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Unresolved Gamma-Ray Sky through its Angular Power Spectrum

Physical Review Letters 2018年第24期121卷 241101-241101页

作者： M. Ackermann M. Ajello L. Baldini J. Ballet G. Barbiellini D. Bastieri R. Bellazzini E. Bissaldi R. D. Blandford R. Bonino E. Bottacini J. Bregeon P. Bruel R. Buehler E. Burns S. Buson R. A. Cameron R. Caputo P. A. Caraveo E. Cavazzuti S. Chen G. Chiaro S. Ciprini D. Costantin A. Cuoco S. Cutini F. D’Ammando P. de la Torre Luque F. de Palma A. Desai S. W. Digel N. Di Lalla M. Di Mauro L. Di Venere F. Fana Dirirsa C. Favuzzi A. Franckowiak Y. Fukazawa S. Funk P. Fusco F. Gargano D. Gasparrini N. Giglietto F. Giordano M. Giroletti D. Green I. A. Grenier L. Guillemot S. Guiriec D. Horan G. Jóhannesson M. Kuss S. Larsson L. Latronico J. Li I. Liodakis F. Longo F. Loparco P. Lubrano J. D. Magill S. Maldera D. Malyshev A. Manfreda M. N. Mazziotta I. Mereu P. F. Michelson W. Mitthumsiri T. Mizuno M. E. Monzani A. Morselli I. V. Moskalenko M. Negro E. Nuss M. Orienti E. Orlando M. Palatiello V. S. Paliya D. Paneque M. Persic M. Pesce-Rollins V. Petrosian F. Piron T. A. Porter G. Principe S. Rainò R. Rando M. Razzano S. Razzaque A. Reimer O. Reimer D. Serini C. Sgrò E. J. Siskind G. Spandre P. Spinelli D. J. Suson H. Tajima M. Takahashi J. B. Thayer L. Tibaldo D. F. Torres E. Troja T. M. Venters G. Vianello K. Wood M. Yassine G. Zaharijas S. Ammazzalorso N. Fornengo M. Regis 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 Università di Pisa and Istituto Nazionale di Fisica Nucleare Sezione di Pisa I-56127 Pisa Italy Laboratoire AIM CEA-IRFU/CNRS/Université Paris Diderot Service d’Astrophysique CEA Saclay F-91191 Gif sur Yvette France 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 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 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 Department of Physics and Astronomy University of Padova Vicolo Osservatorio 3 I-35122 Padova Italy 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 NASA Goddard Space Flight Center Greenbelt Maryland 20771 USA Center for Research and Exploration in Space Science and Technology (CRESST) and NASA Goddard Space Flight Center Greenbelt Maryland 20771 USA INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica Milano via E. Bassini 15 I-20133 Milano Italy Italian Space Agency Via del Politecnico snc 00133 Roma Ita

The gamma-ray sky has been observed with unprecedented accuracy in the last decade by the Fermi -large area telescope (LAT), allowing us to resolve and understand the high-energy Universe. The nature of the remaining unresolved emission [unresolved gamma-ray background (UGRB)] below the LAT source detection threshold can be uncovered by characterizing the amplitude and angular scale of the UGRB fluctuation field. This Letter presents a measurement of the UGRB autocorrelation angular power spectrum based on eight years of Fermi-LAT Pass 8 data products. The analysis is designed to be robust against contamination from resolved sources and noise systematics. The sensitivity to subthreshold sources is greatly enhanced with respect to previous measurements. We find evidence (with ∼3.7σ significance) that the scenario in which two classes of sources contribute to the UGRB signal is favored over a single class. A double power law with exponential cutoff can explain the anisotropy energy spectrum well, with photon indices of the two populations being 2.55±0.23 and 1.86±0.15.

关键词： Gamma ray astronomy

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A Data Hiding Scheme Based on Lagrange Interpolation Algorithm and Multi-clouds

A Data Hiding Scheme Based on Lagrange Interpolation Algorit...

