in the optical, near-IR, and sub-millimeter, as well as multi-wavelength information coming from the HST, ISO and Spitzer space telescopes. Additional constraints have been used from direct measurements or upper limits on the extragalactic backgrounds by dedicated missions (COBE). All data were fitted and interpolated with a multi-wavelength backward evolutionary model, allowing us to estimate the background photon density and its redshift evolution. From the redshift-dependent background spectrum, the photon-photon opacities for sources of high-energy emission at any redshifts were then computed. The same results can also be used to compute the optical depths for any kind of processes in the intergalactic space involving interactions with background photons (like scattering of cosmic-ray particles). We have applied our photon-photon opacity estimates to the analysis of spectral data at TeV energies on a few BLAZARs of particular interest. The opacity-corrected TeV spectra are entirely consistent with standard photon-generation processes and show photon indices steeper than Γintrinsic=1.6. Contrary to some previous claims, but in agreement with other reports, we find no evidence for any truly diffuse background components in addition to those from resolved sources. We have tested in particular the effects of a photon background originating at very high redshifts, as would be the emissions by a primeval population of Population III stars around z∼10. We could not identify any opacity features in our studied BLAZAR spectra consistent with such an emission and place a stringent limit on such a diffuse photon intensity of ∼6 nW/m2/sr between 1 and 4 µm. TeV observations of BLAZARs are consistent with background radiation contributed by resolved galaxies in the optical and IR, and exclude prominent additional components from very high-z unresolved sources.

Abstract Copyright:

Journal keyword(s): galaxies: evolution - infrared: galaxies - BL Lacertae objects: general

Simbad objects: 8

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Number of rows : 8
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
1 NAME Chandra Deep Field-South reg 03 32 28.0 -27 48 30           ~ 2003 1
2 NAME GOODS Southern Field reg 03 32 28.0 -27 48 30           ~ 1238 1
3 QSO J1103-2329 BLL 11 03 37.6150845072 -23 29 31.203773520   17.00 16.55 16.61   ~ 356 2
4 Mrk 421 BLL 11 04 27.3140835504 +38 12 31.798495872   13.50 12.90 8.31   ~ 2568 1
5 NAME Hubble Deep Field reg 12 36 49.5 +62 12 58           ~ 1890 1
6 3C 279 Bla 12 56 11.16657958 -05 47 21.5251510   18.01 17.75 15.87   ~ 2923 2
7 4C 39.49 BLL 16 53 52.21668403 +39 45 36.6088754 14.09 14.15 13.29 8.26   ~ 2067 2
8 QSO B2005-489 BLL 20 09 25.3903899240 -48 49 53.725051056   15.75 12.81 11.41   ~ 552 2

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