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![Page 1: The Detection of an Unexplained Emission Line at 3.56 keV Esra Bulbul Harvard-Smithsonian Center for Astrophysics Maxim Markevitch (NASA/GSFC), Adam Foster.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f275503460f94c3f645/html5/thumbnails/1.jpg)
The Detection of an UnexplainedEmission Line at 3.56 keV
Esra BulbulHarvard-Smithsonian Center for Astrophysics
Maxim Markevitch (NASA/GSFC), Adam Foster (CfA), Randall Smith (CfA), Mike Loewenstein (NASA/GSFC), and Scott Randall (CfA)
![Page 2: The Detection of an Unexplained Emission Line at 3.56 keV Esra Bulbul Harvard-Smithsonian Center for Astrophysics Maxim Markevitch (NASA/GSFC), Adam Foster.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f275503460f94c3f645/html5/thumbnails/2.jpg)
Line Searches in X-ray Observations of Clusters Largest
gravitationally bound aggregations of hot ICM and DM
Gas is enriched mainly via SN explosions by metals produced by stars in galaxies
Weak emission lines are now being discovered through X-ray spectroscopy
Werner et al. (2006)
2A 0335+096
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Why Stacking?
73 galaxy clusters at their rest frame
Increased S/N 0.01 < z < 0.35 Smeared non-source
features, e.g. instrumental, background
XMM-Newton Stamp Images of 73 Galaxy Clusters
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Background Before Stacking
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Background After Stacking
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Detection of An Unidentified Emission Line
Flux: 4.0 ± 0.8 x 10-6 phts cm-2 s-1
Energy: XMM - MOSFull Sample
6 Ms
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with an Additional Gaussian Model…
XMM - MOSFull Sample
6 Ms
![Page 8: The Detection of an Unexplained Emission Line at 3.56 keV Esra Bulbul Harvard-Smithsonian Center for Astrophysics Maxim Markevitch (NASA/GSFC), Adam Foster.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f275503460f94c3f645/html5/thumbnails/8.jpg)
Detected in Independent PN Observations
XMM - PNFull Sample
2 Ms
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Detected in Fainter 69 Clusters
XMM - PNFull Sample
1.8 Ms
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Chandra ACIS-S 883 ks
Detected in Chandra Observations of the Perseus cluster
![Page 11: The Detection of an Unexplained Emission Line at 3.56 keV Esra Bulbul Harvard-Smithsonian Center for Astrophysics Maxim Markevitch (NASA/GSFC), Adam Foster.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f275503460f94c3f645/html5/thumbnails/11.jpg)
XMM-NewtonMOS
317 ks
Detected in XMM Observations of the Perseus cluster
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Confirmation
Boyarsky et al. (2014a, b) detected the line independent
XMM OFFSET observations of the Perseus cluster
M31Milky Way
Energy
Nor
mal
ized
Coun
t Rat
ecn
ts/k
eV/s
cnts
/keV
/s
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Unlikely Astrophysical Scenarios
K XVIII line at 3.52 keV
Atomic Database Estimates of K XVIII line at 3.52 keV and Ar XVII
DR line at 3.62 keV
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Unlikely Astrophysical Scenarios
K XVIII line at 3.52 keVAr XVII DR line at 3.62 keV
Atomic Database Estimates of K XVIII line at 3.52 keV and Ar XVII
DR line at 3.62 keV
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Unlikely Astrophysical Scenarios
K XVIII line at 3.52 keVAr XVII DR line at 3.62 keV
Atomic Database Estimates Ar XVII DR line at 3.62 keV
Based on Ar XVII triplet at 3.12 keV
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Unlikely Astrophysical Scenarios
K XVIII line at 3.52 keVAr XVII DR line at 3.62 keVEmission lines of strong
hydrogen- and helium-like ions
Atomic Database Estimates of K XVIII line at 3.52 keV and Ar XVII
