J/A+A/642/A190 Gal. Center MAGIC diffuse gamma-ray emission (MAGIC Coll., 2020)
MAGIC observations of the diffuse gamma-ray emission in the vicinity
of the Galactic Center.
MAGIC Collaboration, Acciari V.A., Ansoldi S., Antonelli L.A.,
Arbet Engels A., Baack D., Babic A., Banerjee B., Barres de Almeida U.,
Barrio J.A., Becerra Gonzalez J., Bednarek W., Bellizzi L., Bernardini E.,
Berti A., Besenrieder J., Bhattacharyya W., Bigongiari C., Biland A.,
Blanch O., Bonnoli G., Bosnjak Z., Busetto G., Carosi R., Ceribella G.,
Chai Y., Chilingaryan A., Cikota S., Colak S.M., Colin U., Colombo E.,
Contreras J.L., Cortina J., Covino S., D'Elia V., Da Vela P., Dazzi F.,
De Angelis A., De Lotto B., Delfino M., Delgado J., Depaoli D.,
Di Pierro F., Di Venere L., Do Souto Espineira E., Dominis Prester D.,
Donini A., Dorner D., Doro M., Elsaesser D., Fallah Ramazani V.,
Fattorini A., Fernandez-Barral A., Ferrara G., Fidalgo D., Foffano L.,
Fonseca M.V., Font L., Fruck C., Fukami S., Garcia Lopez R.J.,
Garczarczyk M., Gasparyan S., Gaug M., Giglietto N., Giordano F.,
Godinovic N., Green D., Guberman D., Hadasch D., Hahn A., Herrera J.,
Hoang J., Hrupec D., Huetten M., Inada T., Inoue S., Ishio K., Iwamura Y.,
Jouvin L., Kerszberg D., Kubo H., Kushida J., Lamastra A., Lelas D.,
Leone F., Lindfors E., Lombardi S., Longo F., Lopez M., Lopez-Coto R.,
Lopez-Oramas A., Loporchio S., Machado de Oliveira Fraga B., Maggio C.,
Majumdar P., Makariev M., Mallamaci M., Maneva G., Manganaro M.,
Mannheim K., Maraschi L., Mariotti M., Martinez M., Masuda S., Mazin D.,
Micanovic S., Miceli D., Minev M., Miranda J.M., Mirzoyan R., Molina E.,
Moralejo A., Morcuende D., Moreno V., Moretti E., Munar-Adrover P.,
Neustroev V., Nigro C., Nilsson K., Ninci D., Nishijima K., Noda K.,
Nogues L., Noethe M., Nozaki S., Paiano S., Palacio J., Palatiello M.,
Paneque D., Paoletti R., Paredes J.M., Penil P., Peresano M., Persic M.,
Prada Moroni P.G., Prandini E., Puljak I., Rhode W., Ribo M., Rico J.,
Righi C., Rugliancich A., Saha L., Sahakyan N., Saito T., Sakurai S.,
Satalecka K., Schmidt K., Schweizer T., Sitarek J., Snidaric I.,
Sobczynska D., Somero A., Stamerra A., Strom D., Strzys M., Suda Y.,
Suric T., Takahashi M., Tavecchio F., Temnikov P., Terzic T., Teshima M.,
Torres-Alba N., Tosti L., Tsujimoto S., Vagelli V., van Scherpenberg J.,
Vanzo G., Vazquez Acosta M., Vigorito C.F., Vitale V., Vovk I., Will M.,
Zaric D.
<Astron. Astrophys. 642, A190 (2020)>
=2020A&A...642A.190M 2020A&A...642A.190M (SIMBAD/NED BibCode)
ADC_Keywords: Gamma rays ; Galactic center
Keywords: gamma rays: general - gamma rays: ISM - Galaxy: center - cosmic rays
Abstract:
In the presence of a sufficient amount of target material, gamma 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 (PeVatron) at the center of our Galaxy.
We used data from 100hr observations of the GC region conducted with
the MAGIC telescopes over five years (from 2012 to 2017). Those were
collected at high zenith angles (58-70deg), 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.
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 gamma-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 20TeV 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.
Description:
Fig1_RelativeFluxMap.fits:
Sky map of the Gal. Center region in units excess counts over
irreducible background as observed with the MAGIC telescopes.
