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Cosmic-ray electron-positron spectrum from 7 GeV to 2 TeV with the Fermi Large Area Telescope

Physical Review D 2017年第8期95卷 082007-082007页

作者： S. Abdollahi M. Ackermann M. Ajello W. B. Atwood L. Baldini G. Barbiellini D. Bastieri R. Bellazzini E. D. Bloom R. Bonino T. J. Brandt J. Bregeon P. Bruel R. Buehler R. A. Cameron R. Caputo M. Caragiulo D. Castro E. Cavazzuti C. Cecchi A. Chekhtman S. Ciprini J. Cohen-Tanugi F. Costanza A. Cuoco S. Cutini F. D’Ammando F. de Palma R. Desiante S. W. Digel N. Di Lalla M. Di Mauro L. Di Venere P. S. Drell A. Drlica-Wagner C. Favuzzi W. B. Focke S. Funk P. Fusco F. Gargano D. Gasparrini N. Giglietto F. Giordano M. Giroletti D. Green L. Guillemot S. Guiriec A. K. Harding T. Jogler G. Jóhannesson T. Kamae M. Kuss G. La Mura L. Latronico F. Longo F. Loparco P. Lubrano S. Maldera D. Malyshev A. Manfreda M. N. Mazziotta P. F. Michelson N. Mirabal W. Mitthumsiri T. Mizuno A. A. Moiseev M. E. Monzani A. Morselli I. V. Moskalenko M. Negro E. Nuss E. Orlando D. Paneque J. S. Perkins M. Pesce-Rollins F. Piron G. Pivato T. A. Porter G. Principe S. Rainò R. Rando M. Razzano A. Reimer O. Reimer C. Sgrò D. Simone E. J. Siskind F. Spada G. Spandre P. Spinelli H. Tajima J. B. Thayer L. Tibaldo D. F. Torres E. Troja M. Wood A. Worley G. Zaharijas S. Zimmer Department of Physical Sciences Hiroshima University Higashi-Hiroshima Hiroshima 739-8526 Japan Deutsches Elektronen Synchrotron DESY D-15738 Zeuthen Germany Department of Physics and Astronomy Clemson University Kinard Lab of Physics Clemson South Carolina 29634-0978 USA Santa Cruz Institute for Particle Physics Department of Physics and Department of Astronomy and Astrophysics University of California at Santa Cruz Santa Cruz California 95064 USA Università di Pisa and Istituto Nazionale di Fisica Nucleare Sezione di Pisa I-56127 Pisa Italy Istituto Nazionale di Fisica Nucleare Sezione di Trieste I-34127 Trieste Italy Dipartimento di Fisica Università di Trieste I-34127 Trieste Italy Istituto Nazionale di Fisica Nucleare Sezione di Padova I-35131 Padova Italy Dipartimento di Fisica e Astronomia “G. Galilei ” Università di Padova I-35131 Padova Italy Istituto Nazionale di Fisica Nucleare Sezione di Pisa I-56127 Pisa Italy W. W. Hansen Experimental Physics Laboratory Kavli Institute for Particle Astrophysics and Cosmology Department of Physics and SLAC National Accelerator Laboratory Stanford University Stanford California 94305 USA Istituto Nazionale di Fisica Nucleare Sezione di Torino I-10125 Torino Italy Dipartimento di Fisica Università degli Studi di Torino I-10125 Torino Italy NASA Goddard Space Flight Center Greenbelt Maryland 20771 USA Laboratoire Univers et Particules de Montpellier Université Montpellier CNRS/IN2P3 F-34095 Montpellier France Laboratoire Leprince-Ringuet École polytechnique CNRS/IN2P3 F-91128 Palaiseau France Dipartimento di Fisica “M. Merlin” dell’Università e del Politecnico di Bari I-70126 Bari Italy Istituto Nazionale di Fisica Nucleare Sezione di Bari I-70126 Bari Italy Agenzia Spaziale Italiana (ASI) Science Data Center I-00133 Roma Italy Istituto Nazionale di Fisica Nucleare Sezione di Perugia I-06123 Perugia Italy Dipartimento di Fisica Università degli Studi di Perugia I-06123 Perugia Italy College of Science

