1. Observations of M31 and M33 with the Fermi Large Area Telescope: A Galactic Center Excess in Andromeda?
- Author
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Jiancheng Wang, Diego F. Torres, Marco Ajello, S. Cutini, Jürgen Knödlseder, L. Latronico, F. Loparco, Ronaldo Bellazzini, R. A. Cameron, S. Rainò, J. F. Ormes, I. A. Grenier, E. Cavazzuti, David H. Green, Gloria Spandre, Jingcheng Li, G. Barbiellini, Andrea Albert, P. Spinelli, R. Buehler, P. Bruel, G. La Mura, Eric Charles, Xian Hou, Nicola Omodei, Kazuhiko Hayashi, Peter F. Michelson, Marcello Giroletti, M. N. Mazziotta, N. Di Lalla, Luca Baldini, Francesco Longo, Jean Ballet, M. Caragiulo, F. Gargano, Giacomo Principe, Claudia Cecchi, D. Malyshev, Sylvain Guiriec, Carmelo Sgrò, Riccardo Rando, Frederic Piron, E. J. Siskind, D. Simone, David Paneque, P. Martin, E. Orlando, M. Razzano, R. Bonino, Filippo D'Ammando, Johan Bregeon, K. Tanaka, A. Chekhtman, C. Favuzzi, Yasunobu Uchiyama, Nestor Mirabal, Elliott D. Bloom, P. Fusco, Matthew Wood, Warit Mitthumsiri, M. Kuss, M. Di Mauro, Matteo Negro, A. Morselli, Francesco Giordano, Stefan Funk, P. Lubrano, F. Spada, R. Caputo, Igor V. Moskalenko, Stefan Larsson, Gabrijela Zaharijas, Olaf Reimer, Melissa Pesce-Rollins, Tsunefumi Mizuno, S. W. Digel, G. Chiaro, R. Desiante, Ming Zhou, Miguel A. Sánchez-Conde, K. S. Wood, T. Ohsugi, Eleonora Troja, T. J. Brandt, L. Di Venere, E. Nuss, Gudlaugur Johannesson, M. E. Monzani, Lucas Guillemot, M. Ackermann, S. Maldera, F. Costanza, T. Kamae, L. Tibaldo, Nicola Giglietto, Elisabetta Bissaldi, Massimo Persic, P. A. Caraveo, T. Glanzman, Denis Bastieri, S. Ciprini, F. de Palma, Eugenio Bottacini, Alberto Manfreda, Albert K. H. Kong, T. A. Porter, Ackermann, M., Ajello, M., Albert, A., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Bellazzini, R., Bissaldi, E., Bloom, E. D., Bonino, R., Bottacini, E., Brandt, T. J., Bregeon, J., Bruel, P., Buehler, R., Cameron, R. A., Caputo, R., Caragiulo, M., Caraveo, P. A., Cavazzuti, E., Cecchi, C., Charles, E., Chekhtman, A., Chiaro, G., Ciprini, S., Costanza, F., Cutini, S., D'Ammando, F., De Palma, F., Desiante, R., Digel, S. W., Di Lalla, N., Di Mauro, M., Di Venere, L., Favuzzi, C., Funk, S., Fusco, P., Gargano, F., Giglietto, N., Giordano, F., Giroletti, M., Glanzman, T., Green, D., Grenier, I. A., Guillemot, L., Guiriec, S., Hayashi, K., Hou, X., Jóhannesson, G., Kamae, T., Knödlseder, J., Kong, A. K. H., Kuss, M., Mura, G. La, Larsson, S., Latronico, L., Li, J., Longo, Francesco, Loparco, F., Lubrano, P., Maldera, S., Malyshev, D., Manfreda, A., Martin, P., Mazziotta, M. N., Michelson, P. F., Mirabal, N., Mitthumsiri, W., Mizuno, T., Monzani, M. E., Morselli, A., Moskalenko, I. V., Negro, M., Nuss, E., Ohsugi, T., Omodei, N., Orlando, E., Ormes, J. F., Paneque, D., Persic, M., Pesce Rollins, M., Piron, F., Porter, T. A., Principe, G., Rainò, S., Rando, R., Razzano, M., Reimer, O., Sánchez Conde, M., Sgrò, C., Simone, D., Siskind, E. J., Spada, F., Spandre, G., Spinelli, P., Tanaka, K., Tibaldo, L., Torres, D. F., Troja, E., Uchiyama, Y., Wang, J. C., Wood, K. S., Wood, M., Zaharijas, G., Zhou, M., Deutsches Elektronen-Synchrotron [Hamburg] (DESY), Department of Physics and Astronomy [Clemson], Clemson University, Los Alamos National Laboratory (LANL), Istituto Nazionale di Fisica Nucleare [Pisa] (INFN), Istituto Nazionale di Fisica Nucleare (INFN), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Istituto Nazionale di Fisica Nucleare, Sezione di Trieste (INFN, Sezione di Trieste), Istituto Nazionale di Fisica Nucleare, Sezione