Authors
A Giuliani, M Cardillo, M Tavani, Y Fukui, S Yoshiike, K Torii, G Dubner, G Castelletti, G Barbiellini, A Bulgarelli, P Caraveo, E Costa, PW Cattaneo, A Chen, T Contessi, E Del Monte, I Donnarumma, Y Evangelista, M Feroci, F Gianotti, F Lazzarotto, F Lucarelli, Francesco Longo, M Marisaldi, S Mereghetti, L Pacciani, A Pellizzoni, G Piano, P Picozza, C Pittori, G Pucella, M Rapisarda, A Rappoldi, S Sabatini, P Soffitta, E Striani, M Trifoglio, A Trois, S Vercellone, F Verrecchia, V Vittorini, S Colafrancesco, P Giommi, G Bignami
Publication date
2011/11/11
Journal
The Astrophysical Journal Letters
Volume
742
Issue
2
Pages
L30
Publisher
IOP Publishing
Description
We present the AGILE gamma-ray observations in the energy range 50 MeV–10 GeV of the supernova remnant (SNR) W44, one of the most interesting systems for studying cosmic-ray production. W44 is an intermediate-age SNR (∼ 20, 000 years) and its ejecta expand in a dense medium as shown by a prominent radio shell, nearby molecular clouds, and bright [S ii] emitting regions. We extend our gamma-ray analysis to energies substantially lower than previous measurements which could not conclusively establish the nature of the radiation. We find that gamma-ray emission matches remarkably well both the position and shape of the inner SNR shocked plasma. Furthermore, the gamma-ray spectrum shows a prominent peak near 1 GeV with a clear decrement at energies below a few hundreds of MeV as expected from neutral pion decay. Here we demonstrate that (1) hadron-dominated models are consistent …
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A Giuliani, M Cardillo, M Tavani, Y Fukui, S Yoshiike… - The Astrophysical Journal Letters, 2011