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International Symposium on Parallel Architectures, Algorithms and Programming (PAAP)

作者： Yu Jin Yadan Wang Wei Xia Li Deng Heng He Hubei Province Key Laboratory of Intelligent Information Processing and Real-time Industrial Wuhan China Department of Computer Science and Technology Wuhan University of Science and Technology

The use of cloud storage services has increased rapidly in many organizations. However, the security of data stored in the cloud still remains major concerns. Due to risks of service availability failure and the possibility of malicious insiders in the single cloud, researches about "multi-clouds" have emerged recently. Recent researches that are related to multi-clouds have some limitations. For instance, Redundant Array of Cloud Storage (RACS) does not ensure data confidentiality. The performance of system is low in DEPSKY and so on. This paper presents a data hiding scheme that is based on Lagrange interpolation algorithm and multi-clouds. This scheme addresses data availability, data confidentiality and vendor lock-in issue in cloud storage services through the erasure codes and Lagrange interpolation algorithm instead of encryption to store data on diverse clouds. The performance analysis was done through experiences. We observed that our scheme improved the performance for the response times of data uploaded and downloaded.

关键词： Cloud computing Interpolation Reed-Solomon codes Encoding Encryption

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Search for gamma-ray emission from local primordial black holes with the Fermi large area telescope

arXiv

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arXiv 2018年

作者： Ackermann, M. Atwood, W.B. Baldini, L. Ballet, J. Barbiellini, G. Bastieri, D. Bellazzini, R. Berenji, B. Bissaldi, E. Blandford, R.D. Bloom, E.D. Bonino, R. Bottacini, E. Bregeon, J. Bruel, P. Buehler, R. Cameron, R.A. Caputo, R. Caraveo, P.A. Cavazzuti, E. Charles, E. Chekhtman, A. Cheung, C.C. Chiaro, G. Ciprini, S. Cohen-Tanugi, J. Conrad, J. Costantin, D. D’Ammando, F. de Palma, F. Digel, S.W. Di Lalla, N. Di Mauro, M. Di Venere, L. Favuzzi, C. Fegan, S.J. Focke, W.B. Franckowiak, A. Fukazawa, Y. Funk, S. Fusco, P. Gargano, F. Gasparrini, D. Giglietto, N. Giordano, F. Giroletti, M. Green, D. Grenier, I.A. Guillemot, L. Guiriec, S. Horan, D. Jóhannesson, G. Johnson, C. Kensei, S. Kocevski, D. Kuss, M. Larsson, S. Latronico, L. Li, J. Longo, F. Loparco, F. Lovellette, M.N. Lubrano, P. Magill, J.D. Maldera, S. Malyshev, D. Manfreda, A. Mazziotta, M.N. McEnery, J.E. Meyer, M. Michelson, P.F. Mitthumsiri, W. Mizuno, T. Monzani, M.E. Moretti, E. Morselli, A. Moskalenko, I.V. Negro, M. Nuss, E. Ojha, R. Omodei, N. Orienti, M. Orlando, E. Ormes, J.F. Palatiello, M. Paliya, V.S. Paneque, D. Persic, M. Pesce-Rollins, M. Piron, F. Principe, G. Rainò, S. Rando, R. Razzano, M. Razzaque, S. Reimer, A. Reimer, O. Ritz, S. Sánchez-Conde, M. Sgrò, C. Siskind, E.J. Spada, F. Spandre, G. Spinelli, P. Suson, D.J. Tajima, H. Thayer, J.G. Thayer, J.B. Torres, D.F. Tosti, G. Troja, E. Valverde, J. Vianello, G. Wood, K. Wood, M. Zaharijas, G. Deutsches Elektronen Synchrotron DESY ZeuthenD-15738 Germany Santa Cruz Institute for Particle Physics Department of Physics Department of Astronomy and Astrophysics University of California at Santa Cruz Santa CruzCA95064 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 California State University Los Angeles Department of Physics and Astronomy Los AngelesCA90032 United States Dipartimento di Fisica "M. Merlin" dell’Università e del Politecnico di Bari BariI-70126 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 Laboratoire Univers et Particules de Montpellier Université Montpellier CNRS/IN2P3 MontpellierF-34095 France Laboratoire Leprince-Ringuet École polytechnique CNRS/IN2P3 PalaiseauF-91128 France NASA Goddard Space Flight Center GreenbeltMD20771 United States INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica Milano via E. Bassini 15 MilanoI-20133 Italy Italian Space Agency Via del Politecnico snc Roma00133 Italy College of Science George Mason University Fairfax Naval Researc

