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arXiv 2017年

作者： Lin, Liang Wang, Keze Meng, Deyu Zuo, Wangmeng Zhang, Lei School of Data and Computer Science Sun Yat-sen University Guangzhou China Engineering Research Center Advanced Computing Engineering Software of Ministry of Education China School of Mathematics and Statistics Ministry of Education Key Lab of Intelligent Networks and Network Security Xi'an Jiaotong University China School of Computer Science and Technology Harbin Institute of Technology Harbin China Dept. of Computing Hong Kong Polytechnic University Hong Kong

This paper aims to develop a novel cost-effective framework for face identification, which progressively maintains a batch of classifiers with the increasing face images of different individuals. By naturally combining two recently rising techniques: active learning (AL) and self-paced learning (SPL), our framework is capable of automatically annotating new instances and incorporating them into training under weak expert recertification. We first initialize the classifier using a few annotated samples for each individual, and extract image features using the convolutional neural nets. Then, a number of candidates are selected from the unannotated samples for classifier updating, in which we apply the current classifiers ranking the samples by the prediction confidence. In particular, our approach utilizes the high-confidence and low-confidence samples in the self-paced and the active user-query way, respectively. The neural nets are later fine-tuned based on the updated classifiers. Such heuristic implementation is formulated as solving a concise active SPL optimization problem, which also advances the SPL development by supplementing a rational dynamic curriculum constraint. The new model finely accords with the "instructor-student-collaborative" learning mode in human education. The advantages of this proposed framework are two-folds: i) The required number of annotated samples is significantly decreased while the comparable performance is guaranteed. A dramatic reduction of user effort is also achieved over other state-of-the-art active learning techniques. ii) The mixture of SPL and AL effectively improves not only the classifier accuracy compared to existing AL/SPL methods but also the robustness against noisy data. We evaluate our framework on two challenging datasets, which include hundreds of persons under diverse conditions, and demonstrate very promising results. Please find the code of this project at: http://***/projects/aspl/ Copyright © 201

关键词： Cost effectiveness

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A Parallel Algorithm for Finding All Pairs κ-Mismatch Maximal Common Substrings

A Parallel Algorithm for Finding All Pairs κ-Mismatch Maxim...

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Supercomputing Conference

作者： Sriram P. Chockalingam Sharma V. Thankachan Srinivas Aluru Dept. of Computer Science and Engineering Indian Institute of Technology Mumbai India School of Computational Science and Engineering Georgia Institute of Technology Atlanta USA

ISBN: (纸本)9781467388160

We present an efficient parallel algorithm for the following problem: Given an input collection D of n sequences of total length N, a length threshold f and a mismatch threshold κ, report all κ-mismatch maximal common substrings of length at least f over all pairs of strings in D. This problem is motivated by clustering and assembly applications in computational biology, where D is a collection of millions of short DNA sequences. Sequencing errors and massive size of these datasets necessitate efficient parallel approximate sequence matching algorithms. We present a novel distributed memory parallel algorithm that solves this approximate sequence matching problem in O ((N/p log N + occ)log k N) expected time and takes only O(log k+1 N) expected rounds of global communications, under some realistic assumptions, where p is the number of processors and occ is the output size. To our knowledge, this is the first provably sub-quadratic time algorithm for solving this problem. We demonstrate the performance and scalability of our algorithm using large high throughput sequencing data sets.

关键词： Program processors Parallel algorithms Arrays Sequential analysis Electronic mail Clustering algorithms

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3D Model Reconstruction of Rocks on a Slope for Simulating a Rock Fall 1

3D Model Reconstruction of Rocks on a Slope for Simulating a...

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1st Geo-Chicago Conference: Sustainability and Resiliency in Geotechnical engineering, Geo-Chicago 2016

作者： Kitahra, Itaru Atsumi, Shogo Degawa, Ryo Kawamura, Yohiei Jang, Hyongdoo Ohta, Yuichi Dept. of Intelligent Interaction Technology Univ. of Tsukuba Tennoudai 1-1-1 TsukubaTsukuba Ibaraki305-8573 Japan Center for Computational Science Univ. of Tsukuba Tennoudai 1-1-1 Ibaraki305-8573 Japan Dept. of Mining Engineering and Metallurgical Engineering Curtin Univ. Locked Bag 30 KalgoorlieWA6433 Australia

