Diffuse Galactic gamma-ray emission with H.E.S.S

A. Abramowski , F. Aharonian , F. Ait Benkhali , A. G. Akhperjanian , E. O. Angüner , M. Backes , S. Balenderan , Agnès Balzer , A. Barnacka , Y. Becherini , J. Becker Tjus , D. Berge , S. Bernhard , K. Bernlöhr , E. Birsin , J. Biteau (1) , M. Böttcher , C. Boisson (2) , J. Bolmont (3) , P. Bordas , J. Bregeon (4) , F. Brun , P. Brun (5) , M. Bryan , T. Bulik , S. Carrigan , S. Casanova , P. M. Chadwick , N. Chakraborty , R. Chalme-Calvet (3) , R. C. G. Chaves (4) , M. Chrétien (3) , S. Colafrancesco , G. Cologna , J. Conrad , C. Couturier (3) , Y. Cui , I. D. Davids , B. Degrange (1) , C. Deil , P. Dewilt , A. Djannati-Ataï (6) , W. Domainko , A. Donath , L. O'C. Drury , G. Dubus , K. Dutson , J. Dyks , M. Dyrda , T. Edwards , K. Egberts , P. Eger , P. Espigat (6) , C. Farnier , S. Fegan (1) , F. Feinstein (4) , M. V. Fernandes , D. Fernandez (4) , A. Fiasson (7) , G. Fontaine (1) , A. Förster , M. Füssling , S. Gabici (6) , M. Gajdus , Y. A. Gallant (4) , T. Garrigoux (3) , G. Giavitto , B. Giebels (1) , J. F. Glicenstein , D. Gottschall , M. -H. Grondin (8) , M. Grudzińska , D. Hadasch , S. Häffner , J. Hahn , J. Harris , G. Heinzelmann , G. Henri , G. Hermann , O. Hervet (2) , A. Hillert , J. A. Hinton , W. Hofmann , P. Hofverberg , M. Holler , D. Horns , A. Ivascenko , A. Jacholkowska (3) , C. Jahn , M. Jamrozy , M. Janiak , F. Jankowsky , I. Jung-Richardt , M. A. Kastendieck , K. Katarzyński , U. Katz , S. Kaufmann , B. Khélifi (6) , Michel Kieffer (3) , S. Klepser , D. Klochkov , W. Kluźniak , D. Kolitzus , Nu. Komin , K. Kosack , S. Krakau , F. Krayzel (7) , P. P. Krüger , H. Laffon (8) , G. Lamanna (7) , J. Lefaucheur (6) , V. Lefranc , A. Lemière (6) , M. Lemoine-Goumard (8) , J. -P. Lenain (3) , T. Lohse , A. Lopatin , C. -C. Lu , V. Marandon , Alexandre Marcowith (4) , R. Marx , G. Maurin (7) , N. Maxted , M. Mayer , T. J. L. Mccomb , J. Méhault (8) , P. J. Meintjes , U. Menzler , M. Meyer , A. M. W. Mitchell , R. Moderski , M. Mohamed , K. Morå , Emmanuel Moulin (5) , T. Murach , M. de Naurois (1) , J. Niemiec , S. J. Nolan , L. Oakes , H. Odaka , S. Ohm , B. Opitz , M. Ostrowski , I. Oya , M. Panter , R. D. Parsons , M. Paz Arribas , N. W. Pekeur , G. Pelletier , P. -O. Petrucci , B. Peyaud , S. Pita (6) , H. Poon , G. Pühlhofer , M. Punch (6) , A. Quirrenbach , S. Raab , I. Reichardt (6) , A. Reimer , O. Reimer , Matthieu Renaud (4) , R. de Los Reyes , F. Rieger , C. Romoli , S. Rosier-Lees (7) , G. Rowell , B. Rudak , C. B. Rulten (2) , V. Sahakian , D. Salek , D. A. Sanchez (7) , A. Santangelo , R. Schlickeiser , F. Schüssler , A. Schulz , U. Schwanke , S. Schwarzburg , S. Schwemmer , H. Sol (2) , F. Spanier , G. Spengler , F. Spies , Ł. Stawarz , R. Steenkamp , C. Stegmann , F. Stinzing , K. Stycz , I. Sushch , J. -P. Tavernet (3) , T. Tavernier (6) , A. M. Taylor , R. Terrier (6) , M. Tluczykont , C. Trichard (7) , K. Valerius , C. van Eldik , B. van Soelen , George Vasileiadis (4) , J. Veh , C. Venter , A. Viana , P. Vincent (3) , J. Vink , H. J. Völk , F. Volpe , M. Vorster , T. Vuillaume , S. J. Wagner , P. Wagner , R. M. Wagner , M. Ward , M. Weidinger , Q. Weitzel , R. White , A. Wierzcholska , P. Willmann , A. Wörnlein , D. Wouters , R. Yang , V. Zabalza , D. Zaborov (1) , M. Zacharias , A. A. Zdziarski , A. Zech (2) , H. -S. Zechlin , Y. Fukui

1 LLR - Laboratoire Leprince-Ringuet
2 LUTH (UMR_8102) - Laboratoire Univers et Théories
3 LPNHE - Laboratoire de Physique Nucléaire et de Hautes Énergies
4 LUPM - Laboratoire Univers et Particules de Montpellier
5 IRFU - Institut de Recherches sur les lois Fondamentales de l'Univers
6 APC (UMR_7164) - AstroParticule et Cosmologie
7 LAPP - Laboratoire d'Annecy de Physique des Particules
8 CENBG - Centre d'Etudes Nucléaires de Bordeaux Gradignan

Diffuse $\gamma$-ray emission is the most prominent observable signature of celestial cosmic-ray interactions at high energies. While already being investigated at GeV energies over several decades, assessments of diffuse $\gamma$-ray emission at TeV energies remain sparse. After completion of the systematic survey of the inner Galaxy, the H.E.S.S. experiment is in a prime position to observe large-scale diffuse emission at TeV energies. Data of the H.E.S.S. Galactic Plane Survey are investigated in regions off known $\gamma$-ray sources. Corresponding $\gamma$-ray flux measurements were made over an extensive grid of celestial locations. Longitudinal and latitudinal profiles of the observed $\gamma$-ray fluxes show characteristic excess emission not attributable to known $\gamma$-ray sources. For the first time large-scale $\gamma$-ray emission along the Galactic Plane using imaging atmospheric Cherenkov telescopes has been observed. While the background subtraction technique limits the ability to recover modest variation on the scale of the H.E.S.S. field of view or larger, which is characteristic of the inverse Compton scatter-induced Galactic diffuse emission, contributions of neutral pion decay as well as emission from unresolved $\gamma$-ray sources can be recovered in the observed signal to a large fraction. Calculations show that the minimum $\gamma$-ray emission from $\pi^0$-decay represents a significant contribution to the total signal. This detection is interpreted as a mix of diffuse Galactic $\gamma$-ray emission and unresolved sources.

Domaines: Phénomènes cosmiques de haute energie [astro-ph.HE]; Cosmologie et astrophysique extra-galactique [astro-ph.CO]

A. Abramowski, F. Aharonian, F. Ait Benkhali, A. G. Akhperjanian, E. O. Angüner, et al.. Diffuse Galactic gamma-ray emission with H.E.S.S. Physical Review D, 2014, 90 (12), pp.122007. ⟨10.1103/PhysRevD.90.122007⟩. ⟨in2p3-01091552⟩