Unresolved Gamma-Ray Sky through its Angular Power Spectrum
Abstract
The gamma-ray sky has been observed with unprecedented accuracy in the last decade by the Fermi large area telescope (LAT), allowing us to resolve and understand the high-energy Universe. The nature of the remaining unresolved emission (unresolved gamma-ray background, UGRB) below the LAT source detection threshold can be uncovered by characterizing the amplitude and angular scale of the UGRB fluctuation field. This work presents a measurement of the UGRB autocorrelation angular power spectrum based on eight years of Fermi LAT Pass 8 data products. The analysis is designed to be robust against contamination from resolved sources and noise systematics. The sensitivity to subthreshold sources is greatly enhanced with respect to previous measurements. We find evidence (with 3.7 significance) that the scenario in which two classes of sources contribute to the UGRB signal is favored over a single class. A double power law with exponential cutoff can explain the anisotropy energy spectrum well, with photon indices of the two populations being 2.55 0.23 and 1.86 0.15.
Keywords
Cite
@article{arxiv.1812.02079,
title = {Unresolved Gamma-Ray Sky through its Angular Power Spectrum},
author = {M. Ackermann and M. Ajello and L. Baldini and J. Ballet and G. Barbiellini and D. Bastieri and R. Bellazzini and E. Bissaldi and R. D. Blandford and R. Bonino and E. Bottacini and J. Bregeon and P. Bruel and R. Buehler and E. Burns and S. Buson and R. A. Cameron and R. Caputo and P. A. Caraveo and E. Cavazzuti and S. Chen and G. Chiaro and S. Ciprini and D. Costantin and A. Cuoco and S. Cutini and F. D'Ammando and P. de la Torre Luque and F. de Palma and A. Desai and S. W. Digel and N. Di Lalla and M. Di Mauro and L. Di Venere and F. Fana Dirirsa and C. Favuzzi and A. Franckowiak and Y. Fukazawa and S. Funk and P. Fusco and F. Gargano and D. Gasparrini and N. Giglietto and F. Giordano and M. Giroletti and D. Green and I. A. Grenier and L. Guillemot and S. Guiriec and D. Horan and G. Johannesson and M. Kuss and S. Larsson and L. Latronico and J. Li and I. Liodakis and F. Longo and F. Loparco and P. Lubrano and J. D. Magill and S. Maldera and D. Malyshev and A. Manfreda and M. N. Mazziotta and I. Mereu and P. F. Michelson and W. Mitthumsiri and T. Mizuno and M. E. Monzani and A. Morselli and I. V. Moskalenko and M. Negro and E. Nuss and M. Orienti and E. Orlando and M. Palatiello and V. S. Paliya and D. Paneque and M. Persic and M. Pesce-Rollins and V. Petrosian and F. Piron and T. A. Porter and G. Principe and S. Raino and R. Rando and M. Razzano and S. Razzaque and A. Reimer and O. Reimer and D. Serini and C. Sgro and E. J. Siskind and G. Spandre and P. Spinelli and D. J. Suson and H. Tajima and M. Takahashi and J. B. Thayer and L. Tibaldo and D. F. Torres and E. Troja and T. M. Venters and G. Vianello and K. Wood and M. Yassine and G. Zaharijas and S. Ammazzalorso and N. Fornengo and M. Regis},
journal= {arXiv preprint arXiv:1812.02079},
year = {2019}
}
Comments
8 + 12 (SOM) pages, Contact author: Michela Negro (michela.negro@to.infn.it). (Typos in Tab. VII in previous versions)