Fermi-LAT Observations of the Diffuse Gamma-Ray Emission: Implications for Cosmic Rays and the Interstellar Medium

Markus Ackermann; Marco Ajello; W. B. Atwood; Luca Baldini; Jean Ballet; Guido Barbiellini; D. Bastieri; K. Bechtol; R. Bellazzini; B. Berenji; R. D. Blandford; E. D. Bloom; E. Bonamente; A. W. Borgland; T. J. Brandt; J. Bregeon; M. Brigida; Pascal Bruel; R. Buehler; S. Buson; G. A. Caliandro; R. A. Cameron; P. A. Caraveo; E. Cavazzuti; C. Cecchi; E. Charles; A. Chekhtman; J. Chiang; S. Ciprini; R. Claus; J. Cohen-Tanugi; J. Conrad; S. Cutini; A. de Angelis; F. de Palma; C. D. Dermer; S. W. Digel; E. Do Couto E Silva; P. S. Drell; A. Drlica-Wagner; L. Falletti; C. Favuzzi; S. J. Fegan; E. C. Ferrara; W. B. Focke; P. Fortin; Y. Fukazawa; S. Fun; P. Fusco; D. Gaggero; F. Gargano; S. Germani; N. Giglietto; F. Giordano; M. Giroletti; T. Glanzman; G. Godfrey; J. E. Grove; S. Guiriec; M. Gustafsson; D. Hadasch; Y. Hanabata; A. K. Harding; M. Hayashida; E. Hays; D. Horan; X. Hou; R. E. Hughes; G. Johannesson; A. S. Johnson; R. P. Johnson; T. Kamae; H. Katagiri; J. Kataoka; Jürgen Knödlseder; M. Kuss; J. Lande; L. Latronico; S.-H. Lee; M. Lemoine-Goumard; F. Longo; F. Loparco; B. Lott; M. N. Lovellette; P. Lubrano; M. N. Mazziotta; J. E. Mcenery; P. F. Michelson; W. Mitthumsiri; T. Mizuno; C. Monte; M. E. Monzani; A. Morselli; I. V. Moskalenko; S. Murgia; M. Naumann-Godo; J. P. Norris; E. Nuss; T. Ohsugi; A. Okumura; N. Omodei; E. Orlando; J. F. Ormes; D. Paneque; J. H. Panetta; D. Parent; M. Pesce-Rollins; M. Pierbattista; F. Piron; G. Pivato; T.A. Porter; S. Raino; R. Rando; M. Razzano; S. Razzaque; A. Reimer; O. Reimer; H. F.-W. Sadrozinski; C. Sgro; E. J. Siskind; G. Spandre; P. Spinelli; A. W. Strong; D. J. Suson; H. Takahashi; T. Tanaka; J. G. Thayer; J. B. Thayer; D. J. Thompson; L. Tibaldo; M. Tinivella; D. F. Torres; G. Tosti; E. Troja; T. L. Usher; J. Vandenbroucke; V. Vasileiou; G. Vianello; V. Vitale; A. P. Waite; P. Wang; B. L. Winer; K. S. Wood; M. Wood; Z. Yang; M. Ziegler; S. Zimmer

doi:10.1088/0004-637X/750/1/3

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Fermi-LAT Observations of the Diffuse Gamma-Ray Emission: Implications for Cosmic Rays and the Interstellar Medium

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Fermi-LAT Observations of the Diffuse Gamma-Ray Emission: Implications for Cosmic Rays and the Interstellar Medium

Markus Ackermann, Marco Ajello, W. B. Atwood, Luca Baldini, Jean Ballet, Guido Barbiellini, D. Bastieri, K. Bechtol, R. Bellazzini, B. Berenji, …

