Acciari, V. A., Ansoldi, S., Antonelli, L. A., Arbet Engels, A., Baack, D., Babić, A., Banerjee, B., Barres de Almeida, U., Barrio, J. A., Becerra González, J., Bednarek, W., Bellizzi, L., Bernardini, E., Berti, A., Besenrieder, J., Bhattacharyya, W., Bigongiari, C., Biland, A., … Zarić, D. (2020). MAGIC observations of the diffuse γ-ray emission in the vicinity of the Galactic center. Astronomy & Astrophysics, 642, A190. https://doi.org/10.1051/0004-6361/201936896
MAGIC observations of the diffuse γ-ray emission in the vicinity of the Galactic center
|Author:||Acciari, V. A.1,2; Ansoldi, S.3,4,5,6,7,8; Antonelli, L. A.9;|
1Inst Astrofis Canarias, San Cristobal la Laguna 38200, Spain.
2Univ La Laguna, Dept Astrofis, San Cristobal la Laguna 38206, Tenerife, Spain.
3Univ Udine, I-33100 Udine, Italy.
4INFN Trieste, I-33100 Udine, Italy.
5Univ Tokyo, ICRR, Japanese MAGIC Consortium, Chiba 2778582, Japan.
6Kyoto Univ, Dept Phys, Kyoto 6068502, Japan.
7Tokai Univ, Hiratsuka, Kanagawa 2591292, Japan.
8RIKEN, Saitama 3510198, Japan.
9Natl Inst Astrophys INAF, I-00136 Rome, Italy.
10Swiss Fed Inst Technol, CH-8093 Zurich, Switzerland.
11Tech Univ Dortmund, D-44221 Dortmund, Germany.
12Univ Rijeka, Dept Phys, Croatian Consortium, Rijeka 51000, Croatia.
13Univ Split, FESB, Split 21000, Croatia.
14Univ Zagreb, FER, Zagreb 10000, Croatia.
15Univ Osijek, Osijek 31000, Croatia.
16Rudjer Boskovic Inst, Zagreb 10000, Croatia.
17HBNI, Saha Inst Nucl Phys, 1-AF Bidhannagar,Sect 1, Kolkata 700064, India.
18URCA, Ctr Brasileiro Pesquisas Fis CBPF, BR-22290180 Rio De Janeiro, RJ, Brazil.
19Univ Complutense Madrid, IPARCOS Inst, Madrid 28040, Spain.
20Univ Complutense Madrid, EMFTEL Dept, Madrid 28040, Spain.
21Univ Lodz, Dept Astrophys, PL-90236 Lodz, Poland.
22Univ Siena, I-53100 Siena, Italy.
23INFN Pisa, I-53100 Siena, Italy.
24DESY, D-15738 Zeuthen, Germany.
25Univ Padua, I-35131 Padua, Italy.
26Ist Nazl Fis Nucl, I-35131 Padua, Italy.
27Ist Nazl Fis Nucl, I-00044 Rome, Italy.
28Max Planck Inst Phys & Astrophys, D-80805 Munich, Germany.
29Barcelona Inst Sci & Technol BIST, Inst Fis Altes Energies IFAE, Barcelona 08193, Spain.
30Univ Pisa, I-56126 Pisa, Italy.
31INFN Pisa, I-56126 Pisa, Italy.
32NAS RA, ICRANet Armenia, Yerevan 0019, Armenia.
33Ctr Invest Energet Medioambientales & Tecnol, Madrid 28040, Spain.
34Port Informacio Cient PIC, Barcelona 08193, Spain.
35Univ Wurzburg, D-97074 Wurzburg, Germany.
36Univ Turku, Finnish Ctr Astron ESO FINCA, Finnish MAGIC Consortium, Turku 20014, Finland.
37Univ Oulu, Astron Res Unit, Oulu 90014, Finland.
38Univ Autonoma Barcelona, Dept Fis, Bellaterra 08193, Spain.
39Univ Autonoma Barcelona, CERES IEEC, Bellaterra 08193, Spain.
40Univ Trieste, Dipartimento Fis, I-34127 Trieste, Italy.
41Bulgarian Acad Sci, Inst Nucl Res & Nucl Energy, Sofia 1784, Bulgaria.
42Univ Barcelona, ICCUB, IEEC UB, Barcelona 08028, Spain.
43Univ Bologna, INAF Trieste, Bologna, Italy.
44Univ Bologna, Dept Phys & Astron, Bologna, Italy.
|Online Access:||PDF Full Text (PDF, 2.5 MB)|
|Persistent link:|| http://urn.fi/urn:nbn:fi-fe2020120499486
|Publish Date:|| 2020-12-04
Aims: In the presence of a sufficient amount of target material, γ-rays can be used as a tracer in the search for sources of Galactic cosmic rays (CRs). Here we present deep observations of the Galactic center (GC) region with the MAGIC telescopes and use them to infer the underlying CR distribution and to study the alleged PeV proton accelerator at the center of our Galaxy.
Methods: We used data from ≈100 h observations of the GC region conducted with the MAGIC telescopes over five years (from 2012 to 2017). Those were collected at high zenith angles (58−70 deg), leading to a larger energy threshold, but also an increased effective collection area compared to low zenith observations. Using recently developed software tools, we derived the instrument response and background models required for extracting the diffuse emission in the region. We used existing measurements of the gas distribution in the GC region to derive the underlying distribution of CRs. We present a discussion of the associated biases and limitations of such an approach.
Results: We obtain a significant detection for all four model components used to fit our data (Sgr A*, “Arc”, G0.9+0.1, and an extended component for the Galactic Ridge). We observe no significant difference between the γ-ray spectra of the immediate GC surroundings, which we model as a point source (Sgr A*) and the Galactic Ridge. The latter can be described as a power-law with index 2 and an exponential cut-off at around 20 TeV with the significance of the cut-off being only 2σ. The derived cosmic-ray profile hints to a peak at the GC position and with a measured profile index of 1.2 ± 0.3 is consistent with the 1/r radial distance scaling law, which supports the hypothesis of a CR accelerator at the GC. We argue that the measurements of this profile are presently limited by our knowledge of the gas distribution in the GC vicinity.
Astronomy and astrophysics
|Type of Publication:||
A1 Journal article – refereed
|Field of Science:||
115 Astronomy and space science
The financial support of the German BMBF and MPG, the Italian INFN and INAF, the Swiss National Fund SNF, the ERDF under the Spanish MINECO (FPA2015-69818-P, FPA2012-36668, FPA2015-68378-P, FPA2015-69210-C6-2-R, FPA2015-69210-C6-4-R, FPA2015-69210-C6-6-R, AYA2015-71042-P, AYA2016-76012-C3-1-P, ESP2015-71662-C2-2-P, FPA2017-90566-REDC), the Indian Department of Atomic Energy, the Japanese JSPS and MEXT, the Bulgarian Ministry of Education and Science, National RI Roadmap Project DO1-153/28.08.2018 and the Academy of Finland grant nr. 320045 is gratefully acknowledged. This work was also supported by the Spanish Centro de Excelencia “Severo Ochoa” SEV-2016-0588 and SEV-2015-0548, and Unidad de Excelencia “María de Maeztu” MDM-2014-0369, by the Croatian Science Foundation (HrZZ) Project IP-2016-06-9782 and the University of Rijeka Project 184.108.40.206.02, by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, the Polish National Research Center grant UMO-2016/22/M/ST9/00382 and by the Brazilian MCTIC, CNPq and FAPERJ.
© MAGIC Collaboration 2020. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.