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INTEGRAL SPI All-Sky View in Soft Gamma Rays: Study of Point Source and Galactic Diffuse Emissions
Bouchet L., Jourdain E., Roques J.P., Strong A., Diehl R. et al
Astrophysical Journal 679 (2008) 1315-1326. - http://hal.in2p3.fr/in2p3-00211785
Physique/Astrophysique/Cosmologie et astrophysique extra-galactique
Planète et Univers/Astrophysique/Cosmologie et astrophysique extra-galactique
INTEGRAL SPI All-Sky View in Soft Gamma Rays: Study of Point Source and Galactic Diffuse Emissions
L. Bouchet1, E. Jourdain1, J. P. Roques1, A. Strong2, R. Diehl2, F. Lebrun3, 4, R. Terrier3, 4
1 :  CESR - Centre d'étude spatiale des rayonnements
CNRS : UMR5187 – Observatoire Midi-Pyrénées – INSU – Université Paul Sabatier (UPS) - Toulouse III
9 Av du colonel Roche - BP 4346 31028 TOULOUSE CEDEX 4
2 :  MPE - Max-Planck-Institut für extraterrestrische Physik
Max Planck Gesellschaft
Postfach 1312 85741 Garching
3 :  APC - UMR 7164 - AstroParticule et Cosmologie
CNRS : UMR7164 – IN2P3 – Observatoire de Paris – Université Paris VII - Paris Diderot – CEA : DSM/IRFU
APC - UMR 7164, Université Paris Diderot, 10 rue Alice Domon et Léonie Duquet, case postale 7020, F-75205 Paris Cedex 13
4 :  DAPNIA - Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée
We have processed the data accumulated with INTEGRAL SPI during 4 years (~ 51 Ms) to study the Galactic ''diffuse'' emission morphology in the 20 keV to 8 MeV energy range. To achieve this objective, we have derived simultaneously an all-sky census of emitting sources and images of the Galactic Ridge (GR) emission. In the central radian, the resolved point source emission amounts to 88%, 91% and 68% of the total emission in the 25-50, 50-100 and 100-300 keV domains respectively. We have compared the GR emission spatial distribution to those obtained from CO and NIR maps, and quantified our results through latitude and longitude profiles. Below 50 keV, the SPI data are better traced by the latter, supporting a stellar origin for this emission. Furthermore, we found that the GR emission spectrum follows a power law with a photon index ~ 1.55 above 50 keV while an additional component is required below this energy. This component shows a cutoff around 30 keV, reinforcing a stellar origin, as proposed by Krivonos et al. (2007). The annihilation diffuse emission component is extracted simultaneously, leading to the determination of the related parameters (positronium flux and fraction). A specific discussion is devoted to the annihilation line distribution since a significant emission is detected over a region as large as ~80 degrees by ~10 degrees potentially associated with the disk or halo surrounding the central regions of our Galaxy.

Articles dans des revues avec comité de lecture
Astrophysical Journal (Astrophys. J.)
Publisher American Astronomical Society
ISSN 0004-637X 

28 pages, 10 figures. Astrophysical journal (accepted for publication)
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