T HE 3.5 KE V C ANDIDATE DARK M ATTER D ECAY
S IGNAL - C URRENT S TATUS AND N EAR - FUTURE
P ROSPECTS
Jeroen Franse
Lorentz Institute & Leiden Observatory
IDM 2016, Sheffield, 20 July 2016
With
Alexey Boyarsky, Oleg Ruchayskiy, Dmytro Iakubovskyi,
Also see IDM talks/slides from Monday by
Michael Loewenstein and Kevork Abazajian
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| I NTRODUCTION
D ECAYING DARK M ATTER
WIMP S
SUPERWIMP S
Interaction strength at
weak scale
Interaction strength
weaker-than-weak
Correct ΩDM for masses
Gev – TeV
Correct ΩDM for masses
of order keV
Would have short
lifetime
Lifetime longer than
age of universe
Made stable with new
physics
Allowed to be decaying
DM
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| I NTRODUCTION
S TERILE N EUTRINOS IN X-R AYS
Decaying DM should decay into monochromatic X-rays
(see e.g. Dodelson & Widrow 93, Shi & Fuller 99, Abazajian et al. 01, Abazajian 05,
review: Drewes et al. 16)
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| I NTRODUCTION
TARGET S OURCES
Good targets are dark matter dominated. Specifically, sources
with high expected decay signal strength
signal ∝ DM mass in FoV / distance2
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| D ETECTIONS
D ETECTION AT ∼3.55 KE V IN A NDROMEDA (M31)
Boyarsky et al. 2014a [1402.4119]
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| D ETECTIONS
D ETECTIONS OF THE U NIDENTIFIED 3.5 KE V L INE
B OYARSKY ET AL . 2014 A , B [1402.4119,
M31 galaxy
Perseus cluster
Galactic center
XMM-Newton, center & outskirts
XMM-Newton, outskirts only
XMM-Newton, inner ∼ 50pc
B ULBUL ET AL . 2014, 2016 [1402.2301,
73 clusters
Perseus cluster
47 clusters
1408.2503]
4.4σ
5.7σ
1605.02034]
XMM-Newton (MOS & PN),
centers only, up to z = 0.4
Chandra, center only
Suzaku XIS, centers
5σ & 4σ
3.5σ
2σ
F RANSE ET AL . 2016 [1604.01759]
Perseus cluster
Suzaku XIS, center & outskirts
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∼7.6σ
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| L INE O RIGIN
I NSTRUMENTAL O RIGIN ?
Instrumental origin unlikely
1. Detected in 5 different detectors
XMM-Newton MOS and PN detectors
Chandra ACIS-S, ACIS-I
Suzaku XIS
2. Line redshifts correctly with sources
Clusters stacked in object restframe (Bulbul et al. 2014)
Line in Perseus redshifted correctly at ∼ 2σ
3. Not detected in blank sky dataset
16 Msec with XMM
∼8 Msec with Suzaku (Sekiya et al. 2015 [1504.02826])
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| L INE O RIGIN
ATOMIC L INE ?
Unlikely: can not explain consistently all observations
Bulbul et al. 2014
M31 line is stronger than other atomic emission
CLUSTERS
need anomalous line ratios of a factor ∼ 10 − 20
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| L INE O RIGIN | D ECAYING DM I NTERPRETATION
DARK M ATTER D ECAY ?
The line flux should be proportional to surface density
Perseus
M31
Boyarsky et al. 2014a [1402.4119]
Franse et al. 2016 [1604.01759]
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| L INE O RIGIN | D ECAYING DM I NTERPRETATION
DARK M ATTER D ECAY ?
Line flux, 10-6 photons cm-2 s-1
The line flux should be proportional to mass / distance2
GC
10
Perseus
27
τ DM
=
2
s
27
τ DM
1
Blank-sky
M31
0
x1
=
6
s
0
x1
τ DM
=
s
27
8
0
x1
τ DM
28
8
=
1.
s
0
x1
0.01
0.1
Projected mass density, MSun/pc2
Boyarsky et al. 2014b [1408.2503]
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| L INE O RIGIN | D ECAYING DM I NTERPRETATION
DARK M ATTER D ECAY ?