We present a measurement of the cosmic-ray electron+positron spectrum between 7 GeV and 2 TeV performed with almost seven years of data collected with the Fermi Large Area Telescope. We find that the spectrum is well fit by a broken power law with a break energy at about 50 GeV. Above 50 GeV, the spectrum is well described by a single power law with a spectral index of 3.07±0.02(stat+syst)±0.04(energy measurement). An exponential cutoff lower than 1.8 TeV is excluded at 95% CL.

关键词： Cosmic ray & astroparticle detectors Cosmic ray composition & spectra Cosmic ray sources Particle astrophysics

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A heuristic fuzzy algorithm bio-inspired by Evolution Strategies for energy forecasting problems

A heuristic fuzzy algorithm bio-inspired by Evolution Strate...

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IEEE International Conference on Fuzzy Systems (FUZZ-IEEE)

作者： Vitor N. Coelho Frederico G. Guimarães Agnaldo J. R. Reis Igor M. Coelho Bruno N. Coelho Marcone J. F. Souza Graduate Program in Electrical Engineering Universidade Federal de Minas Gerais Belo Horizonte MG Brazil Departament of Electrical Engineering Universidade Federal de Minas Gerais Belo Horizonte MG Brazil Department of Control Engineering and Automation Universidade Federal de Ouro Preto Ouro Preto MG Brazil Institute of Computing Universidade Federal Fluminense Niteri RJ Brazil Department of Computer Science Universidade Federal de Ouro Preto Ouro Preto MG Brazil

Improving the use of energy resources has been a great challenge in the last years. A new complex scenario involving a decentralized bidirectional communication between energy suppliers, distribution system and consumption is nowadays becoming reality. Sometimes cited as the largest and most complex machine ever built, Electric Grids (EG) are been transformed into Smart Grids (SG). Hence, the load forecasting problem has become more difficulty and more autonomous load predictors are needed in this new conjecture. In this paper a novel method, so-called MSES, bio-inspired by Evolution Strategies (ES) combined with Multi-Start (MS) procedure is described. This procedure is mainly based on a self-adaptive algorithm to calibrate the parameters of the fuzzy rules. MSES was implemented in C++ via OptFrame framework. Our main goal is to evaluate the performance of this algorithm in a grid environment. Real data from an electric utility have been used in order to test the proposed methodology. The obtained results are fully described and analyzed.

关键词： Forecasting Vectors Prediction algorithms Predictive models Training Standards Adaptation models

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GUGA: A tool for participatory cities

GUGA: A tool for participatory cities

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IEEE Symposium on Computers and Communications (ISCC)

作者： Luana Carine Schünke Luiz Paulo Luna de Oliveira Marta Becker Villamil Applied Computing Graduate Program University of Vale do Rio dos Sinos - Unisinos São Leopoldo RS Brazil Applied Computing Graduate Program University of Vale do Rio dos Sinos - Unisinos São Leopoldo Brazil

Participatory cities are those that allow the participation of citizens in the construction and improvement of their common daily life. In this work we present a tool for that participation, allowing the citizens to register the occurrences as well as take knowledge about the global geographic status of their city in on a variety of contexts (security, transit, etc.). However, a tool like that, fed by the people, certainly will deal with a large amount of information, distributed geographically. To accomplish that, a precise criterion for visualizing the resultant density distribution of occurrences must be used. In this paper, we also propose an automatic method for that visualization based on Voronoi Diagrams. The Voronoi polygons divide the region according to the concentration of occurrences. In this scheme, the area of each Voronoi polygon defines the density of the occurrences of the specific categories which are shown in the city map in color and transparency intensities for visualization. This can easily reveal the space distribution of important issues, in a variety of contexts such as criminality, commercial and industrial activities, drugs traffic, illumination concerns, and others.

