GAMMA-RAY OBSERVATIONS OF THE ORION MOLECULAR CLOUDS WITH THE FERMI LARGE AREA TELESCOPE

Markus Ackermann; Marco Ajello; A. Allafort; E. Antolini; 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; E. Bottacini; T. J. Brandt; J. Bregeon; M. Brigida; Pascal Bruel; R. Buehler; S. Buson; G. A. Caliandro; R. A. Cameron; P. A. Caraveo; C. Cecchi; A. Chekhtman; J. Chiang; S. Ciprini; R. Claus; J. Cohen-Tanugi; J. Conrad; F. d'Ammando; A. de Angelis; F. de Palma; C. D. Dermer; E. Do Couto E Silva; P. S. Drell; A. Drlica-Wagner; T. Enoto; L. Falletti; C. Favuzzi; S. J. Fegan; E. C. Ferrara; W. B. Focke; Y. Fukazawa; Y. Fukui; P. Fusco; F. Gargano; D. Gasparrini; S. Germani; N. Giglietto; F. Giordano; M. Giroletti; T. Glanzman; G. Godfrey; S. Guiriec; D. Hadasch; Y. Hanabata; A. K. Harding; M. Hayashida; K. Hayashi; D. Horan; X. Hou; R. E. Hughes; M. S. Jackson; G. J 'Ohannesson; A. S. Johnson; T. Kamae; H. Katagiri; J. Kataoka; M. Kerr; Jürgen Knödlseder; M. Kuss; J. Lande; S. Larsson; S.-H. Lee; F. Longo; F. Loparco; M. N. Lovellette; P. Lubrano; K. Makishima; M. N. Mazziotta; J. Mehault; W. Mitthumsiri; A. A. Moiseev; C. Monte; M. E. Monzani; A. Morselli; I. V. Moskalenko; S. Murgia; T. Nakamori; M. Naumann-Godo; S. Nishino; J. P. Norris; E. Nuss; M. Ohno; T. Ohsugi; A. Okumura; M. Orienti; E. Orlando; J. F. Ormes; M. Ozaki; D. Paneque; J. H. Panetta; D. Parent; V. Pelassa; M. Pesce-Rollins; M. Pierbattista; F. Piron; G. Pivato; T.A. Porter; S. Rain'O; M. Razzano; A. Reimer; O. Reimer; M. Roth; H. F.-W. Sadrozinski; C. Sgr'O; E. J. Siskind; G. Spandre; P. Spinelli; A. W. Strong; H. Takahashi; T. Takahashi; T. Tanaka; J. G. Thayer; J. B. Thayer; O. Tibolla; M. Tinivella; D. F. Torres; A. Tramacere; E. Troja; Y. Uchiyama; T. L. Usher; J. Vandenbroucke; V. Vasileiou; G. Vianello; V. Vitale; A. P. Waite; P. Wang; B. L. Winer; K. S. Wood; Z. Yang; S. Zimmer

doi:10.1088/0004-637X/756/1/4

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GAMMA-RAY OBSERVATIONS OF THE ORION MOLECULAR CLOUDS WITH THE FERMI LARGE AREA TELESCOPE

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GAMMA-RAY OBSERVATIONS OF THE ORION MOLECULAR CLOUDS WITH THE FERMI LARGE AREA TELESCOPE

Markus Ackermann, Marco Ajello, A. Allafort, E. Antolini, Luca Baldini, Jean Ballet, Guido Barbiellini, D. Bastieri, K. Bechtol, R. Bellazzini, …

The Astrophysical Journal, Vol.756

2012

DOI: https://doi.org/10.1088/0004-637X/756/1/4

Abstract

gamma rays: ISM

ISM: clouds

ISM: general

ISM: individual objects (Orion A and Orion B) Online-only material: color figures

We report on the gamma-ray observations of giant molecular clouds Orion A and B with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. The gamma-ray emission in the energy band between ∼100 MeV and ∼100 GeV is predicted to trace the gas mass distribution in the clouds through nuclear interactions between the Galactic cosmic rays (CRs) and interstellar gas. The gamma-ray production cross-section for the nuclear interaction is known to ∼10% precision which makes the LAT a powerful tool to measure the gas mass column density distribution of molecular clouds for a known CR intensity. We present here such distributions for Orion A and B, and correlate them with those of the velocity-integrated CO intensity (WCO) at a 1◦ × 1◦ pixel level. The correlation is found to be linear over a WCO range of ∼10-fold when divided in three regions, suggesting penetration of nuclear CRs to most of the cloud volumes. The WCO-to-mass conversion factor, XCO, is found to be ∼2.3 × 1020 cm−2 (K km s−1)−1 for the high-longitude part of Orion A (l > 212◦), ∼1.7 times higher than ∼1.3 × 1020 found for the rest of Orion A and B. We interpret the apparent high XCO in the high-longitude region of Orion A in the light of recent works proposing a nonlinear relation between H2 and CO densities in the diffuse molecular gas. WCO decreases faster than the H2 column density in the region making the gas "darker" to WCO.

