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Determination of Disk Thickness of Face-on Spiral Galaxies and Image Processing Method^1,2

Chinese Astronomy and Astrophysics 2015年第2期39卷 166-176页

作者： Hu, Tao Peng, Q.-H. Department of Automation Shanghai University Shanghai 200072 China Key Laboratory for the Structure and Evolution of Celestial Bodies Chinese Academy of Sciences Kunming 650011 China School of Astronomy and Space Science Nanjing University Nanjing 210093 China

It is unable to obtain the disk thickness of a face-on spiral galaxy by measuring its surface brightness distribution. Here, in order to obtain the disk thickness of faced-on spiral galaxies, we determine the scale heights of their disks using an analytical method, based on the asymptotic solution of Poison's equation of gravitational potential in a 3-D galactic disk under the equiangular logarithmic spiral type of density perturbation. For measuring the key parameter, namely the innermost position of spiral arms (forbidden radius r0), and free from the effect of light contamination of galactic bulge, an improved image processing method is used in this study by subtracting a two-component (disk+bulge) brightness model from the observed galaxy image. On the basis of some fitted and measured fundamental parameters of spiral structures, we obtain the disk thickness and other parameters for the two face-on spiral galaxies: one normal spiral galaxy (S) and one spiral bar galaxy (SB), and their ratio parameters (the scale ratio of bulge and disk rb/rd, and the ratio of disk scale and thickness rd/H) are also derived. By using this improved method of two-component subtraction, it is easy to obtain the forbidden radius r0, which is smaller than that obtained by measuring directly the original galaxy image, thus the obtained effective thickness of galactic disks becomes thinner. © 2015.

关键词： Galaxies: disk Galaxies: fundamental parameters Galaxies: spiral Galaxies: structure

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Gravitational Test beyond the First Post-Newtonian Order with the Shadow of the M87 Black Hole

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Physical Review Letters 2020年第14期125卷 141104-141104页