关键词： Cities and towns Data visualization Registers Government Social network services Visualization Color

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Expert user discovery in a spontaneous social network an approach using knowledge retrieval

Expert user discovery in a spontaneous social network an app...

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International Conference on Computational Aspects of Social Networks, CASON

作者： Gustavo Freitas Cristiano da Costa Jorge Barbosa Rodrigo Righi Adenauer Yamin Applied Computing Graduate Program-PlPCA University of Vale do Rio dos Sinos Sao Leopoldo Brazil Graduate Program in Computer Science-PPGC Federal University of Pelotas Pelotas Brazil

Nowadays, we can observe that finding answers on social networks is a hard and time-consuming task. The main contribution of this article is the creation of a model and algorithm that allows users to find answers to their questions using a spontaneous social network called Mingle. This algorithm uses the Mingle ontology-based knowledge base to find expert users. To achieve this, two important steps are taken: Mingle ontology is updated to support user-oriented expertise and a detailed model is created for the given algorithm. This model was created considering other three similar applications and algorithms. Moreover, we used a semantic web framework. In the end, an evaluation using real-life scenarios is applied to evaluate if the created algorithm meets the initial goals.

关键词： Social network services

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Risk management in scientific research: A proposal guided in project management book of knowledge and Failure Mode and Effects Analysis

Risk management in scientific research: A proposal guided in...

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Frontiers in Education (FIE) Conference

作者： Pollyana Notargiacomo Mustaro Rogério Rossi Graduate Program in Electrical Engineering/School of Computing and Informatics Mackenzie Presbyterian University São Paulo Brazil Graduate Program in Electrical Engineering Mackenzie Presbyterian University São Paulo Brazil

ISBN: (纸本)9781467352598

The achievement of different university degrees (from graduate to the specialization, master's and doctoral) usually is related to the development and presentation of research results conducted by an Academic Advisor. However, their finalization or the results may be adversely affected by the lack of identification of risk that may present themselves during the process of construction and development of the research. To minimize these impacts, the present study was based on the alignment and adjustment of processes present in the Project Management Body of Knowledge (PMBoK), a specific guide that consolidates the best practices of project management from the Project Management Institute (PMI), and the use of Failure Mode and Effects Analysis (FMEA). From such elements and the identification of factors relevant to the educational institution involved and the processes related to the advisory and development of scientific research, it was sought to build a proposed risk analysis in the academic, named Academic Project Risk Management Plan (APRMP). This aims to contribute to the discussion and gathering information that can support the Advisor and the student at all stages of the research (planning, development and conclusion) that downside risks are avoided or minimized and that opportunities become clear and effective possibilities.

关键词： Risk management Proposals Educational institutions Monitoring Planning

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Using equivalence classes for testing programs for safety instrumented systems

Using equivalence classes for testing programs for safety in...

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2013 IEEE 18th International Conference on Emerging Technologies and Factory Automation, ETFA 2013

作者： De Vasconcelos Oliveira, Kézia Perkusich, Angelo Gorgônio, Kyller Costa Dias Da Silva, Leandro Martins, Aldenor Falcão Center of Electrical Engineering and Informatics Federal University of Campina Grande Campina Grande Parafba Brazil Computing Institute Federal University of Alagoas Maceió Alagoas Brazil Graduate Program in Electrical Engineering Federal University of Campina Grande Campina Grande Paraíba Brazil