Black holes with masses below approximately 1015 g are expected to emit gamma rays with energies above a few tens of MeV, which can be detected by the Fermi Large Area Telescope (LAT). Although black holes with these masses cannot be formed as a result of stellar evolution, they may have formed in the early Universe and are therefore called Primordial Black Holes (PBHs). Previous searches for PBHs have focused on either short timescale bursts or the contribution of PBHs to the isotropic gamma-ray emission. We show that, in case of individual PBHs, the Fermi LAT is most sensitive to PBHs with temperatures above approximately 16 GeV and masses 6×1011 g, which it can detect out to a distance of about 0.03 pc. These PBHs have a remaining lifetime of months to years at the start of the Fermi mission. They would appear as potentially moving point sources with gamma-ray emission that becomes spectrally harder and brighter with time until the PBH completely evaporates. In this paper, we develop a new algorithm to detect the proper motion of a gamma-ray point sources, and apply it to 318 unassociated point sources at high galactic latitude in the third Fermi-LAT source catalog (3FGL). None of unassociated point sources with spectra consistent with PBH evaporation show significant proper motion. Using the non-detection of PBH candidates, we derive a 99% confidence limit on PBH evaporation rate in the vicinity of the Earth ρPBH 3 pc−3yr−1. This limit is similar to the limits obtained with ground-based gamma-ray observatories. Copyright © 2018, The Authors. All rights reserved.

关键词： Gamma rays

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Risk Management Using Big real time Data

Risk Management Using Big Real Time Data

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IEEE International Conference on Cloud computing Technology and science (CloudCom)

作者： Jie Cheng Chunming Rong Huijuan Ye Xianghan Zheng Department of Electrical Engineering and Computer Science Risk Management Using Big Real Time Data Department of Computer Science and Electronic Engineering University of Stavanger Stavanger Norway College of Mathematics and Computer Science Fuzhou University Fuzhou China Fujian Key Laboratory of Network Computing and Intelligent Information Processing Fuzhou China

Adding to societal changes today, are the miscellaneous big data produced in different fields. Coupled with these data is the appearance of risk management. Admittedly, to predict future trend by using these data is conducive to make everything more efficient and easy. Now, no matter companies or individuals, they increasingly focus on identifying risks and managing them before risks. Effective risk management will lead them to deal with potential problems. This thesis focuses on risk management of flight delay area using big real time data. It proposes two different prediction models, one is called General Long Term Departure Prediction Model and the other is named as Improved real time Arrival Prediction Model. By studying the main factors lead to flight delay, this thesis takes weather, carrier, National Aviation System, security and previous late aircraft as analysis factors. By utilizing our models can do not only long time but also short term flight delay predictions. The results demonstrate goodness of fit. Besides the theory part, it also presents a practical and beautiful web application for real time flight arrival prediction based on our second model.

关键词： Delays Biological system modeling Meteorology Atmospheric modeling Predictive models Airports Splines (mathematics)

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Exploiting Job Response-time Information in the Co-Design of real-time Control Systems

Exploiting Job Response-Time Information in the Co-Design of...