ISBN: (数字)9780784480120

ISBN: (纸本)9780784480182

For reducing damage of rock fall, it is important to estimate the route, leap height and velocity of the rock. Although research about estimation of falling motion of rocks are actively conducted, there are still unsolved issues, since rock fall is a complex phenomenon affected by position, size, or shape of rocks and angle of slope. This paper proposes a method of rock fall simulation using a 3D model of rock and slope reconstructed by merging multiple-view images. The proposed method requires only a mobile camera to generate a 3D model, so that more practical rock fall simulation can be realized. In addition, reconstructing textured 3D model makes inspectors visually confirm how the rock falls on the slope. Due to the difficulty capturing multiple images of both of rocks and a slope at a same time, rocks and a slope are individually captured, and then, they are merged in the post process. There are two problems to be solved for merging them accurately. One is the significant difference in their spatial resolution;the other is the difference in the appearance caused by perspective projection. We conduct an experiments using multiple images of rocks and slopes captured at actual landslide site. © ASCE.

关键词： Rocks

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A multi-year search for transits of proxima centauri. i: Light curves corresponding to published ephemerides.

arXiv

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arXiv 2018年

作者： Blank, David L. Feliz, Dax Collins, Karen A. White, Graeme L. Stassun, Keivan G. Curtis, Ivan A. Hart, Rhodes Kielkopf, John F. Nelson, Peter Relles, Howard Stockdale, Christopher Jayawardene, Bandupriya Pennypacker, Carlton R. Shankland, Paul Reichart, Daniel E. Haislip, Joshua B. Kouprianov, Vladimir V. University of Southern Queensland Computational Engineering and Science Research Centre ToowoombaQLD4350 Australia Department of Physics Fisk University 1000 17th Avenue North NashvilleTN37208 United States Department of Physics and Astronomy Vanderbilt University NashvilleTN37235 United States Harvard-Smithsonian Center for Astrophysics CambridgeMA02138 United States ICO AdelaideSA Australia Department of Physics and Astronomy University of Louisville LouisvilleKY40292 United States Ellinbank Observatory VIC Australia Hazelwood Observatory ChurchillVIC Australia Physical Sciences Group College of Science and Engineering James Cook University TownsvilleQLD4811 Australia Lawrence Berkeley National Laboratory Dept. of Physics University of California Berkeley BerkeleyCA94720-7300 United States U.S. Naval Observatory Flagstaff Station 10391 W Naval Observatory Rd FlagstaffAZ86001 United States Department of Physics and Astronomy University of North Carolina at Chapel Hill Campus Box 3255 Chapel HillNC27599 United States

Proxima Centauri has become the subject of intense study since the radial-velocity discovery by Anglada-Escudé et al. (2016) of a planet orbiting this nearby M-dwarf every - 11.2 days. If Proxima Centauri b transits its host star, independent confirmation of its existence is possible, and its mass and radius can be measured in units of the stellar host mass and radius. To date, there have been three independent claims of possible transit-like event detections in light curve observations obtained by the MOST satellite (in 2014–15), the BSST telescope in Antarctica (in 2016), and the Las Campanas Observatory (in 2016). The claimed possible detections are tentative, due in part to the variability intrinsic to the host star, and in the case of the ground-based observations, also due to the limited duration of the light curve observations. Here, we present preliminary results from an extensive photometric monitoring campaign of Proxima Centauri, using telescopes around the globe and spanning from 2006 to 2017, comprising a total of 329 observations. Considering our data that coincide directly and/or phased with the previously published tentative transit detections, we are unable to independently verify those claims. We do, however, verify the previously reported ubiquitous and complex variability of the host star. We discuss possible interpretations of the data in light of the previous claims, and we discuss future analyses of these data that could more definitively verify or refute the presence of transits associated with the radial-velocity discovered planet. Copyright © 2018, The Authors. All rights reserved.

关键词： Telescopes

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The gravity collective: A search for the electromagnetic counterpart to the neutron star-black hole merger GW190814