ISBN: (纸本)9781479908622

The reliability on Safety Instrumented Systems (SIS) is critical for the safe operation of many industrial applications. In particular, SIS play an important role in oil and gas processing plants. SIS are responsible not only for the continuous operation of the plant, it also keeps the plant in a safe state, avoiding damages to the environment and minimizing risks to employees. Therefore, the correct behavior of such systems is an important goal to achieve when building industrial plants. Verification and testing of SIS programs is a very hard task to accomplish. This happens mainly for two reasons. First, testing the real system is very expensive and sometimes it may take a huge amount of time, weeks or even months. Second, those systems deal with a huge number of variables. It is not always possible for a human tester to check if all of them are correct when performing tests. Providing an automatic and formal testing approach for such systems is an important contribution for the development of such systems. In this work we introduce a new method for generating test cases for SIS programs running on programable Logic Controller (PLC). As we did on previous work, ISA 5.2 diagrams are used as specification of the systems, but now we are using a hardware-in-the-loop technique, and the target artifact is a software running on a PLC. To avoid the execution of redundant tests, we introduced a new test case generation algorithm that is based on equivalence classes. Finally, we discussed a study case in which our method is used to detect error, that were introduced on purpose, on a simple system. © 2013 IEEE.

关键词： Safety testing

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Search for extended sources in the galactic plane using 6 years of Fermi-Large area telescope pass 8 data above 10 GeV

arXiv

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arXiv 2017年

作者： Ackermann, M. Ajello, M. 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. Caragiulo, M. Caraveo, P.A. Castro, D. Cavazzuti, E. Cecchi, C. Charles, E. Chekhtman, A. Cheung, C.C. Chiaro, G. Ciprini, S. Cohen, J.M. Costantin, D. 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. Fegan, S.J. Ferrara, E.C. Franckowiak, A. Fukazawa, Y. Funk, S. Fusco, P. Gargano, F. Gasparrini, D. Giglietto, N. Giordano, F. Giroletti, M. Green, D. Grenier, I.A. Grondin, M.-H. Guillemot, L. Guiriec, S. Harding, A.K. Hays, E. Hewitt, J.W. Horan, D. Hou, X. Jóhannesson, G. Kamae, T. Kuss, M. la Mura, G. Larsson, S. Lemoine-Goumard, M. Li, J. Longo, F. Loparco, F. Lubrano, P. Magill, J.D. Maldera, S. Malyshev, D. Manfreda, A. Mazziotta, M.N. Michelson, P.F. Mitthumsiri, W. Mizuno, T. Monzani, M.E. Morselli, A. Moskalenko, I.V. Negro, M. Nuss, E. Ohsugi, T. Omodei, N. Orienti, M. Orlando, E. Ormes, J.F. Paliya, V.S. Paneque, D. Perkins, J.S. Persic, M. Pesce-Rollins, M. Petrosian, V. Piron, F. Porter, T.A. Principe, G. Rainò, S. Rando, R. Razzano, M. Razzaque, S. Reimer, A. Reimer, O. Reposeur, T. Sgrò, C. Simone, D. Siskind, E.J. Spada, F. Spandre, G. Spinelli, P. Suson, D.J. Tak, D. Thayer, J.B. Thompson, D.J. Torres, D.F. Tosti, G. Troja, E. Vianello, G. Wood, K.S. Wood, M. Deutsches Elektronen Synchrotron DESY ZeuthenD-15738 Germany Department of Physics and Astronomy Clemson University Kinard Lab of Physics ClemsonSC29634-0978 United States Università di Pisa Istituto Nazionale di Fisica Nucleare Sezione di Pisa PisaI-56127 Italy Laboratoire AIM CEA-IRFU CNRS Université Paris Diderot Service d’Astrophysique CEA Saclay Gif sur YvetteF-91191 France Istituto Nazionale di Fisica Nucleare Sezione di Trieste TriesteI-34127 Italy Dipartimento di Fisica Università di Trieste TriesteI-34127 Italy Istituto Nazionale di Fisica Nucleare Sezione di Padova PadovaI-35131 Italy Dipartimento di Fisica e Astronomia "G. Galilei" Università di Padova PadovaI-35131 Italy Istituto Nazionale di Fisica Nucleare Sezione di Pisa PisaI-56127 Italy Istituto Nazionale di Fisica Nucleare Sezione di Bari BariI-70126 Italy W. W. Hansen Experimental Physics Laboratory Kavli Institute for Particle Astrophysics and Cosmology Department of Physics SLAC National Accelerator Laboratory Stanford University StanfordCA94305 United States Istituto Nazionale di Fisica Nucleare Sezione di Torino TorinoI-10125 Italy Dipartimento di Fisica Università degli Studi di Torino TorinoI-10125 Italy NASA Goddard Space Flight Center GreenbeltMD20771 United States Laboratoire Univers et Particules de Montpellier Université Montpellier CNRS/IN2P3 MontpellierF-34095 France Laboratoire Leprince-Ringuet École polytechnique CNRS/IN2P3 PalaiseauF-91128 France Dipartimento di Fisica "M. Merlin" dell’Università e del Politecnico di Bari BariI-70126 Italy INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica Milano via E. Bassini 15 MilanoI-20133 Italy Science Data Center RomaI-00133 Italy Istituto Nazionale di Fisica Nucleare Sezione di Perugia PerugiaI-06123 Italy Dipartimento di Fisica Università degli Studi di Perugia PerugiaI-06123 Italy College of Science George Mason University Fairfax VA22030 United States Naval Research Laboratory Washi