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IEEE International Conference on Embedded and real-time computing Systems and Applications (RTCSA)

作者： Yang Xu Karl-Erik Årzén Anton Cervin Enrico Bini Bogdan Tanasa Department of Automatic Control Lund University Sweden Scuola Superiore Sant'Anna Real-Time Systems Laboratory Italy Department of Computer and Information Science Linköping University Sweden

We consider a real-time system of multiple tasks, each task having a plant to control. The overall quadratic control cost is to be optimized. We exploit the periodicity of the task response time, which corresponds to a periodic delay pattern in the feedback control loop. Perturbed periods are used as a tool to find a finite hyper period. We present an analytical procedure to design a periodic linear-quadratic-Gaussian (LQG) controller for tasks with fixed execution times as well as a numerical solution to the periodic -- stochastic LQG problem for tasks with variable execution times. The controllers are evaluated using simulations in real-time scheduling and control co-design examples.

关键词： Delays real-time systems Control design time factors Mathematical model Numerical models Cost function

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An efficient topology-based algorithm for transient analysis of power grid 11th

An efficient topology-based algorithm for transient analysis...

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11th International Conference on Intelligent computing, ICIC 2015

作者： Yang, Lan Wang, Jingbin Azevedo, Lorenzo Wang, Jim Jing-Yan School of Computer Science and Information Engineering Chongqing Technology and Business University Chongqing400067 China Tianjin Key Laboratory of Cognitive Computing and Application Tianjin University Tianjin300072 China National Time Service Center Chinese Academy of Sciences Xi’an710600 China Provincial Key Laboratory for Computer Information Processing Technology Soochow University Suzhou215006 China Computer Science Department University of Säo Paulo Säo Paulo SP05508-070 Brazil Thuwal23955-6900 Saudi Arabia

ISBN: (纸本)9783319221793

In the design flow of integrated circuits, chip-level verification is an important step that sanity checks the performance is as expected. Power grid verification is one of the most expensive and time-consuming steps of chip-level verification, due to its extremely large size. Efficient power grid analysis technology is highly demanded as it saves computing resources and enables faster iteration. In this paper, a topology-base power grid transient analysis algorithm is proposed. Nodal analysis is adopted to analyze the topology which is mathematically equivalent to iteratively solving a positive semi-definite linear equation. The convergence of the method is proved. © Springer International Publishing Switzerland 2015.

关键词： Topology

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Protein 3D Features and surface modeling research

Protein 3D Features and surface modeling research

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2015 3rd International Conference on Machinery,Materials and Information Technology Applications(ICMMITA 2015)

作者： Huayong Yang Xiaoli Lin Information and Engineering Department of City College Wuhan University of Science and Technology Hubei Key Laboratory of Intelligent Information Processing and Real-time Industrial System School of Computer Science and Technology Wuhan University of Science and Technology

In the twenty-first century, the life science has been studied from the genome research into the structure and function of the structure, which can further reveal the mystery of life. In this paper, it takes the relationship between protein structure and its function as the breakthrough point, with the aid of introducing the protein molecular structure database, analyzing the application of intelligent computing method in the prediction of protein structure. Moreover, by setting up the 3D model of protein molecules, so as to realize the detection of protein 3D features.

关键词： protein molecular intelligent computing 3D features

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Unresolved gamma-ray sky through its angular power spectrum