DR line at 3.62 keV
![Page 17: The Detection of an Unexplained Emission Line at 3.56 keV Esra Bulbul Harvard-Smithsonian Center for Astrophysics Maxim Markevitch (NASA/GSFC), Adam Foster.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f275503460f94c3f645/html5/thumbnails/17.jpg)
Unlikely Astrophysical Scenarios
K XVIII line at 3.52 keVAr XVII DR line at 3.62 keVEmission lines of strong
hydrogen- and helium-like ions
Charge exchange
Atomic Database Estimates of K XVIII line at 3.52 keV and Ar XVII
DR line at 3.62 keV
![Page 18: The Detection of an Unexplained Emission Line at 3.56 keV Esra Bulbul Harvard-Smithsonian Center for Astrophysics Maxim Markevitch (NASA/GSFC), Adam Foster.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f275503460f94c3f645/html5/thumbnails/18.jpg)
Unlikely Astrophysical Scenarios
K XVIII line at 3.52 keVAr XVII DR line at 3.62 keVEmission lines of strong
hydrogen- and helium-like ions
Charge exchange Radiative recombination
continuum (RRC) feature
Atomic Database Estimates of K XVIII line at 3.52 keV and Ar XVII
DR line at 3.62 keV
![Page 19: The Detection of an Unexplained Emission Line at 3.56 keV Esra Bulbul Harvard-Smithsonian Center for Astrophysics Maxim Markevitch (NASA/GSFC), Adam Foster.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f275503460f94c3f645/html5/thumbnails/19.jpg)
Unlikely Astrophysical Scenarios
K XVIII line at 3.52 keVAr XVII DR line at 3.62 keVEmission lines of strong
hydrogen- and helium-like ions
Charge exchange Radiative recombination
continuum (RRC) featureAny Other Astrophysical
Explanations? Atomic Database Estimates of K XVIII line at 3.52 keV and Ar XVII
DR line at 3.62 keV
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What is the origin?
Could this be a sterile neutrino decay signature?
Warm dark matter candidate sterile neutrinos decay into an active neutrino and emission line
Neutrino Properties Mass = 2Eγ
Mixing angle
Mas
s (k
eV)
The diffuse X-ray background (Boyarsky et al. 2006), cluster X-ray (Boyarsky et al. 2006b), BMW (Boyarsky et al. (2007), M31 (Watson et al. 2006), the Tremaine-Gunn bound (Bode et al. 2001), and Fornax dwarf galaxy (Strigari et al. 2006)
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Sterile Neutrino vs Astrophysical Line?
Astro-HPerseus
1 Msνbar= 300 km s-1
νDM= 1300 km s-1
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Sterile Neutrino Abundance
Sterile neutrinos constitutes 19% of the dark matter (Shi & ∼Fuller 1999)
may also be produced by means that do not involve oscillations, such as inflaton or Higgs decay (Kusenko 2006; Petraki & Kusenko 2008). This detection is consistent with 100% of dark matter composed of sterile neutrinos produced by these mechanisms.
If generated via split seesaw mechanism, this detection indicates that 100% of dark matter composed of sterile neutrinos (Kusenko, Takahashi, & Yanagida 2010).
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If you do not want to wait for Astro-H
Alternatives for the Confirmation
Stacked Suzaku and Chandra Observations of large number of galaxy clusters – NASA/ADAP grant (PI: Bulbul)
Deep observations of dwarf spheroidal galaxiesStacked observations of more Local Group galaxies (cannot nail
it if it is a detector artifact)Deep Chandra observations of the Galactic Center
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Limits from Our Detections
10-11 Mixing angle
Mas
s (k
eV)
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Bright Clusters
MOS Observations of the Bright Clusters (Coma, Perseus, Ophiuchus, Centaurus)
Flux: phts cm-2 s-1
MOS Observations of the Perseus cluster
phts cm-2 s-1
MOS Observations of the Perseus cluster (core cut)
phts cm-2 s-1
not due to a dominant source in the sample, not a background or effective area feature
Δχ2 = 17.1 (1 dof)
Δχ2 = 15.7 (1 dof)