The Astrophysical Journal, Vol.750

2012

DOI: https://doi.org/10.1088/0004-637X/750/1/3

Abstract

cosmic rays

dust

extinction

gamma rays: general

gamma rays: ISM

ISM: general

radiation mechanisms: non-thermal

The gamma-ray sky >100 MeV is dominated by the diffuse emissions from interactions of cosmic rays with the interstellar gas and radiation fields of the Milky Way. Observations of these diffuse emissions provide a tool to study cosmic-ray origin and propagation, and the interstellar medium. We present measurements from the first 21 months of the Fermi-LAT mission and compare with models of the diffuse gamma-ray emission generated using the GALPROP code. The models are fitted to cosmic-ray data and incorporate astrophysical input for the distribution of cosmic-ray sources, interstellar gas and radiation fields. To assess uncertainties associated with the astrophysical input, a grid of models is created by varying within observational limits the distribution of cosmic-ray sources, the size of the cosmic-ray confinement volume (halo), and the distribution of interstellar gas. An all-sky maximum-likelihood fit is used to determine the Xco-factor, the ratio between integrated CO-line intensity and molecular hydrogen column density, the fluxes and spectra of the gamma-ray point sources from the first Fermi-LAT catalogue, and the intensity and spectrum of the isotropic background including residual cosmic rays that were misclassified as gamma rays, all of which have some dependency on the assumed diffuse emission model. The models are compared on the basis of their maximum likelihood ratios as well as spectra, longitude, and latitude profiles. We also provide residual maps for the data following subtraction of the diffuse emission models. The models are consistent with the data at high and intermediate latitudes but under-predict the data in the inner Galaxy for energies above a few GeV. Possible explanations for this discrepancy are discussed, including the contribution by undetected point source populations and spectral variations of cosmic rays throughout the Galaxy.