arXiv

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arXiv 2018年

作者： Ackermann, M. Ajello, M. Baldini, L. Ballet, J. Barbiellini, G. Bastieri, D. Bellazzini, R. Bissaldi, E. Blandford, R.D. Bonino, R. Bottacini, E. Bregeon, J. Bruel, P. Buehler, R. Burns, E. Buson, S. Cameron, R.A. Caputo, R. Caraveo, P.A. Cavazzuti, E. Chen, S. Chiaro, G. Ciprini, S. Costantin, D. Cuoco, A. Cutini, S. D’Ammando, F. de la Torre Luque, P. de Palma, F. Desai, A. Digel, S.W. Di Lalla, N. Di Mauro, M. Di Venere, L. Fana Dirirsa, F. Favuzzi, C. Franckowiak, A. Fukazawa, Y. Funk, S. Fusco, P. Gargano, F. Gasparrini, D. Giglietto, N. Giordano, F. Giroletti, M. Green, D. Grenier, I.A. Guillemot, L. Guiriec, S. Horan, D. Jóhannesson, G. Kuss, M. Larsson, S. Latronico, L. Li, J. Liodakis, I. Longo, F. Loparco, F. Lubrano, P. Magill, J.D. Maldera, S. Malyshev, D. Manfreda, A. Mazziotta, M.N. Mereu, I. Michelson, P.F. Mitthumsiri, W. Mizuno, T. Monzani, M.E. Morselli, A. Moskalenko, I.V. Negro, M. Nuss, E. Orienti, M. Orlando, E. Palatiello, M. Paliya, V.S. Paneque, D. 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. Serini, D. Sgrò, C. Siskind, E.J. Spandre, G. Spinelli, P. Suson, D.J. Tajima, H. Takahashi, M. Thayer, J.B. Tibaldo, L. Torres, D.F. Troja, E. Venters, T.M. Vianello, G. Wood, K. Yassine, M. Zaharijas, G. Ammazzalorso, S. Fornengo, N. Regis, 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 Dipartimento di Fisica "M. Merlin" dell’Università e del Politecnico di Bari BariI-70126 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 Department of Physics and Astronomy University of Padova Vicolo Osservatorio 3 PadovaI-35122 Italy Laboratoire Univers et Particules de Montpellier Université Montpellier CNRS/IN2P3 MontpellierF-34095 France Laboratoire Leprince-Ringuet École polytechnique CNRS/IN2P3 PalaiseauF-91128 France NASA Goddard Space Flight Center GreenbeltMD20771 United States NASA Postdoctoral Program Fellow United States NASA Goddard Space Flight Center GreenbeltMD20771 United States INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica Milano via E. Bassini 15 MilanoI-20133 Italy Italian Space Agency Via del Politecnico snc Roma00133 Italy Space Science Data Center -

The gamma-ray sky has been observed with unprecedented accuracy in the last decade by the Fermi large area telescope (LAT), allowing us to resolve and understand the high-energy Universe. The nature of the remaining unresolved emission (unresolved gamma-ray background, UGRB) below the LAT source detection threshold can be uncovered by characterizing the amplitude and angular scale of the UGRB fluctuation field. This work presents a measurement of the UGRB autocorrelation angular power spectrum based on eight years of Fermi LAT Pass 8 data products. The analysis is designed to be robust against contamination from resolved sources and noise systematics. The sensitivity to subthreshold sources is greatly enhanced with respect to previous measurements. We find evidence (with ∼ 3.7σ significance) that the scenario in which two classes of sources contribute to the UGRB signal is favored over a single class. A double power law with exponential cutoff can explain the anisotropy energy spectrum well, with photon indices of the two populations being 2.55 ± 0.23 and 1.86 ± 0.15. Copyright © 2018, The Authors. All rights reserved.

关键词： Gamma rays

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Search for spatial extension in high-latitude sources detected by the fermi large area telescope