作者： Dimitrios Psaltis Lia Medeiros Pierre Christian Feryal Özel Kazunori Akiyama Antxon Alberdi Walter Alef Keiichi Asada Rebecca Azulay David Ball Mislav Baloković John Barrett Dan Bintley Lindy Blackburn Wilfred Boland Geoffrey C. Bower Michael Bremer Christiaan D. Brinkerink Roger Brissenden Silke Britzen Dominique Broguiere Thomas Bronzwaer Do-Young Byun John E. Carlstrom Andrew Chael Chi-kwan Chan Shami Chatterjee Koushik Chatterjee Ming-Tang Chen Yongjun Chen Ilje Cho John E. Conway James M. Cordes Geoffrey B. Crew Yuzhu Cui Jordy Davelaar Mariafelicia De Laurentis Roger Deane Jessica Dempsey Gregory Desvignes Jason Dexter Ralph P. Eatough Heino Falcke Vincent L. Fish Ed Fomalont Raquel Fraga-Encinas Per Friberg Christian M. Fromm Charles F. Gammie Roberto García Olivier Gentaz Ciriaco Goddi José L. Gómez Minfeng Gu Mark Gurwell Kazuhiro Hada Ronald Hesper Luis C. Ho Paul Ho Mareki Honma Chih-Wei L. Huang Lei Huang David H. Hughes Makoto Inoue Sara Issaoun David J. James Buell T. Jannuzi Michael Janssen Wu Jiang Alejandra Jimenez-Rosales Michael D. Johnson Svetlana Jorstad Taehyun Jung Mansour Karami Ramesh Karuppusamy Tomohisa Kawashima Garrett K. Keating Mark Kettenis Jae-Young Kim Junhan Kim Jongsoo Kim Motoki Kino Jun Yi Koay Patrick M. Koch Shoko Koyama Michael Kramer Carsten Kramer Thomas P. Krichbaum Cheng-Yu Kuo Tod R. Lauer Sang-Sung Lee Yan-Rong Li Zhiyuan Li Michael Lindqvist Rocco Lico Jun Liu Kuo Liu Elisabetta Liuzzo Wen-Ping Lo Andrei P. Lobanov Colin Lonsdale Ru-Sen Lu Jirong Mao Sera Markoff Daniel P. Marrone Alan P. Marscher Iván Martí-Vidal Satoki Matsushita Yosuke Mizuno Izumi Mizuno James M. Moran Kotaro Moriyama Monika Moscibrodzka Cornelia Müller Gibwa Musoke Alejandro Mus Mejías Hiroshi Nagai Neil M. Nagar Ramesh Narayan Gopal Narayanan Iniyan Natarajan Roberto Neri Aristeidis Noutsos Hiroki Okino Héctor Olivares Tomoaki Oyama Daniel C. M. Palumbo Jongho Park Nimesh Patel Ue-Li Pen Vincent Piétu Richard Plambeck Aleksandar PopStefanija Ben Prather Jorge A. Preciado-López Venkatessh Ramak Steward Observatory and Department of Astronomy University of Arizona 933 North Cherry Avenue Tucson Arizona 85721 USA School of Natural Sciences Institute for Advanced Study 1 Einstein Drive Princeton New Jersey 08540 USA National Radio Astronomy Observatory 520 Edgemont Road Charlottesville Virginia 22903 USA Massachusetts Institute of Technology Haystack Observatory 99 Millstone Road Westford Massachusetts 01886 USA National Astronomical Observatory of Japan 2-21-1 Osawa Mitaka Tokyo 181-8588 Japan Black Hole Initiative at Harvard University 20 Garden Street Cambridge Massachusetts 02138 USA Instituto de Astrofísica de Andalucía-CSIC Glorieta de la Astronomía s/n E-18008 Granada Spain Max-Planck-Institut für Radioastronomie Auf dem Hügel 69 D-53121 Bonn Germany Institute of Astronomy and Astrophysics Academia Sinica 11F of Astronomy-Mathematics Building AS/NTU No. 1 Sec. IV Roosevelt Road Taipei 10617 Taiwan Republic of China Departament d’Astronomia i Astrofísica Universitat de València C. Dr. Moliner 50 E-46100 Burjassot València Spain Observatori Astronmic Universitat de València C. Catedrático José Beltrán 2 E-46980 Paterna València Spain Center for Astrophysics–Harvard & Smithsonian 60 Garden Street Cambridge Massachusetts 02138 USA East Asian Observatory 660 North A’ohoku Place Hilo Hawaii 96720 USA Nederlandse Onderzoekschool voor Astronomie (NOVA) P.O. Box 9513 2300 RA Leiden Netherlands Institute of Astronomy and Astrophysics Academia Sinica 645 North A’ohoku Place Hilo Hawaii 96720 USA Institut de Radioastronomie Millimétrique 300 rue de la Piscine F-38406 Saint Martin d’Hères France Department of Astrophysics Institute for Mathematics Astrophysics and Particle Physics (IMAPP) Radboud University P.O. Box 9010 6500 GL Nijmegen Netherlands Korea Astronomy and Space Science Institute Daedeok-daero 776 Yuseong-gu Daejeon 34055 Republic of Korea University of Science and Technology Gajeong-ro 217 Yuseong-gu Daejeon 34113 Re

The 2017 Event Horizon Telescope (EHT) observations of the central source in M87 have led to the first measurement of the size of a black-hole shadow. This observation offers a new and clean gravitational test of the black-hole metric in the strong-field regime. We show analytically that spacetimes that deviate from the Kerr metric but satisfy weak-field tests can lead to large deviations in the predicted black-hole shadows that are inconsistent with even the current EHT measurements. We use numerical calculations of regular, parametric, non-Kerr metrics to identify the common characteristic among these different parametrizations that control the predicted shadow size. We show that the shadow-size measurements place significant constraints on deviation parameters that control the second post-Newtonian and higher orders of each metric and are, therefore, inaccessible to weak-field tests. The new constraints are complementary to those imposed by observations of gravitational waves from stellar-mass sources.

关键词： Astrophysical studies of gravity Classical black holes Experimental studies of gravity Astronomical black holes

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Constraints on black-hole charges with the 2017 EHT observations of M87*

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Physical Review D 2021年第10期103卷 104047-104047页