The spatial extension of a γ-ray source is an essential ingredient to determine its spectral properties as well as its potential multi-wavelength counterpart. The capability to spatially resolve γ-ray sources is greatly improved by the newly delivered Fermi-Large Area Telescope (LAT) Pass 8 event-level analysis which provides a greater acceptance and an improved point spread function, two crucial factors for the detection of extended sources. Here, we present a complete search for extended sources located within 7◦ from the Galactic plane, using 6 years of Fermi-LAT data above 10 GeV. We find 46 extended sources and provide their morphological and spectral characteristics. This constitutes the first catalog of hard Fermi-LAT extended sources, named the Fermi Galactic Extended Source Catalog, which allows a thorough study of the properties of the Galactic plane in the sub-TeV domain. Copyright © 2017, The Authors. All rights reserved.

关键词： Gamma rays

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Analyzing Performance of the Parallel-based Fractal Image Compression Problem on Multicore Systems

Analyzing Performance of the Parallel-based Fractal Image Co...

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The 2013 AASRI Conference on Parallel and Distributed computing and Systems(DCS 2013)

作者： Roberto de Quadros Gomes Vladimir Guerreiro Rodrigo da Rosa Righi Luiz Gonzaga da Silveira Jr. JinyoungYang Applied Computing Graduate Program-PIPCA-UNISINOS-Unisinos Avenue 950 Korean Advanced Institute of Science and Technology-KAIST-291 Daehak-ro

Both the size and the resolution of images always were key topics in the graphical computing ***,they become more and more relevant in the big data *** can observe that often a huge amount of data is exchanged by medium/low bandwidth networks or yet,they need to be stored on devices with limited space of *** this context,the present paper shows the use of the Fractal method for image *** is a lossy method known by providing higher indexes of file reduction through a highly time consuming *** this way,we developed a model of parallel application for exploiting the power of multiprocessor architectures in order to get the Fractal method advantages in a feasible *** evaluation was done with different-sized images as well as by using two types of machines,one with two and another with four *** results demonstrated that both the speedup and efficiency are highly dependent of the number of *** emphasized that a large number of threads does not always represent a better performance.

关键词： Parallel programing Fractal Coding Multicore architectures Parallel modeling Threads Performance analysis

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Diffusion suppression in gel dosimetry by addition of nanoclay

Diffusion suppression in gel dosimetry by addition of nanocl...

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World Congress on Medical Physics and Biomedical Engineering

作者： Maeyama, T. Fukunishi, N. Ishikawa, K.L. Fukasaku, K. Furuta, T. Takagi, S. Noda, S. Himeno, R. RIKEN Nishina Center for Accelerator-Based Science Wako Japan RIKEN Computational Science Research Program Wako Japan University of Tokyo Department of Nuclear Engineering and Management Graduate School of Engineering Tokyo Japan University of Tokyo Photon Science Center Graduate School of Engineering Tokyo Japan Himon'ya Hospital Department of Neurosurgery Tokyo Japan University of Tokyo Department of Mechanical Engineering Graduate School of Engineering Tokyo Japan RIKEN Advanced Center for Computing and Communication Wako Japan

