# The contribution of the Unresolved Extragalactic Radio Sources to the Brightness Temperature of the sky - Astrophysics

Abstract: The contribution of the Unresolved Extragalactic Radio Sources to the diffusebrightness of the sky was evaluated using the source number - flux measurementsavailable in literature. We first optimized the fitting function of the databased on number counts distribution. We then computed the brightnesstemperature at various frequencies from 151 MHz to 8440 MHz and derived itsspectral dependence. As expected the frequency dependence can be described by apower law with a spectral index $\gamma \simeq -2.7$, in agreement with theflux emitted by the {\it steep spectrum} sources. The contribution of {\it flatspectrum} sources becomes relevant at frequencies above several GHz. Using thedata available in literature we improved our knowledge of the brightness of theunresolved extragalactic radio sources. The results obtained have generalvalidity and they can be used to disentangle the various contributions of thesky brightness and to evaluate the CMB temperature.

Author: M. Gervasi, A. Tartari, M. Zannoni, G. Boella, G. Sironi

Source: https://arxiv.org/