作者： Prashant Kocherlakota Luciano Rezzolla Heino Falcke Christian M. Fromm Michael Kramer Yosuke Mizuno Antonios Nathanail Héctor Olivares Ziri Younsi Kazunori Akiyama Antxon Alberdi Walter Alef Juan Carlos Algaba Richard Anantua Keiichi Asada Rebecca Azulay Anne-Kathrin Baczko David Ball Mislav Baloković John Barrett Bradford A. Benson Dan Bintley Lindy Blackburn Raymond Blundell Wilfred Boland Katherine L. Bouman Geoffrey C. Bower Hope Boyce Michael Bremer Christiaan D. Brinkerink Roger Brissenden Silke Britzen Avery E. Broderick Dominique Broguiere Thomas Bronzwaer Do-Young Byun John E. Carlstrom Andrew Chael Chi-kwan Chan Shami Chatterjee Koushik Chatterjee Ming-Tang Chen Yongjun Chen (陈永军) Paul M. Chesler Ilje Cho Pierre Christian John E. Conway James M. Cordes Thomas M. Crawford Geoffrey B. Crew Alejandro Cruz-Osorio Yuzhu Cui Jordy Davelaar Mariafelicia De Laurentis Roger Deane Jessica Dempsey Gregory Desvignes Sheperd S. Doeleman Ralph P. Eatough Joseph Farah Vincent L. Fish Ed Fomalont Raquel Fraga-Encinas Per Friberg H. Alyson Ford Antonio Fuentes Peter Galison Charles F. Gammie Roberto García Olivier Gentaz Boris Georgiev Ciriaco Goddi Roman Gold José L. Gómez Arturo I. Gómez-Ruiz Minfeng Gu (顾敏峰) Mark Gurwell Kazuhiro Hada Daryl Haggard Michael H. Hecht Ronald Hesper Luis C. Ho (何子山) Paul Ho Mareki Honma Chih-Wei L. Huang Lei Huang (黄磊) David H. Hughes Shiro Ikeda Makoto Inoue Sara Issaoun David J. James Buell T. Jannuzi Michael Janssen Britton Jeter Wu Jiang (江悟) Alejandra Jimenez-Rosales Michael D. Johnson Svetlana Jorstad Taehyun Jung Mansour Karami Ramesh Karuppusamy Tomohisa Kawashima Garrett K. Keating Mark Kettenis Dong-Jin Kim Jae-Young Kim Jongsoo Kim Junhan Kim Motoki Kino Jun Yi Koay Yutaro Kofuji Patrick M. Koch Shoko Koyama Carsten Kramer Thomas P. Krichbaum Cheng-Yu Kuo Tod R. Lauer Sang-Sung Lee Aviad Levis Yan-Rong Li (李彦荣) Zhiyuan Li (李志远) Michael Lindqvist Rocco Lico Greg Lindahl Jun Liu (刘俊) Kuo Liu Elisabetta Liuzzo Wen-Ping Lo Andrei P. Lobanov Laurent Loinard Colin Lonsdale Ru-Sen Lu Institut für Theoretische Physik Goethe-Universität Max-von-Laue-Strasse 1 60438 Frankfurt Germany Frankfurt Institute for Advanced Studies Ruth-Moufang-Strasse 1 60438 Frankfurt Germany School of Mathematics Trinity College Dublin 2 Ireland Department of Astrophysics Institute for Mathematics Astrophysics and Particle Physics (IMAPP) Radboud University P.O. Box 9010 6500 GL Nijmegen Netherlands Black Hole Initiative at Harvard University 20 Garden Street Cambridge Massachusetts 02138 USA Center for Astrophysics—Harvard & Smithsonian 60 Garden Street Cambridge Massachusetts 02138 USA Max-Planck-Institut für Radioastronomie Auf dem Hügel 69 D-53121 Bonn Germany Tsung-Dao Lee Institute and School of Physics and Astronomy Shanghai Jiao Tong University Shanghai 200240 China Institut für Theoretische Physik Goethe-Universität Frankfurt Max-von-Laue-Straße 1 D-60438 Frankfurt am Main Germany Department of Physics National and Kapodistrian University of Athens Panepistimiopolis GR 15783 Zografos Greece Mullard Space Science Laboratory University College London Holmbury St. Mary Dorking Surrey RH5 6NT United Kingdom Massachusetts Institute of Technology Haystack Observatory 99 Millstone Road Westford Massachusetts 01886 USA National Astronomical Observatory of Japan 2-21-1 Osawa Mitaka Tokyo 181-8588 Japan Instituto de Astrofísica de Andalucía-CSIC Glorieta de la Astronomía s/n E-18008 Granada Spain Department of Physics Faculty of Science University of Malaya 50603 Kuala Lumpur Malaysia Center for Computational Astrophysics Flatiron Institute 162 Fifth Avenue New York New York 10010 USA Institute of Astronomy and Astrophysics Academia Sinica 11F of Astronomy-Mathematics Building AS/NTU No. 1 Sec. 4 Roosevelt Rd Taipei 10617 Taiwan R.O.C. Departament d’Astronomia i Astrofísica Universitat de València C. Dr. Moliner 50 E-46100 Burjassot València Spain Observatori Astronòmic Universitat de València C. Catedrático José Beltrán 2 E-46980 Paterna