arXiv

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arXiv 2021年

作者： Kilpatrick, Charles D. Coulter, David A. Arcavi, Iair Brink, Thomas G. Dimitriadis, Georgios Filippenko, Alexei V. Foley, Ryan J. Howell, D. Andrew Jones, David O. Makler, Martin Piro, Anthony L. Rojas-Bravo, César Sand, David J. Swift, Jonathan J. Tucker, Douglas Zheng, Weikang Allam, Sahar S. Annis, James T. Antilen, Juanita Bachmann, Tristan G. Bloom, Joshua S. Bom, Clecio R. Bostroem, K. Azalee Brout, Dillon Burke, Jamison Butler, Robert E. Butner, Melissa Campillay, Abdo Clever, Karoli E. Conselice, Christopher J. Cooke, Jeff Dage, Kristen C. de Carvalho, Reinaldo R. Jaeger, Thomas D.E. Desai, Shantanu Garcia, Alyssa Garcia-Bellido, Juan Gill, Mandeep S.S. Girish, Nachiket Hallakoun, Na'Ama Herner, Kenneth Hiramatsu, Daichi Holz, Daniel E. Huber, Grace Kawash, Adam M. McCully, Curtis Medallon, Sophia A. Metzger, Brian D. Modak, Shaunak Morgan, Robert Muñoz, Ricardo R. Muñoz-Elgueta, Nahir Murakami, Yukei S. Olivares, Felipe E. Palmese, Antonella Patra, Kishore Pereira, Maria E.S. Pessi, Thallis L. Pineda-Garcia, J. Quirola-Vásquez, Jonathan Ramirez-Ruiz, Enrico Rembold, Sandro Barboza Rest, Armin Rodríguez, Ósmar Santana-Silva, Luidhy Sherman, Nora F. Siebert, Matthew R. Smith, Carli Smith, J. Allyn Soares-Santos, Marcelle Stacey, Holland Stahl, Benjamin E. Strader, Jay Strasburger, Erika Sunseri, James Tinyanont, Samaporn Tucker, Brad E. Ulloa, Natalie Valenti, Stefano Vasylyev, Sergiy Wiesner, Matthew P. Zhang, Keto D. Northwestern University EvanstonIL60208 United States Department of Astronomy and Astrophysics University of California Santa CruzCA95064 United States The School of Physics and Astronomy Tel Aviv University Tel Aviv69978 Israel CIFAR Azrieli Global Scholars program CIFAR Toronto Canada Department of Astronomy University of California BerkeleyCA94720-3411 United States Miller Institute for Basic Research in Science University of California BerkeleyCA94720 United States Department of Physics University of California Santa BarbaraCA93106-9530 United States Las Cumbres Observatory 6740 Cortona Dr Suite 102 GoletaCA93117-5575 United States International Center for Advanced Studies & Instituto de Ciencias Físicas ECyT-UNSAM & CONICET Buenos Aires1650 Argentina Centro Brasileiro de Pesquisas Físicas Rua Dr. Xavier Sigaud 150 Rio de Janeiro RJCEP 22290-180 Brazil The Observatories of the Carnegie Institution for Science 813 Santa Barbara St. PasadenaCA91101 United States Steward Observatory University of Arizona 933 North Cherry Avenue TucsonAZ85721-0065 United States Thacher Observatory Thacher School 5025 Thacher Rd. OjaiCA93023 United States Fermi National Accelerator Laboratory P. O. Box 500 BataviaIL60510 United States Departamento de Astronomía Universidad de Chile Camino El Observatorio 1515 Las Condes Santiago Chile Department of Astronomy and Astrophysics University of Chicago ChicagoIL60637 United States Lawrence Berkeley National Laboratory 1 Cyclotron Road MS 50B-4206 BerkeleyCA94720-3411 United States Centro Federal de Educação Tecnológica Celso Suckow da Fonseca Rodovia Mário Covas lote J2 quadra J Itaguaí RJCEP 23810-000 Brazil Department of Physics and Astronomy University of California DavisCA95616 United States Center for Astrophysics Harvard & Smithsonian 60 Garden St CambridgeMA02138 United States Department of Astronomy Indiana University 727 E. Third St. BloomingtonIN47405 United States Dep

We present optical follow-up imaging obtained with the Katzman Automatic Imaging Telescope, Las Cumbres Observatory Global Telescope Network, Nickel Telescope, Swope Telescope, and Thacher Telescope of the LIGO/Virgo gravitational wave (GW) signal from the neutron star–black hole (NSBH) merger GW190814. We searched the GW190814 localization region (19 deg2 for the 90th percentile best localization), covering a total of 51 deg2 and 94.6% of the two-dimensional localization region. Analyzing the properties of 189 transients that we consider as candidate counterparts to the NSBH merger, including their localizations, discovery times from merger, optical spectra, likely host-galaxy redshifts, and photometric evolution, we conclude that none of these objects are likely to be associated with GW190814. Based on this finding, we consider the likely optical properties of an electromagnetic counterpart to GW190814, including possible kilonovae and short gamma-ray burst afterglows. Using the joint limits from our follow-up imaging, we conclude that a counterpart with an rband decline rate of 0.68 mag day−1, similar to the kilonova AT 2017gfo, could peak at an absolute magnitude of at most −17.8 mag (50% confidence). Our data are not constraining for "red" kilonovae and rule out "blue" kilonovae with M > 0.5 M* (30% confidence). We strongly rule out all known types of short gamma-ray burst afterglows with viewing angles ◦ assuming an initial jet opening angle of ∼ 5.2◦ and explosion energies and circumburst densities similar to afterglows explored in the literature. Finally, we explore the possibility that GW190814 merged in the disk of an active galactic nucleus, of which we find four in the localization region, but we do not find any candidate counterparts among these sources. © 2021, CC BY.