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Title: Fermi-LAT Observations of the Diffuse Gamma-Ray Emission: Implications for Cosmic Rays and the Interstellar Medium
Creators - without role: Markus Ackermann - Deutsches Elektronen-Synchrotron DESY
Marco Ajello - Kavli Institute for Particle Astrophysics and Cosmology
W. B. Atwood
Luca Baldini - Istituto Nazionale di Fisica Nucleare, Sezione di Pisa
Jean Ballet - Astrophysique, Instrumentation et Modélisation
Guido Barbiellini - University of Trieste
D. Bastieri - University of Padua
K. Bechtol - Kavli Institute for Particle Astrophysics and Cosmology
R. Bellazzini - Istituto Nazionale di Fisica Nucleare, Sezione di Pisa
B. Berenji - Stanford University
R. D. Blandford
E. D. Bloom
E. Bonamente - University of Perugia
A. W. Borgland
T. J. Brandt - Institut de Recherche en Astrophysique et Planétologie
J. Bregeon - Istituto Nazionale di Fisica Nucleare, Sezione di Pisa
M. Brigida - Polytechnic University of Bari
Pascal Bruel - École Polytechnique
R. Buehler - Kavli Institute for Particle Astrophysics and Cosmology
S. Buson - University of Padua
G. A. Caliandro
R. A. Cameron
P. A. Caraveo - Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano
E. Cavazzuti - Agenzia Spaziale Italiana
C. Cecchi - University of Perugia
E. Charles - Kavli Institute for Particle Astrophysics and Cosmology
A. Chekhtman
J. Chiang - Kavli Institute for Particle Astrophysics and Cosmology
S. Ciprini - University of Perugia
R. Claus - Kavli Institute for Particle Astrophysics and Cosmology
J. Cohen-Tanugi - Université de Montpellier, Laboratoire Univers et Particules de Montpellier - LUPM
J. Conrad - Stockholm University
S. Cutini - Agenzia Spaziale Italiana
A. de Angelis - Istituto Nazionale di Fisica Nucleare, Sezione di Trieste
F. de Palma - Istituto Nazionale di Fisica Nucleare, Sezione di Bari
C. D. Dermer
S. W. Digel
E. Do Couto E Silva
P. S. Drell
A. Drlica-Wagner - Kavli Institute for Particle Astrophysics and Cosmology
L. Falletti - Laboratoire Univers et Particules de Montpellier
C. Favuzzi - Polytechnic University of Bari
S. J. Fegan - Laboratoire Leprince-Ringuet
E. C. Ferrara
W. B. Focke
P. Fortin - Centre National de la Recherche Scientifique
Y. Fukazawa - Hiroshima University
S. Fun
P. Fusco - Polytechnic University of Bari
D. Gaggero - Istituto Nazionale di Fisica Nucleare, Sezione di Pisa
F. Gargano - Istituto Nazionale di Fisica Nucleare, Sezione di Bari
S. Germani - University of Perugia
N. Giglietto - Polytechnic University of Bari
F. Giordano - Polytechnic University of Bari
M. Giroletti - Istituto di Radioastronomia di Bologna
T. Glanzman - Stanford University
G. Godfrey - Kavli Institute for Particle Astrophysics and Cosmology
J. E. Grove
S. Guiriec - University of Alabama in Huntsville
M. Gustafsson - Istituto Nazionale di Fisica Nucleare, Sezione di Padova
D. Hadasch - Institute of Space Sciences
Y. Hanabata - Hiroshima University
A. K. Harding
M. Hayashida - Kavli Institute for Particle Astrophysics and Cosmology
E. Hays - Goddard Space Flight Center
D. Horan - Laboratoire Leprince-Ringuet
X. Hou - Laboratoire de Physique des deux infinis Bordeaux
R. E. Hughes
G. Johannesson - University of Iceland
A. S. Johnson
R. P. Johnson
T. Kamae - Kavli Institute for Particle Astrophysics and Cosmology
H. Katagiri - Ibaraki University
J. Kataoka - Waseda University
Jürgen Knödlseder - Centre National de la Recherche Scientifique
M. Kuss - Istituto Nazionale di Fisica Nucleare, Sezione di Pisa
J. Lande - Kavli Institute for Particle Astrophysics and Cosmology
L. Latronico - Istituto Nazionale di Fisica Nucleare, Sezione di Torino
S.-H. Lee - Kyoto University
M. Lemoine-Goumard - Laboratoire de Physique des deux infinis Bordeaux
F. Longo - University of Trieste
F. Loparco - Polytechnic University of Bari
B. Lott - Laboratoire de Physique des deux infinis Bordeaux
M. N. Lovellette
P. Lubrano - University of Perugia
M. N. Mazziotta
J. E. Mcenery
P. F. Michelson
W. Mitthumsiri - Kavli Institute for Particle Astrophysics and Cosmology
T. Mizuno - Hiroshima University
C. Monte - Polytechnic University of Bari
M. E. Monzani
A. Morselli - Istituto Nazionale di Fisica Nucleare, Roma Tor Vergata
I. V. Moskalenko
S. Murgia - Kavli Institute for Particle Astrophysics and Cosmology
M. Naumann-Godo - CEA Paris-Saclay
J. P. Norris
E. Nuss - Université de Montpellier, Laboratoire Univers et Particules de Montpellier - LUPM
T. Ohsugi - Hiroshima University
A. Okumura - Stanford University
N. Omodei - Kavli Institute for Particle Astrophysics and Cosmology
E. Orlando - Kavli Institute for Particle Astrophysics and Cosmology
J. F. Ormes
D. Paneque - Kavli Institute for Particle Astrophysics and Cosmology
J. H. Panetta
D. Parent - George Mason University
M. Pesce-Rollins - Istituto Nazionale di Fisica Nucleare, Sezione di Pisa
M. Pierbattista - Astrophysique, Instrumentation et Modélisation
F. Piron - Université de Montpellier, Laboratoire Univers et Particules de Montpellier - LUPM
G. Pivato - University of Padua
T.A. Porter - Kavli Institute for Particle Astrophysics and Cosmology
S. Raino - Polytechnic University of Bari
R. Rando - University of Padua
M. Razzano - Istituto Nazionale di Fisica Nucleare, Sezione di Pisa
S. Razzaque - George Mason University
A. Reimer - Kavli Institute for Particle Astrophysics and Cosmology
O. Reimer - Kavli Institute for Particle Astrophysics and Cosmology
H. F.-W. Sadrozinski
C. Sgro - Istituto Nazionale di Fisica Nucleare, Sezione di Pisa
E. J. Siskind
G. Spandre - Istituto Nazionale di Fisica Nucleare, Sezione di Pisa
P. Spinelli - Polytechnic University of Bari
A. W. Strong
D. J. Suson
H. Takahashi - Hiroshima University
T. Tanaka - Kavli Institute for Particle Astrophysics and Cosmology
J. G. Thayer
J. B. Thayer
D. J. Thompson
L. Tibaldo - University of Padua
M. Tinivella - Istituto Nazionale di Fisica Nucleare, Sezione di Pisa
D. F. Torres
G. Tosti - Istituto Nazionale di Fisica Nucleare, Sezione di Perugia
E. Troja - Goddard Space Flight Center
T. L. Usher
J. Vandenbroucke - Kavli Institute for Particle Astrophysics and Cosmology
V. Vasileiou - Université de Montpellier, Laboratoire Univers et Particules de Montpellier - LUPM
G. Vianello - Stanford University
V. Vitale - Istituto Nazionale di Fisica Nucleare, Roma Tor Vergata
A. P. Waite
P. Wang - Kavli Institute for Particle Astrophysics and Cosmology
B. L. Winer
K. S. Wood
M. Wood - Kavli Institute for Particle Astrophysics and Cosmology
Z. Yang - Stockholm University
M. Ziegler - University of California, Santa Cruz
S. Zimmer - AlbaNova
Publication Details: The Astrophysical Journal, Vol.750
Identifiers: 9936289509311
Academic Unit: Laboratoire Univers et Particules de Montpellier - LUPM
Language: English
Resource Type: Journal article
Local Fields: in2p3-00685261