Our understanding of strong gravity near supermassive compact objects has recently improved thanks to the measurements made by the Event Horizon Telescope (EHT). We use here the M87* shadow size to infer constraints on the physical charges of a large variety of nonrotating or rotating black holes. For example, we show that the quality of the measurements is already sufficient to rule out that M87* is a highly charged dilaton black hole. Similarly, when considering black holes with two physical and independent charges, we are able to exclude considerable regions of the space of parameters for the doubly-charged dilaton and the Sen black holes.

关键词： Alternative gravity theories Experimental studies of gravity General relativity Radio, microwave, & sub-mm astronomy Accretion disk & black-hole plasma Classical black holes Galaxies Electromagnetic radiation astronomy

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Prompt optical emission from gamma-ray bursts with multiple timescale variability of central engine activities

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Research in Astronomy and Astrophysics 2014年第4期14卷 411-422页

作者： Si-Yao Xu Zhuo Li Department of Astronomy and Kavli Institute for Astronomy and Astrophysics Peking University Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences

Complete high-resolution light curves of GRB 080319B observed by Swift present an opportunity for detailed temporal analysis of prompt optical emission. With a two-component distribution of initial Lorentz factors, we simulate the dynamical process of shells being ejected from the central engine in the framework of the in- ternal shock model. The emitted radiations are decomposed into different frequency ranges for a temporal correlation analysis between the light curves in different energy bands. The resulting prompt optical and gamma-ray emissions show similar tempo- ral profiles, with both showing a superposition of a component with slow variability and a component with fast variability, except that the gamma-ray light curve is much more variable than its optical counterpart. The variability in the simulated light curves and the strong correlation with a time lag between the optical and gamma-ray emis- sions are in good agreement with observations of GRB 080319B. Our simulations suggest that the variations seen in the light curves stem from the temporal structure of the shells injected from the central engine of gamma-ray bursts. Future observations with high temporal resolution of prompt optical emission from GRBs, e.g., by UFFO- Pathfinder and SVOM-GWAC, will provide a useful tool for investigating the central engine activity.

关键词： gamma rays： bursts- GRB 080319B

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On properties of mass transfer in an Algol-type binary system:an example of VV Vir

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Research in Astronomy and Astrophysics 2014年第2期14卷 179-192页

作者： Jia Zhang Sheng-Bang Qian Lin-Qiao Jiang Yunnan Observatories Chinese Academy of Sciences Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences University of Chinese Academy of Sciences

Some properties of mass transfer within a semi-detached binary system are discussed based on an example of VV Vir. The observations and analysis of VV Vir show that it is a semi-detached binary system with the less massive cooler component filling its Roche lobe, which is also called an Algol-type binary system. Based on the parameters of this semi-detached binary, a theoretical study on the mass flow is carded out, including the trajectory of the mass flow, the position, radius and temperature of the impact spot caused by the mass flow, the inconsistent form of the mass flow and the possibly huge rate of energy transfer carried by the mass flow. Humps and distortions in light curves of VV Vir are deemed to be weak evidence for the theoretical results.

关键词： binaries eclipsing -- stars individual （VV Vir） -- techniques photo-metric

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Observations of SN 2017ein reveal shock breakout emission and a massive progenitor star for a type Ic supernova