arXiv

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arXiv 2018年

作者： Ackermann, M. Ajello, M. Baldini, L. Ballet, J. Barbiellini, G. Bastieri, D. Bellazzini, R. Bissaldi, E. Blandford, R.D. Bloom, E.D. Bonino, R. Bottacini, E. Brandt, T.J. Bregeon, J. Bruel, P. Buehler, R. Cameron, R.A. Caputo, R. Caraveo, P.A. Castro, D. Cavazzuti, E. Charles, E. Cheung, C.C. Chiaro, G. Ciprini, S. Cohen-Tanugi, J. Costantin, D. Cutini, S. D'Ammando, F. de Palma, F. Desai, A. Di Lalla, N. Di Mauro, M. Di Venere, L. Favuzzi, C. Finke, J. Franckowiak, A. Fukazawa, Y. Funk, S. Fusco, P. Gargano, F. Gasparrini, D. Giglietto, N. Giordano, F. Giroletti, M. Green, D. Grenier, I.A. Guillemot, L. Guiriec, S. Hays, E. Hewitt, J.W. Horan, D. Jóhannesson, G. Kensei, S. Kuss, M. Larsson, S. Latronico, L. Lemoine-Goumard, M. Li, J. Longo, F. Loparco, F. Lovellette, M.N. Lubrano, P. Magill, J.D. Maldera, S. Manfreda, A. Mazziotta, M.N. McEnery, J.E. Meyer, M. Mizuno, T. Monzani, M.E. Morselli, A. Moskalenko, I.V. Negro, M. Nuss, E. Omodei, N. Orienti, M. Orlando, E. Ormes, J.F. Palatiello, M. Paliya, V.S. Paneque, D. Perkins, J.S. Persic, M. Pesce-Rollins, M. Piron, F. Porter, T.A. Principe, G. Rainó, S. Rando, R. Rani, B. Razzaque, S. Reimer, A. Reimer, O. Reposeur, T. Sgró, C. Siskind, E.J. Spandre, G. Spinelli, P. Suson, D.J. Tajima, H. Thayer, J.B. Tibaldo, L. Torres, D.F. Tosti, G. Valverde, J. Venters, T.M. Vogel, M. Wood, K. Wood, M. Zaharijas, G. Biteau, J. Deutsches Elektronen Synchrotron DESY ZeuthenD-15738 Germany Department of Physics and Astronomy Clemson University Kinard Lab of Physics ClemsonSC29634-0978 United States Universita di Pisa Istituto Nazionale di Fisica Nucleare Sezione di Pisa PisaI-56127 Italy Laboratoire AIM CEA-IRFU/CNRS/Universite 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 Universita di Trieste TriesteI-34127 Italy Istituto Nazionale di Fisica Nucleare Sezione di Padova PadovaI-35131 Italy Dipartimento di Fisica e Astronomia "G. Galilei" Universita di Padova PadovaI-35131 Italy Istituto Nazionale di Fisica Nucleare Sezione di Pisa PisaI-56127 Italy Dipartimento di Fisica 'M. Merlin" dell'Universita e del Politecnico di Bari BariI-70126 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 Universita degli Studi di Torino TorinoI-10125 Italy Department of Physics and Astronomy University of Padova Vicolo Osservatorio 3 PadovaI-35122 Italy NASA Goddard Space Flight Center GreenbeltMD20771 United States Laboratoire Univers et Particules de Montpellier Universite Montpellier CNRS/IN2P3 MontpellierF-34095 France Laboratoire Leprince-Ringuet Ecole polytechnique CNRS/IN2P3 PalaiseauF-91128 France NASA Goddard Space Flight Center GreenbeltMD20771 United States INAF-Istituto di Astrosica Spaziale e Fisica Cosmica Milano via E. Bassini 15 MilanoI-20133 Italy Harvard-Smithsonian Center for Astrophysics CambridgeMA02138 United States Italian Space Agency Via del Politecnico snc Roma00133 Italy S