di Padova (INFN, Sezione di Padova), Istituto Nazionale di Fisica Nucleare, sezione di Bari (INFN, sezione di Bari), Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), Stanford University, Laboratoire Univers et Particules de Montpellier (LUPM), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2), Istituto Nazionale di Fisica Nucleare, Sezione di Torino (INFN, Sezione di Torino), NASA Goddard Space Flight Center (GSFC), Laboratoire Leprince-Ringuet (LLR), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Deutsches Elektronen-Synchrotron [Zeuthen] (DESY), Helmholtz-Gemeinschaft = Helmholtz Association, Santa Cruz Institute for Particle Physics (SCIPP), University of California [Santa Cruz] (UCSC), University of California-University of California, Istituto di Astrofisica Spaziale e Fisica Cosmica - Milano (IASF-MI), Istituto Nazionale di Astrofisica (INAF), Agenzia Spaziale Italiana (ASI) Science Data Center, Istituto Nazionale di Fisica Nucleare, Sezione di Perugia (INFN, Sezione di Perugia), George Mason University [Fairfax], Universita degli Studi di Padova, Istituto di Radioastronomia [Bologna] (IRA), Erlangen Centre for Astroparticle Physics (ECAP), Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO), Department of Astrophysics [Nagoya], Nagoya University, Yunnan Observatories, Chinese Academy of Sciences, Science Institute, University of Iceland, University of Iceland [Reykjavik], Tokyo University of Science [Tokyo], Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), National Tsing Hua University [Hsinchu] (NTHU), DIEE, University of Cagliari, Royal Institute of Technology [Stockholm] (KTH ), Institut d'Estudis Espacials de Catalunya (IEEC-CSIC), Mahidol University [Bangkok], Hiroshima University, Istituto Nazionale di Fisica Nucleare, Sezione di Roma Tor Vergata (INFN, Sezione di Roma Tor Vergata), Department of Physics and Astronomy [Denver], University of Denver, Max-Planck-Institut für Physik (Werner-Heisenberg-Institut) (MPI-P), INAF - Osservatorio Astronomico di Trieste (OAT), Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, Leopold-Franzens Universitat Innsbruck, Stockholm University, NYCB Real-Time Computing Inc., Lattingtown, NYCB Real-Time Computing Inc. [Lattingtown], Max-Planck-Institut für Kernphysik (MPIK), Max-Planck-Gesellschaft, Institut de Ciencies de l'Espai [Barcelona] (ICE-CSIC), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Rikkyo University [Tokyo], Università degli Studi di Udine - University of Udine [Italie], ITA, Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), University of California [Santa Cruz] (UC Santa Cruz), University of California (UC)-University of California (UC), Università degli Studi di Padova = University of Padua (Unipd), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Universität Innsbruck [Innsbruck], Ackermann M, Ajello M, Albert A, Baldini L, Ballet J, Barbiellini G, Bastieri D, Bellazzini R, Bissaldi E, Bloom E D, Bonino R, Bottacini E, Brandt T J, Bregeon J, Bruel P, Buehler R, Cameron R A, Caputo R, Caragiulo M, Caraveo P A, Cavazzuti E, Cecchi C, Charles E, Chekhtman A, Chiaro G, Ciprini S, Costanza F, Cutini S, DAmmando F, de Palma F, Desiante R, Digel S W, Di Lalla N, Di Mauro M, Di Venere L, Favuzzi C, Funk S, Fusco P, Gargano F, Giglietto N, Giordano F, Giroletti M, Glanzman T, Green D, Grenier I A, Guillemot L, Guiriec S, Hayashi K, Hou X, Jóhannesson G, Kamae T, Knödlseder J, Kong A K H, Kuss M, La Mura G, Larsson S, Latronico L, Li J, Longo F, Loparco F, Lubrano P, Maldera S, Malyshev D, Manfreda A, Martin P, Mazziotta M