arXiv

引用

arXiv 2018年

作者： Xiang, Danfeng Wang, Xiaofeng Mo, Jun Wang, Lingjun Smartt, Stephen Fraser, Morgan Ehgamberdiev, Shuhrat A. Mirzaqulov, Davron Zhang, Jujia Zhang, Tianmeng Vinko, Jozsef Wheeler, J. Craig Hosseinzadeh, Griffin Howell, D. Andrew McCully, Curtis DerKacy, James M. Baron, E. Brown, Peter Zhang, Xianfei Bi, Shaolan Song, Hao Zhang, Kaicheng Rest, A. Nomoto, Kenichi Tolstov, Alexey Blinnikov, Sergei Tsinghua University Beijing100084 China Astroparticle Physics Institute of High Energy Physics Chinese Academy of Sciences Beijing100049 China Astrophysics Research Centre School of Mathematics and Physics Queens University Belfast BelfastBT7 1NN United Kingdom School of Physics University College Dublin Belfield Dublin 4 Ireland Ulugh Beg Astronomical Institute Uzbekistan Academy of Sciences Uzbekistan Tashkent100052 Uzbekistan Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China National Astronomical Observatory of China Chinese Academy of Sciences Beijing100012 China Konkoly Observatory MTA CSFK Konkoly Thege M. ut 15-17 Budapest1121 Hungary Department of Optics & Quantum Electronics University of Szeged Dom ter 9 Szeged6720 Hungary Department of Astronomy University of Texas at Austin AustinTX78712 United States Las Cumbres Observatory 6740 Cortona Drive Suite 102 GoletaCA93117-5575 United States Department of Physics University of California Santa BarbaraCA93106-9530 United States Homer L. Dodge Department of Physics and Astronomy University of Oklahoma NormanOK United States George P. and CynthiaWoods Mitchell Institute for Fundamental Physics & Astronomy Texas A. & M. University Department of Physics and Astronomy 4242 TAMU College StationTX77843 United States Department of Astronomy Beijing Normal University Beijing100875 China Space Telescope Science Institute 3700 San Martin Drive BaltimoreMD21218 United States Department of Physics and Astronomy Johns Hopkins University BaltimoreMD21218 United States University of Tokyo Institutes for Advanced Study University of Tokyo 5-1-5 Kashiwanoha Kashiwa Chiba277-8583 Japan Moscow117218 Russia Moscow127055 Rus

We present optical and ultraviolet observations of nearby type Ic supernova SN 2017ein as well as detailed analysis of its progenitor properties from both the early-time observations and the prediscovery Hubble Space Telescope (HST) images. The optical light curves started from within one day to ∼275 days after explosion, and optical spectra range from ∼2 days to ∼90 days after explosion. Compared to other normal SNe Ic like SN 2007gr and SN 2013ge, SN 2017ein seems to have more prominent CII absorption and higher expansion velocities in early phases, suggestive of relatively lower ejecta mass. The earliest photometry obtained for SN 2017ein show indications of shock cooling. The best-fit obtained by including a shock cooling component gives an estimate of the envelope mass as ∼0.02 M☉ and stellar radius as 8±4 R☉. Examining the pre-explosion images taken with the HST WFPC2, we find that the SN position coincides with a luminous and blue point-like source, with an extinction-corrected absolute magnitude of MV ∼−8.2 mag and MI∼−7.7 mag. Comparisons of the observations to the theoretical models indicate that the counterpart source was either a single WR star or a binary with whose members had high initial masses, or a young compact star cluster. To further distinguish between different scenarios requires revisiting the site of the progenitor with HST after the SN fades away. Copyright © 2018, The Authors. All rights reserved.

关键词： Supernovae

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Photometric investigation of the K-type extremely shallow contact binary V1799 Orion

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Research in Astronomy and Astrophysics 2014年第9期14卷 1157-1165页

作者： Nian-Ping Liu Sheng-Bang Qian Wen-Ping Liao Jia-Jia He Er-Gang Zhao Liang Liu Yunnan Observatories Chinese Academy of Sciences Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences University of Chinese Academy of Sciences

New multi-color light curves of the very short period K-type eclipsing binary V1799 Ori were obtained and analyzed with the Wilson-Devinney code. The photometric solutions reveal that the system is a W-type shallow-contact binary with a mass ratio of q = 1.335（4-0.005） and a degree of contact of about f = 3.5（-4-1.1）%. In general, the results are in good agreement with what is reported by Samec. Dramatic manifestations of the O＇Connell effect that appear in the light curves can be explained well by employing starspots on the binary surface, which confirms that the system is active at present. Several new times of light minimum were obtained. All the avail- able times of light minimum were collected, along with the recalculated and newly obtained values. Applying a least-squares method to the constructed O - C diagram, a new ephemeris is derived for V1799 Ori. The orbital period is found to show a continuous weak increase at a rate of 1.8（±0.6） × 10^-8 d yr^-1. The extremely shallow contact, together with the period increase, suggests that the binary may be at a critical stage predicted by thermal relaxation oscillation theory.

