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Stellar Photon Archaeology with Gamma-RaysOngoing deep surveys of galaxy luminosity distribution functions, spectral energy distributions and backwards evolution models of star formation rates can be used to calculate the past history of intergalactic photon densities and, from them, the present and past optical depth of the Universe to gamma-rays from pair production interactions with these photons. The energy-redshift dependence of the optical depth of the Universe to gamma-rays has become known as the Fazio-Stecker relation (Fazio & Stecker 1970). Stecker, Malkan & Scully have calculated the densities of intergalactic background light (IBL) photons of energies from 0.03 eV to the Lyman limit at 13.6 eV and for 0$ < z < $6, using deep survey galaxy observations from Spitzer, Hubble and GALEX and have consequently predicted spectral absorption features for extragalactic gamma-ray sources. This procedure can also be reversed. Determining the cutoff energies of gamma-ray sources with known redshifts using the recently launched Fermi gamma-ray space telescope may enable a more precise determination of the IBL photon densities in the past, i.e., the "archaeo-IBL.", and therefore allow a better measure of the past history of the total star formation rate, including that from galaxies too faint to be observed.
Document ID
20090016210
Acquisition Source
Goddard Space Flight Center
Document Type
Conference Paper
Authors
Stecker, Floyd W.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 24, 2013
Publication Date
April 27, 2009
Subject Category
Astrophysics
Meeting Information
Meeting: Giovanni Fazio Science Symposium
Location: Massachusetts
Country: United States
Start Date: April 27, 2009
End Date: April 28, 2009
Sponsors: Harvard-Smithsonian Center for Astrophysics
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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