N, Michelson P F, Mirabal N, Mitthumsiri W, Mizuno T, Monzani M E, Morselli A, Moskalenko I V, Negro M, Nuss E, Ohsugi T, Omodei N, Orlando E, Ormes J F, Paneque D, Persic M, Pesce-Rollins M, Piron F, Porter T A, Principe G, Rainò S, Rando R, Razzano M, Reimer O, Sánchez-Conde M, Sgrò C, Simone D, Siskind E J, Spada F, Spandre G, Spinelli P, Tanaka K, Tibaldo L, Torres D F, Troja E, Uchiyama Y, Wang J C, Wood K S, Wood M, Zaharijas G, Zhou M, National Institute for Nuclear Physics (INFN), Stanford University [Stanford], Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Helmholtz-Gemeinschaft, Istituto di Radioastronomia INAF, Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Department of Astrophysics, Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), and Consejo Superior de Investigaciones Científicas [Spain] (CSIC)
- Subjects
Andromeda Galaxy ,[SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO] ,cosmic rays ,gamma rays: galaxies ,Local Group ,Astronomy and Astrophysics ,Space and Planetary Science ,Milky Way ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,01 natural sciences ,0103 physical sciences ,Galaxy formation and evolution ,galaxie [gamma rays] ,Interacting galaxy ,10. No inequality ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,cosmic ray ,Physics ,010308 nuclear & particles physics ,Astronomy ,Astronomy and Astrophysic ,Galaxy ,Dwarf spheroidal galaxy ,cosmic rays – gamma rays: galaxies – Local Group ,Globular cluster ,Elliptical galaxy ,ddc:520 ,Astrophysics - High Energy Astrophysical Phenomena - Abstract
The Fermi LAT has opened the way for comparative studies of cosmic rays (CRs) and high-energy objects in the Milky Way (MW) and in other, external, star-forming galaxies. Using 2 yr of observations with the Fermi LAT, local Group galaxy M31 was detected as a marginally extended gamma-ray source, while only an upper limit (UL) has been derived for the other nearby galaxy M33. We revisited the gamma-ray emission in the direction of M31 and M33 using more than 7 yr of LAT Pass 8 data in the energy range 0.1-100 GeV, presenting detailed morphological and spectral analyses. M33 remains undetected and we computed an UL for it. This revised UL remains consistent with the observed correlation between gamma-ray luminosity and star-formation rate tracers and implies an average CR density in M33 that is at most half of that of the MW. M31 is detected with a significance of nearly 10 sigma and to be extended with 4 sigma. Its spectrum is consistent with a power law. The spatial distribution of the emission is consistent with a uniform disk with a radius of 0.4 deg and no offset from the center of M31, but nonuniform intensity distributions cannot be excluded. The flux from M31 appears confined to the inner regions of the galaxy and does not fill the disk or extend far from it. The gamma-ray signal is not correlated with regions rich in gas or star-formation activity suggesting that the emission is not interstellar in origin, unless the energetic particles radiating in gamma rays do not originate in recent star formation. Alternative and nonexclusive interpretations are that the emission results from a population of millisecond pulsars dispersed in the bulge and disk of M31 by disrupted globular clusters or from the decay or annihilation of dark matter particles, similar to what has been proposed to account for the so-called Galactic Center excess found in Fermi-LAT observations of the MW., Comment: 14 pages, 7 figures, 4 tables
- Published
- 2017
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