关键词： binaries： close -- binaries： eclipsing -- stars： individual （V1799 Off）

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The influences of convective overshooting and semiconvection on the chemical evolution of massive stars

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Research in Astronomy and Astrophysics 2014年第8期14卷 979-991页

作者： Cai-Yun Ding Yan Li Yunnan Observatories Chinese Academy of Sciences Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences University of Chinese Academy of Sciences

In massive stars, convection in the interior is different from that of inter- mediate and small mass stars. In the main-sequence phase of small mass stars, there is a convective core and a radiative envelope, between which are the radiative inter- mediate layers with uneven chemical abundances. Semiconvection would occur in the intermediate layers between the convective core and the homogeneous envelope in massive stars. We treat core convective overshooting and semiconvection together as a process. We found that when decreasing overshooting, the semiconvection is more pronounced. In these two processes, we introduce one diffusive parameter D, which is different from other authors who have introduced different parameters for these two zones. The influences of the turbulent diffusion process on chemical evolution and other quantities of the stellar structure are shown in the present paper.

关键词： stars evolution -- stars abundances -- convection -- diffusion

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New estimates of scale heights and spiral structures for non-edge-on spiral galaxies

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Research in Astronomy and Astrophysics 2014年第7期14卷 869-874页

作者： Tao Hu Qiu-He Peng Department of Automation Shanghai University Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesYunnan Observatories Department of Astronomy Nanjing University

On the basis of Poisson＇s equation for the logarithmic perturbation of matter density, we provide improved estimates of scale heights and spiral structures for non-edge-on spiral galaxies by subtracting the surface brightness distributions from observed images. As examples, the non-edge-on spiral galaxies PGC 24996, which is face-on, and M31, which is inclined, are studied. The scale height, pitch angle and inclination angle of M31, our nearest neighbor, that are presented in this work, agree well with previous research.

关键词： galaxy： disk -- galaxies： fundamental parameters -- galaxies： spiral --galaxies： structure

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MILLISECOND PULSAR ORIGIN OF THE GALACTIC CENTER EXCESS AND EXTENDED GAMMA-RAY EMISSION FROM ANDROMEDA – A CLOSER LOOK

arXiv

引用

arXiv 2017年

作者： Eckner, Christopher Hou, Xian Serpico, Pasquale D. Winter, Miles Zaharijas, Gabrijela Martin, Pierrick di Mauro, Mattia Mirabal, Nestor Petrovic, Jovana Prodanovic, Tijana Vandenbroucke, Justin Laboratory for Astroparticle Physics University of Nova Gorica Vipavska 13 Nova GoricaSI-5000 Slovenia Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunmin650216 P China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China LAPTh Université Savoie Mont Blanc & CNRS Annecy Cedex74941 France Universit of Wisconsin Madison 500 Lincoln Drive MadisonWI53706 United States Istituto Nazionale di Fisica Nucleare - Sezione Trieste Padriciano 99 TriesteI-34149 Italy Institut de Recherche en Astrophysique et Planétologie CNRS-INSU Université Paul Sabatier 9 avenue Colonel Roche Toulouse Cedex 4BP 4434631028 France 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 CRESST/CSST Department of Physics UMBC BaltimoreMD21250 United States NASA Goddard Space Flight Center GreenbeltMD20771 United States Department of Physics Faculty of Sciences University of Novi Sad Trg Dositeja Obradovića 4 Novi Sad21000 Serbia

A new measurement of a spatially extended gamma-ray signal from the center of the Andromeda galaxy (M31) has been recently published by the Fermi-LAT collaboration, reporting that the emission broadly resembles the so-called Galactic center excess (GCE) of the Milky Way (MW). Steadily, the weight of the evidence is accumulating on a millisecond pulsar (MSPs) origin for the GCE. These elements prompt us to compare the mentioned observations with what is, perhaps, the simplest model for an MSP population, solely obtained by rescaling of the MSP luminosity function determined in the local MW disk via the respective stellar mass of the systems. Remarkably, we find that without free fitting parameters, this model can account for both the energetics and the morphology of the GCE within uncertainties. For M31, the estimated luminosity due to primordial MSPs is expected to contribute only about a quarter of the detected emission, although a stronger contribution cannot be excluded given the large uncertainties. If correct, the model predicts that the M31 disk emission due to MSPs is not far below the present upper bound. We also discuss additional refinements of this simple model. Using the correlation between globular cluster gamma-ray luminosity and stellar encounter rate, we gauge the dynamical MSP formation in the bulge. This component is expected to contribute to the GCE only at a level . 5%, but it could affect the signal’s morphology. We also comment on limitations of our model as well as on future perspectives for improved diagnostics. Subject headings: galaxies: Milky Way and dwarf spheroidal — gamma-rays: millisecond pulsars — X-rays: binaries Copyright © 2017, The Authors. All rights reserved.

关键词： Galaxies

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