A $gamma$-ray determination of the Universe’s star-formation history. (arXiv:1812.01031v1 [astro-ph.HE])

A $gamma$-ray determination of the Universe’s star-formation history. (arXiv:1812.01031v1 [astro-ph.HE])
The <a href="http://arxiv.org/find/astro-ph/1/au:+Collaboration_Fermi_LAT/0/1/0/all/0/1">Fermi-LAT Collaboration. Contact Authors</a>: <a href="http://arxiv.org/find/astro-ph/1/au:+Ajello_M/0/1/0/all/0/1">M. Ajello</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Helgason_K/0/1/0/all/0/1">K. Helgason</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Paliya_V/0/1/0/all/0/1">V. Paliya</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Finke_J/0/1/0/all/0/1">J. Finke</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dominguez_A/0/1/0/all/0/1">A. Dominguez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Desai_A/0/1/0/all/0/1">A. Desai</a>

The light emitted by all galaxies over the history of the Universe produces
the extragalactic background light (EBL) at ultraviolet, optical, and infrared
wavelengths. The EBL is a source of opacity for $gamma$ rays via photon-photon
interactions, leaving an imprint in the spectra of distant $gamma$-ray
sources. We measure this attenuation using {739} active galaxies and one
gamma-ray burst detected by the {it Fermi} Large Area Telescope. This allows
us to reconstruct the evolution of the EBL and determine the star-formation
history of the Universe over 90% of cosmic time. Our star-formation history is
consistent with independent measurements from galaxy surveys, peaking at
redshift $zsim2$. Upper limits of the EBL at the epoch of re-ionization
suggest a turnover in the abundance of faint galaxies at $zsim 6$.

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