Fig1_TSMap.fits:
Sky map of the Gal. Center region in the test statistic value
representation. The map uses a Gaussian test statistic to represent
the smeared data and background model. Values can therefore be
interpreted as local significance of the excess, without trial
correction for the look-elsewhere effect.
profile.dat:
CR density profile obtained with MAGIC data. Mean cosmic ray density
above 10 TeV in eV/cm^3 computed from observed gamma-ray flux observed
in rings from the Gal. Center and the density of molecular gas based
on (Tsuboi, M., Handa, T., & Ukita, N., 1999ApJS..120....1T 1999ApJS..120....1T).
sedS.dat:
Spectral data points of the source components used in the likelihood
data analysis of the Gal. Center region given in the spectral energy
density (SED) representation.
table1.dat:
Best fit parameters and uncertainties of the cross-bin forward-folding
likelihood fit of the spectra of individual components. The models
used in the fit are either powwer law or power law with exponential
cut-off.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
profile.dat 39 6 CR density profile obtained with MAGIC data (Fig. 4)
seds.dat 171 7 Spectral data points of the source components
used in the likelihood data analysis of the
Gal. Center region given in the spectral energy
density (SED) representation (Fig. 5)
table1.dat 104 4 Best fit parameters of the cross-bin
forward-folding likelihood fit of the spectra
of individual components
list.dat 95 2 List of fits maps
fits/* . 2 Individual fits maps
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Byte-by-byte Description of file: profile.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 pc R Radial distance of bin center
5- 6 I2 pc dR Half width of bin
8- 17 F10.8 eV/cm3 wCR Cosmic Ray Energy Density
19- 28 F10.8 eV/cm3 E_wCR Cosmic Ray Energy Density error (upper value)
30- 39 F10.8 eV/cm3 e_wCR Cosmic Ray Energy Density error (lower value)
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Byte-by-byte Description of file: seds.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I5 GeV Emin Lower bin edge
7- 11 I5 GeV Emax Upper bin edge
13- 20 E8.2 eV/cm2/s F(SgrA*) Spectral Energy Density
22- 30 E9.2 eV/cm2/s E_F(SgrA*) Spectral Energy Density error (upper value)
32- 40 E9.2 eV/cm2/s e_F(SgrA*) [] Spectral Energy Density error
(lower value)
42- 45 F4.1 --- S(SgrA*) Statistical significance (in sigma unit)
47- 54 E8.2 eV/cm2/s F(G0.9) Spectral Energy Density
56- 64 E9.2 eV/cm2/s E_F(G0.9) Spectral Energy Density error (upper value)
66- 74 E9.2 eV/cm2/s e_F(G0.9) [] Spectral Energy Density error
(lower value)
76- 78 F3.1 --- S(G0.9) Statistical significance (in sigma unit)
80- 87 E8.2 eV/cm2/s ULF(G0.9) ? Spectral Energy Density upper limit
89- 96 E8.2 eV/cm2/s F(Arc) Spectral Energy Density
98-106 E9.2 eV/cm2/s E_F(Arc) Spectral Energy Density error (upper value)
108-116 E9.2 eV/cm2/s e_F(Arc) [] Spectral Energy Density error
(lower value)
118-120 F3.1 --- S(Arc) Statistical significance (in sigma unit)
122-129 E8.2 eV/cm2/s ULF(Arc) ? Spectral Energy Density upper limit
131-138 E8.2 eV/cm2/s F(CS) Spectral Energy Density
140-148 E9.2 eV/cm2/s E_F(CS) Spectral Energy Density error (upper value)
150-158 E9.2 eV/cm2/s e_F(CS) [] Spectral Energy Density error
(lower value)
160-162 F3.1 --- S(CS) Statistical significance (in sigma unit)
164-171 E8.2 eV/cm2/s ULF(CS) ? Spectral Energy Density upper limit
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Component name
10- 12 A3 --- Type Spectral type
14- 17 F4.2 10-25/eV/cm/s N Flux Normalizaion
19- 23 F5.2 10-25/eV/cm/s e_N [] Flux Normalizaion error (lower value)
25- 29 F5.2 10-25/eV/cm/s E_N Flux Normalizaion error (upper value)
31- 35 F5.2 10-25/eV/cm/s sN [] Flux Normalizaion systematic error
(lower value)
37- 41 F5.2 10-25/eV/cm/s SN Flux Normalizaion systematic error
(upper value)
43- 47 F5.2 --- I Spectral index
49- 53 F5.2 --- e_I [] Spectral index error (lower value)
55- 59 F5.2 --- E_I Spectral index error (upper value)
61- 65 F5.2 --- sI [] Spectral index systematic error
(lower value)
67- 71 F5.2 --- SI Spectral index systematic error
(upper value)
73- 76 F4.1 TeV E ? Cut-off energy
78- 82 F5.2 TeV e_E []? Cut-off energy error (lower value)
84- 88 F5.1 TeV E_E ? Cut-off energy error (upper value)
90- 93 F4.1 TeV sE []? Cut-off energy systematic error
(lower value)
95- 98 F4.1 TeV SE ? Cut-off energy systematic error
(upper value)
100-104 F5.2 --- S Statistical significance (in sigma unit)
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 22 I3 --- Nx Number of pixels along X-axis
24- 26 I3 --- Ny Number of pixels along Y-axis
28- 30 I3 Kibyte size Size of FITS file
32- 56 A25 --- FileName Name of FITS file, in subdirectory fits
58- 95 A38 --- Title Title of the FITS file
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Acknowledgements:
Christian Fruck, cfruck(at)ph.tum.de
(End) Patricia Vannier [CDS] 15-Jul-2020