We present a search for spatial extension in high-latitude (jbj > 5°) sources in recent Fermi point source catalogs. The result is the Fermi High-Latitude Extended Sources Catalog, which provides source extensions (or upper limits thereof) and likelihood profiles for a suite of tested source morphologies. We find 24 extended sources, 19 of which were not previously characterized as extended. These include sources that are potentially associated with supernova remnants and star forming regions. We also found extended -ray emission in the vicinity of the Cen A radio lobes and|at GeV energies for the first time|spatially coincident with the radio emission of the SNR CTA 1, as well as from the Crab Nebula. We also searched for halos around active galactic nuclei, which are predicted from electromagnetic cascades that are induced by the e+e- pairs that are deected in intergalactic magnetic fields. These are produced when -rays interact with background radiation fields. We do not find evidence for extension in individual sources or in stacked source samples. This enables us to place limits on the ux of the extended source components, which are then used to constrain the intergalactic magnetic field a coherence length λ 10 kpc, even when conservative assumptions on the source duty cycle are made. This improves previous limits by several orders of magnitude. Copyright © 2018, The Authors. All rights reserved.

关键词： Magnetic fields

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Search for Cosmic-Ray Electron and Positron Anisotropies with Seven Years of Fermi Large Area Telescope Data

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Physical Review Letters 2017年第9期118卷 091103-091103页

作者： S. Abdollahi M. Ackermann M. Ajello A. Albert W. B. Atwood L. Baldini G. Barbiellini R. Bellazzini E. Bissaldi E. D. Bloom R. Bonino E. Bottacini T. J. Brandt P. Bruel S. Buson M. Caragiulo E. Cavazzuti A. Chekhtman S. Ciprini 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 B. Donaggio P. S. Drell C. Favuzzi W. B. Focke Y. Fukazawa S. Funk P. Fusco F. Gargano D. Gasparrini N. Giglietto F. Giordano M. Giroletti D. Green S. Guiriec A. K. Harding T. Jogler G. Jóhannesson T. Kamae M. Kuss S. Larsson L. Latronico J. Li F. Longo F. Loparco P. Lubrano J. D. Magill D. Malyshev A. Manfreda M. N. Mazziotta M. Meehan P. F. Michelson W. Mitthumsiri T. Mizuno A. A. Moiseev M. E. Monzani A. Morselli M. Negro E. Nuss T. Ohsugi N. Omodei D. Paneque J. S. Perkins M. Pesce-Rollins F. Piron G. Pivato 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 A. W. Strong H. Tajima J. B. Thayer D. F. Torres E. Troja J. Vandenbroucke 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 Los Alamos National Laboratory Los Alamos New Mexico 87545 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 Dipartimento di Fisica “Enrico Fermi” dell’Università di Pisa I-56126 Pisa Italy 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 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 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 Leprince-Ringuet École polytechnique CNRS/IN2P3 F-91128 Palaiseau France Agenzia Spaziale Italiana (ASI) Science Data Center I-00133 Roma Italy College of Science George Mason University Fairfax Virginia 22030 USA resident at Naval Research Laboratory Washington DC 20375 USA Istituto Nazionale di Fisica Nucleare Sezione di Perugia I-06123 Perugia Italy Institute for Theoretical Particle Physics and Cosmology (TTK) RWTH Aachen University D-52056 Aachen Germany INAF Istituto di Radioastronomia I-40129 Bologna Italy Dipartimento di Astronomia Un

The Large Area Telescope on board the Fermi Gamma-ray Space Telescope has collected the largest ever sample of high-energy cosmic-ray electron and positron events since the beginning of its operation. Potential anisotropies in the arrival directions of cosmic-ray electrons or positrons could be a signature of the presence of nearby sources. We use almost seven years of data with energies above 42 GeV processed with the Pass 8 reconstruction. The present data sample can probe dipole anisotropies down to a level of 10−3. We take into account systematic effects that could mimic true anisotropies at this level. We present a detailed study of the event selection optimization of the cosmic-ray electrons and positrons to be used for anisotropy searches. Since no significant anisotropies have been detected on any angular scale, we present upper limits on the dipole anisotropy. The present constraints are among the strongest to date probing the presence of nearby young and middle-aged sources.

关键词： Cosmic ray & astroparticle detectors Cosmic ray propagation Cosmic ray sources Cosmological parameters

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