The line flux should be proportional to mass / distance2
Line flux, 10-6 photons cm-2 s-1
C AVEAT I – G ALACTIC C ENTER
GC
GC is an extremely complicated environment
10
Line
in GC might be Potassium
Perseus
(Riemer-Sorensen [1405.7943]; Jeltema & Profumo [1408.1699])
but not necessarily
27 s
M31
(Boyarsky et al. 2014b,c [1408.2503, 1408.4388])
27 s
27 s
2
28 s
=
0
0
1
1
10 is not inconsistent
M
x the GC
x
The important
thing
is
τD
x
8
6
8
=
=
1.
and potassium
cannot
explain
all observations
=
DM
DM
τ
τ
1
τ DM
Blank-sky
0
x1
0.01
0.1
Projected mass density, MSun/pc2
Boyarsky et al. 2014b [1408.2503]
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| L INE O RIGIN | D ECAYING DM I NTERPRETATION
S UBSEQUENT W ORKS
For review see ”A White Paper on keV Sterile Neutrino Dark
Matter” [1602.04816].
3.5 KE V LINE PRESENCE CONFIRMED
Jeltema & Profumo 2014, Urban et al. 2014, Carlson et al. 2014, Iakubovskiy et
al. 2015
N ON - DETECTIONS
Malyshev et al. 2014, Anderson et al. 2014, Tamura et al. 2015, Sekiya et al.
2015, Jeltema & Profumo 2016, Hofmann et al. 2016
A STROPHYSICAL ORIGINS
Jeltema & Profumo 2014, Carlson et al. 2014, Gu et al. 2015, Phillips et al 2015
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| L INE O RIGIN | D ECAYING DM I NTERPRETATION
S UBSEQUENT W ORKS
For review see ”A White Paper on keV Sterile Neutrino Dark
Matter” [1602.04816].
G U ET AL . 2015 [1511.06557] – Charge Exchange
3.5 KE V LINE PRESENCE CONFIRMED
Jeltema & Profumo 2014, Urban et al. 2014, Carlson et al. 2014, Iakubovskiy et
Colliding cold Hydrogen and hot Sulfur can emit a
al. 2015
3.48 keV line. Not resolvable in current detectors.
N ON
- DETECTIONS
Depends
on the amount of cold gas and velocity.
Malyshev et al. 2014, Anderson et al. 2014, Tamura et al. 2015, Sekiya et al.
2015, Jeltema & Profumo 2016, Hofmann et al. 2016
We have no current limits on CX. May be plausible in
clusters, not expected in dwarf galaxies.
A STROPHYSICAL ORIGINS
Jeltema & Profumo 2014, Carlson et al. 2014, Gu et al. 2015, Phillips et al 2015
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| L INE O RIGIN | D ECAYING DM I NTERPRETATION
C AVEAT II – P ERSEUS C LUSTER
Depending on mass model, 3.5 keV line is somewhat or much
brighter in Perseus than other objects.
10
Perseus
27
-6
Line flux, 10 photons cm s
-2 -1
GC
τ DM
=
2
x1
s
27
s
=
6
28
0
x1
τ DM
s
27
0
τ DM
1
M31
0
=
Blank-sky
8
τ DM
s
0
x1
8
=
1.
x1
0.01
0.1
2
Projected mass density, MSun/pc
However, single object analysis more sensitive to calibration
uncertainties (work forthcoming).
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| D RACO
D RACO DWARF GALAXY
We have been awarded 1.4 Ms of XMM observations of the
Draco dwarf galaxy
Highest expected signal of all dwarf galaxies
(Geringer-Sameth+ 2014, Lovell+ 2014)
Very gas-poor (do not expect any atomic lines)
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| D RACO
D RACO DWARF GALAXY
RUCHAYSKIY ET AL . 2016
[1512.07127]
low significance (2σ )
feature
consistent with DM
lifetime estimates
τDM > (7 − 9) × 1027 sec
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| F UTURE
N OW WHAT ?
H IGH SPECTRAL RESOLUTION WITH M ICROCALORIMETERS
Hitomi satellite, damaged but took some data of
Perseus (results coming soon)
Micro-X sounding rocket (Figuerao-Feliciano et al. 2015
[1506.05519])
Resolve atomic lines, measure velocity
shifts/broadening (e.g., Speckhard et al. 2016 [1507.04744])
S URVEY DATA
eRosita all sky survey
(all-sky) cross correlation techniques (Zandanel et al. 2015,
Franse in prep)
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| S UMMARY
S UMMARY
It’s very difficult to explain all detections and non-detections
simultaneously with conventional astrophysics or
systematics.
Decaying dark matter remains a plausible explanation.
Many more exotic DM models invoked in literature to explain 3.5 keV line.
Need higher spectral resolution, deeper observations, larger
samples and/or new techniques to resolve this question.
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BACKUP S LIDES
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D RACO BY P ROFUMO & J ELTEMA
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D RACO BY P ROFUMO & J ELTEMA
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P ERSEUS WITH S UZAKU
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A NDERSON , C HURAZOV & B REGMAN [1408.4115]
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PARAMETER S PACE
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