Gamma-rays from young radio galaxies and quasars. (arXiv:2107.12963v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Principe_G/0/1/0/all/0/1">Giacomo Principe</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Venere_L/0/1/0/all/0/1">Leonardo Di Venere</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Orienti_M/0/1/0/all/0/1">Monica Orienti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Migliori_G/0/1/0/all/0/1">Giulia Migliori</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+DAmmando_F/0/1/0/all/0/1">Filippo D'Ammando</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mazziotta_M/0/1/0/all/0/1">Mario Nicola Mazziotta</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Giroletti_M/0/1/0/all/0/1">Marcello Giroletti</a>
According to radiative models, radio galaxies and quasars are predicted to
produce gamma rays from the earliest stages of their evolution. Exploring their
high-energy emission is crucial for providing information on the most energetic
processes, the origin and the structure of the newly born radio jets. Taking
advantage of more than 11 years of textit{Fermi}-LAT data, we investigate the
gamma-ray emission of 162 young radio sources (103 galaxies and 59 quasars),
the largest sample of young radio sources used so far for such a gamma-ray
study. We separately analyze each source and perform the first stacking
analysis of this class of sources to investigate the gamma-ray emission of the
undetected sources. We detect significant gamma-ray emission from 11 young
radio sources, four galaxies and seven quasars, including the discovery of
significant gamma-ray emission from the compact radio galaxy PKS 1007+142
(z=0.213). The cumulative signal of below-threshold young radio sources is not
significantly detected. However, it is about one order of magnitude below than
those derived from the individual sources, providing stringent upper limits on
the gamma-ray emission from young radio galaxies ($F_{gamma}< 4.6 times
10^{-11}$ ph cm$^{-2}$ s$^{-1}$) and quasars ($F_{gamma}< 10.1 times
10^{-11}$ ph cm$^{-2}$ s$^{-1}$), and enabling a comparison with the models
proposed. With this analysis of more than a decade of textit{Fermi}-LAT
observations, we can conclude that while individual young radio sources can be
bright gamma-ray emitters, the collective gamma-ray emission of this class of
sources is not bright enough to be detected by textit{Fermi}-LAT.
According to radiative models, radio galaxies and quasars are predicted to
produce gamma rays from the earliest stages of their evolution. Exploring their
high-energy emission is crucial for providing information on the most energetic
processes, the origin and the structure of the newly born radio jets. Taking
advantage of more than 11 years of textit{Fermi}-LAT data, we investigate the
gamma-ray emission of 162 young radio sources (103 galaxies and 59 quasars),
the largest sample of young radio sources used so far for such a gamma-ray
study. We separately analyze each source and perform the first stacking
analysis of this class of sources to investigate the gamma-ray emission of the
undetected sources. We detect significant gamma-ray emission from 11 young
radio sources, four galaxies and seven quasars, including the discovery of
significant gamma-ray emission from the compact radio galaxy PKS 1007+142
(z=0.213). The cumulative signal of below-threshold young radio sources is not
significantly detected. However, it is about one order of magnitude below than
those derived from the individual sources, providing stringent upper limits on
the gamma-ray emission from young radio galaxies ($F_{gamma}< 4.6 times
10^{-11}$ ph cm$^{-2}$ s$^{-1}$) and quasars ($F_{gamma}< 10.1 times
10^{-11}$ ph cm$^{-2}$ s$^{-1}$), and enabling a comparison with the models
proposed. With this analysis of more than a decade of textit{Fermi}-LAT
observations, we can conclude that while individual young radio sources can be
bright gamma-ray emitters, the collective gamma-ray emission of this class of
sources is not bright enough to be detected by textit{Fermi}-LAT.
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