关键词： Stars

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Parallel discrete event simulation: The making of a field 17

Parallel discrete event simulation: The making of a field

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Simulation Winter Conference

作者： Richard M. Fujimoto Rajive Bagrodia Randal E. Bryant K. Mani Chandy David Jefferson Jayadev Misra David Nicol Brian Unger School of Computational Science and Engineering Georgia Institute of Technology Atlanta GA USA Scalable Network Technologies Inc. Culver City CA Computer Science Dept. University of California Los Angeles CA USA Computer Science Department Carnegie Mellon University Pittsburgh PA USA Computing and Mathematical Sciences Department California Institute of Technology Pasadena CA USA Lawrence Livermore National Laboratory Livermore CA USA Computer Science Department The University of Texas at Austin Austin TX USA Department of Electrical and Computer Engineering University of Illinois Urbana Champaign Urbana IL USA Computer Science Department University of Calgary Calgary Alberta Canada

ISBN: (纸本)9781538634271

Originating in the 1970's, the parallel discrete event simulation (PDES) field grew from a group of researchers focused on determining how to execute a discrete event simulation program on a parallel computer while still obtaining the same results as a sequential execution. Over the decades that followed the field expanded, grew, and flourishes to this day. This paper describes the origins and development of the field in the words of many who were deeply involved. Unlike other published work focusing on technical issues, the emphasis here is on historical aspects that are not recorded elsewhere, providing a unique characterization of how the field was created and developed.

关键词：

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Transfer Learning for Survival Analysis via Efficient L2,1-Norm Regularized Cox Regression

Transfer Learning for Survival Analysis via Efficient L2,1-N...

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IEEE International Conference on data Mining (ICDM)

作者： Yan Li Lu Wang Jie Wang Jieping Ye Chandan K. Reddy Dept. of Computational Medicine and Bioinformatics University of Michigan Ann Arbor MI Dept. of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI Dept. of Computer Science Wayne State University Detroit MI Dept. of Computer Science Virginia Tech Arlington VA

ISBN: (纸本)9781509054749

In survival analysis, the primary goal is to monitor several entities and model the occurrence of a particular event of interest. In such applications, it is quite often the case that the event of interest may not always be observed during the study period and this gives rise to the problem of censoring which cannot be easily handled in the standard regression approaches. In addition, obtaining sufficient labeled training instances for learning a robust prediction model is a very time consuming process and can be extremely difficult in practice. In this paper, we propose a transfer learning based Cox method, called Transfer-Cox, which uses auxiliary data to augment learning when there are insufficient amount of training examples. The proposed method aims to extract "useful" knowledge from the source domain and transfer it to the target domain, thus potentially improving the prediction performance in such time-to-event data. The proposed method uses the l 2,1 -norm penalty to encourage multiple predictors to share similar sparsity patterns, thus learns a shared representation across source and target domains, potentially improving the model performance on the target task. To speedup the computation, we apply the screening approach and extend the strong rule to sparse survival analysis models in multiple high-dimensional censored datasets. We demonstrate the performance of the proposed transfer learning method using several synthetic and high-dimensional microarray gene expression benchmark datasets and compare with other related competing state-of-the-art methods. Our results show that the proposed screening approach significantly improves the computational efficiency of the proposed algorithm without compromising the prediction performance. We also demonstrate the scalability of the proposed approach and show that the time taken to obtain the results is linear with respect to both the number of instances and features.