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Title: GAMMA-RAY OBSERVATIONS OF THE ORION MOLECULAR CLOUDS WITH THE FERMI LARGE AREA TELESCOPE
Creators - without role: Markus Ackermann - Deutsches Elektronen-Synchrotron DESY
Marco Ajello - Stanford University
A. Allafort - Kavli Institute for Particle Astrophysics and Cosmology
E. Antolini - Istituto Nazionale di Fisica Nucleare, Sezione di Perugia
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 - Kavli Institute for Particle Astrophysics and Cosmology
R. D. Blandford
E. D. Bloom
E. Bonamente - University of Perugia
A. W. Borgland
E. Bottacini - Kavli Institute for Particle Astrophysics and Cosmology
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
C. Cecchi - University of Perugia
A. Chekhtman - George Mason University
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
F. d'Ammando
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
E. Do Couto E Silva
P. S. Drell
A. Drlica-Wagner - Stanford University
T. Enoto - 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
Y. Fukazawa - Hiroshima University
Y. Fukui - Nagoya University
P. Fusco - Polytechnic University of Bari
F. Gargano - Istituto Nazionale di Fisica Nucleare, Sezione di Bari
D. Gasparrini - Agenzia Spaziale Italiana
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
S. Guiriec - University of Alabama in Huntsville
D. Hadasch - Institute of Space Sciences
Y. Hanabata - Hiroshima University
A. K. Harding
M. Hayashida - Kyoto University
K. Hayashi - Hiroshima University
D. Horan - Laboratoire Leprince-Ringuet
X. Hou - Laboratoire de Physique des deux infinis Bordeaux
R. E. Hughes
M. S. Jackson
G. J 'Ohannesson
A. S. Johnson
T. Kamae - SLAC National Accelerator Laboratory
H. Katagiri - Ibaraki University
J. Kataoka - Waseda University
M. Kerr - Kavli Institute for Particle Astrophysics and Cosmology
Jürgen Knödlseder - Université de Toulouse
M. Kuss - Istituto Nazionale di Fisica Nucleare, Sezione di Pisa
J. Lande - Kavli Institute for Particle Astrophysics and Cosmology
S. Larsson - Stockholm University
S.-H. Lee - Kyoto University
F. Longo - University of Trieste
F. Loparco - Polytechnic University of Bari
M. N. Lovellette
P. Lubrano - University of Perugia
K. Makishima - The University of Tokyo
M. N. Mazziotta
J. Mehault - Université de Montpellier, Laboratoire Univers et Particules de Montpellier - LUPM
W. Mitthumsiri - Kavli Institute for Particle Astrophysics and Cosmology
A. A. Moiseev
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
T. Nakamori - Waseda University
M. Naumann-Godo - CEA Paris-Saclay
S. Nishino - Hiroshima University
J. P. Norris
E. Nuss - Université de Montpellier, Laboratoire Univers et Particules de Montpellier - LUPM
M. Ohno - Istituto Nazionale di Fisica Nucleare, Roma Tor Vergata
T. Ohsugi - Hiroshima University
A. Okumura - Institute of Space and Astronautical Science
M. Orienti - Istituto di Radioastronomia di Bologna
E. Orlando - Kavli Institute for Particle Astrophysics and Cosmology
J. F. Ormes
M. Ozaki - Institute of Space and Astronautical Science
D. Paneque - Max Planck Institute for Physics
J. H. Panetta
D. Parent - George Mason University
V. Pelassa - Université de Montpellier, Laboratoire Univers et Particules de Montpellier - LUPM
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. Rain'O
M. Razzano - University of California, Santa Cruz
A. Reimer - Kavli Institute for Particle Astrophysics and Cosmology
O. Reimer - Kavli Institute for Particle Astrophysics and Cosmology
M. Roth - Universität Innsbruck
H. F.-W. Sadrozinski
C. Sgr'O
E. J. Siskind
G. Spandre - Istituto Nazionale di Fisica Nucleare, Sezione di Pisa
P. Spinelli - Polytechnic University of Bari
A. W. Strong
H. Takahashi - Hiroshima University
T. Takahashi - Institute of Space and Astronautical Science
T. Tanaka - Kavli Institute for Particle Astrophysics and Cosmology
J. G. Thayer
J. B. Thayer
O. Tibolla - University of Würzburg
M. Tinivella - Istituto Nazionale di Fisica Nucleare, Sezione di Pisa
D. F. Torres
A. Tramacere - Swiss Data Science Center
E. Troja - Goddard Space Flight Center
Y. Uchiyama - Stanford University
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 - Consorzio Interuniversitario Fisica Spaziale
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
Z. Yang - AlbaNova
S. Zimmer - AlbaNova
Publication Details: The Astrophysical Journal, Vol.756
Identifiers: 9939470509311
Academic Unit: Laboratoire Univers et Particules de Montpellier - LUPM
Language: English
Resource Type: Journal article
Local Fields: in2p3-00747339