ISBN: (纸本)9783642293047

This paper reports diffusion suppression in gel dosimetery by using nanocomposite gel. A Fricke xylenol gel (FXG) and a dichromate gel (DCG) were selected for adding a small amount of nanoclay (Laponite XLG). The diffusion coefficient and T1 distribution were evaluated by irradiating the gel dosimeter with a heavy ion beam. As a result, these gels showed improvement in the diffusion coefficient. In particular, by addition of the clay, the DCG exhibited diffusion-free characteristics. Moreover, it exhibited high stability after irradiation. © 2013 Springer-Verlag.

关键词： Nanocomposites

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OBSERVATIONS OF M31 AND M33 WITH THE FERMI LARGE AREA TELESCOPE: A GALACTIC CENTER EXCESS IN ANDROMEDA?

arXiv

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arXiv 2017年

作者： 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. 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. Deutsches Elektronen Synchrotron DESY ZeuthenD-15738 Germany Department of Physics and Astronomy Clemson University Kinard Lab of Physics ClemsonSC29634-0978 United States Los Alamos National Laboratory Los AlamosNM87545 United States Università di Pisa Istituto Nazionale di Fisica Nucleare Sezione di Pisa PisaI-56127 Italy Laboratoire AIM CEA-IRFU CNRS Université Paris Diderot Service d’Astrophysique CEA Saclay Gif sur YvetteF-91191 France Istituto Nazionale di Fisica Nucleare Sezione di Trieste TriesteI-34127 Italy Dipartimento di Fisica Università di Trieste TriesteI-34127 Italy Istituto Nazionale di Fisica Nucleare Sezione di Padova PadovaI-35131 Italy Dipartimento di Fisica e Astronomia "G. Galilei" Università di Padova PadovaI-35131 Italy Istituto Nazionale di Fisica Nucleare Sezione di Pisa PisaI-56127 Italy Istituto Nazionale di Fisica Nucleare Sezione di Bari BariI-70126 Italy W. W. Hansen Experimental Physics Laboratory Kavli Institute for Particle Astrophysics and Cosmology Department of Physics SLAC National Accelerator Laboratory Stanford University StanfordCA94305 United States Istituto Nazionale di Fisica Nucleare Sezione di Torino TorinoI-10125 Italy Dipartimento di Fisica Università degli Studi di Torino TorinoI-10125 Italy NASA Goddard Space Flight Center GreenbeltMD20771 United States Laboratoire Univers et Particules de Montpellier Université Montpellier CNRS/IN2P3 MontpellierF-34095 France Laboratoire Leprince-Ringuet École polytechnique CNRS/IN2P3 PalaiseauF-91128 France Santa Cruz Institute for Particle Physics Department of Physics Department of Astronomy and Astrophysics University of California at Santa Cruz Santa CruzCA95064 United States Dipartimento di Fisica "M. Merlin" dell’Università e del Politecnico di Bari BariI-70126 Italy INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica Milano via E. Bassini 15 MilanoI-20133 Italy Science Data Center RomaI-00133 Italy Istituto Nazionale di Fi

The Fermi Large Area Telescope (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 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 upper limit of 2.0×10−12 erg cm−2 s−1 on the 0.1−100 GeV energy flux (95% confidence level). This revised upper limit 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 10σ. Its spectrum is consistent with a power law with photon index Γ = 2.4±0.1stat+syst and a 0.1−100 GeV energy flux of (5.6±0.6stat+syst)×10−12 erg cm−2 s−1. M31 is detected to be extended with a 4σ significance. The spatial distribution of the emission is consistent with a uniform-brightness disk with a radius of 0◦.4 and no offset from the center of the galaxy, 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 of the galaxy or extend far from it. The gamma-ray signal is not correlated with regions rich in gas or star-formation activity, which suggests 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

关键词： Galaxies

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