关键词： Analytical models Learning systems data models Hazards Predictive models Prediction algorithms Standards

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Realizing farthest-point voronoi diagrams 28

Realizing farthest-point voronoi diagrams

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28th Canadian Conference on computational Geometry, CCCG 2016

作者： Biedl, Therese Grimm, Carsten Palios, Leonidas Shewchuk, Jonathan Verdonschot, Sander Cheriton School of Computer Science University of Waterloo Canada Computational Geometry Lab School of Computer Science Carleton University OttawaON Canada Institut für Simulation und Graphik Fakultät für Informatik Otto-von-Guericke-Universität Magdeburg Magdeburg Germany Dept. of Computer Science and Engineering University of Ioannina Greece Computer Science Division University of California BerkeleyCA United States School of Electrical Engineering and Computer Science University of Ottawa OttawaON Canada

The farthest-point Voronoi diagram of a set of n sites is a tree with n leaves. We investigate whether arbitrary trees can be realized as farthest-point Voronoi diagrams. Given an abstract ordered tree T with n leaves and prescribed edge lengths, we produce a set of n sites S in O(n) time such that the farthest-point Voronoi diagram of S represents T. We generalize this algorithm to smooth, strictly convex, symmetric distance functions. Lastly, given a subdivision Z of Rk with k a small constant, we check in linear time whether Z realizes a kdimensional farthest-point Voronoi diagram. © Canadian Conference on computational Geometry, CCCG *** right reserved.

关键词： Graphic methods

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Overview of the CL-SciSumm 2016 Shared Task

Overview of the CL-SciSumm 2016 Shared Task

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Joint Workshop on Bibliometric-Enhanced Information Retrieval and Natural Language Processing for Digital Libraries, BIRNDL 2016

作者： Jaidka, Kokil Chandrasekaran, Muthu Kumar Rustagi, Sajal Kan, Min-Yen Big Data Experience Lab Adobe Research India India School of Computing National University of Singapore Singapore Singapore Dept. of Computer Science and Engineering Indian Institute of Technology Roorkee India Interactive and Digital Media Institute National University of Singapore Singapore Singapore

The CL-SciSumm 2016 Shared Task is the first medium-scale shared task on scientific document summarization in the computational linguistics (CL) domain. The task built off of the experience and training data set created in its namesake pilot task, which was conducted in 2014 by the same organizing committee. The track included three tasks involving: (1A) identifying relationships between citing documents and the referred document, (1B) classifying the discourse facets, and (2) generating the abstractive summary. The dataset comprised 30 annotated sets of citing and reference papers from the open access research papers in the CL domain. This overview paper describes the participation and the official results of the second CL-SciSumm Shared Task, organized as a part of the Joint Workshop onBibliometric-enhanced Information Retrieval and Natural Language Processing for Digital Libraries (BIRNDL 2016), held in New Jersey,USA in June, 2016. The annotated dataset used for this shared task and the scripts used for evaluation can be accessed and used by the community at: https://***/WING-NUS/scisumm-corpus.

关键词： Digital libraries

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Broadband multi-wavelength properties of M87 during the 2017 event Horizon telescope campaign

arXiv

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arXiv 2021年

作者： Algaba, J.C. Anczarski, J. Asada, K. Baloković, M. Chandra, S. Cui, Y.-Z. Falcone, A.D. Giroletti, M. Goddi, C. Hada, K. Haggard, Daryl Jorstad, S. Kaur, A. Kawashima, T. Keating, G. Kim, J.-Y. Kino, M. Komossa, S. Kravchenko, E.V. Krichbaum, T.P. Lee, S.-S. Lu, R.-S. Lucchini, M. Markoff, S. Neilsen, J. Nowak, M.A. Park, J. Principe, G. Ramakrishnan, V. Reynolds, M.T. Sasada, M. Savchenko, S.S. Williamson, K.E. Akiyama, Kazunori Alberdi, Antxon Alef, Walter Anantua, Richard Azulay, Rebecca Baczko, Anne-Kathrin Ball, David Barrett, John Bintley, Dan Benson, Bradford A. Blackburn, Lindy Blundell, Raymond Boland, Wilfred Bouman, Katherine L. Bower, Geoffrey C. Boyce, Hope Bremer, Michael Brinkerink, Christiaan D. Brissenden, Roger Britzen, Silke Broderick, Avery E. Broguiere, Dominique Byun, Do-Young Carlstrom, John E. Chael, Andrew Chan, Chi-Kwan Chatterjee, Shami Chatterjee, Koushik Chen, Ming-Tang Chen, Yongjun Chesler, Paul M. Cho, Ilje Christian, Pierre Conway, John E. Cordes, James M. Crawford, Thomas M. Crew, Geoffrey B. Cruz-Osorio, Alejandro Davelaar, Jordy de Laurentis, Mariafelicia Deane, Roger Dempsey, Jessica Desvignes, Gregory Dexter, Jason Doeleman, Sheperd S. Eatough, Ralph P. Falcke, Heino Farah, Joseph Fish, Vincent L. Fomalont, Ed Ford, H. Alyson Fraga-Encinas, Raquel Friberg, Per Fromm, Christian M. Fuentes, Antonio Galison, Peter Gammie, Charles F. García, Roberto Gentaz, Olivier Georgiev, Boris Gold, Roman Gómez, José L. Gómez-Ruiz, Arturo I. Gu, Minfeng Gurwell, Mark Hecht, Michael H. Hesper, Ronald Ho, Luis C. Ho, Paul Honma, Mareki Huang, Chih-Wei L. Huang, Lei Hughes, David H. Ikeda, Shiro Inoue, Makoto Issaoun, Sara James, David J. Jannuzi, Buell T. Janssen, Michael Jeter, Britton Jiang, Wu Jiménez-Rosales, Alejandra Johnson, Michael D. Jung, Taehyun Karami, Mansour Karuppusamy, Ramesh Kettenis, Mark Bellaterra BarcelonaE-08193 Spain Dipartimento di Fisica Università di Trieste TriesteI-34127 Italy INAF Trieste Dept. of Physics and Astronomy University of Bologna Italy Department of Physics Faculty of Science University of Malaya Kuala Lumpur50603 Malaysia Department of Physics Villanova University 800 E. Lancaster Avenue VillanovaPA19085 United States Institute of Astronomy and Astrophysics Academia Sinica 11F of Astronomy-Mathematics Building AS/NTU No. 1 Sec. 4 Roosevelt Rd Taipei10617 Taiwan Yale Center for Astronomy & Astrophysics 52 Hillhouse Avenue New HavenCT06511 United States Department of Physics Yale University P.O. Box 2018120 New HavenCT06520 United States Centre for Space Research North-West University Potchefstroom2520 South Africa 2-21-1 Osawa Mitaka Tokyo181-8588 Japan Mizusawa VLBI Observatory 2-12 Hoshigaoka Mizusawa Oshu Iwate023-0861 Japan 525 Davey Laboratory Department of Astronomy and Astrophysics Pennsylvania State University University ParkPA16802 United States INAF Istituto di Radioastronomia Via P. Gobetti 101 BolognaI-40129 Italy Radboud University P.O. Box 9010 Nijmegen6500 GL Netherlands Leiden Observatory-Allegro Leiden University P.O. Box 9513 Leiden2300 RA Netherlands Department of Physics McGill University 3600 University Street MontréalQCH3A 2T8 Canada McGill Space Institute McGill University 3550 University Street MontréalQCH3A 2A7 Canada Institute for Astrophysical Research Boston University 725 Commonwealth Avenue BostonMA02215 United States Astronomical Institute St. Petersburg University Universitetskij Pr. 28 Petrodvorets St. Petersburg198504 Russia Institute for Cosmic Ray Research The University of Tokyo 5-1-5 Kashiwanoha Kashiwa Chiba277-8582 Japan Center for Astrophysics Harvard & Smithsonian 60 Garden Street CambridgeMA02138 United States Korea Astronomy and Space Science Institute Daedeok-daero 776 Yuseong-gu Daejeon34055 Korea Republic of M

In 2017, the Event Horizon Telescope (EHT) Collaboration succeeded in capturing the first direct image of the center of the M87 galaxy. The asymmetric ring morphology and size are consistent with theoretical expectations for a weakly accreting supermassive black hole of mass ∼6.5 × 109M☉. The EHTC also partnered with several international facilities in space and on the ground, to arrange an extensive, quasi-simultaneous multi-wavelength campaign. This Letter presents the results and analysis of this campaign, as well as the multi-wavelength data as a legacy data repository. We captured M87 in a historically low state, and the core flux dominates over HST-1 at high energies, making it possible to combine core flux constraints with the more spatially precise very long baseline interferometry data. We present the most complete simultaneous multi-wavelength spectrum of the active nucleus to date, and discuss the complexity and caveats of combining data from different spatial scales into one broadband spectrum. We apply two heuristic, isotropic leptonic single-zone models to provide insight into the basic source properties, but conclude that a structured jet is necessary to explain M87's spectrum. We can exclude that the simultaneous γ-ray emission is produced via inverse Compton emission in the same region producing the EHT mm-band emission, and further conclude that the γ-rays can only be produced in the inner jets (inward of HST-1) if there are strongly particle-dominated regions. Direct synchrotron emission from accelerated protons and secondaries cannot yet be excluded. © 2021, CC BY.

关键词： Gravitation

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