A search for a contribution from axion-like particles
to the diffuse background in the keV band
utilizing the Earth's magnetic fieldwith Suzaku/XIS observation
Ryo Yamamoto, Noriko Y. Yamasaki, Kazuhisa Mitsuidsa, (ISAS/JAXA)
andMasahiro Takada (IPMU)

yamamoto@astro.isas.jaxa.jp

International workshop on "Axion physics and dark matter cosmology”20-21 Dec 217 @ Osaka University

“Background” spectrum for DM search in keV bandSpeciﬁc Intensity[Counts cm 2 s 1 sr 1 keV 1]

Dark matter density: Milky Way < Galaxy < Cluster of galaxy
Hot plasma: Milky Way < Galaxy < Cluster of galaxy
10
10
10
10
10

6
5
4
3
2

10
1
10

Sekiya 2015

-1

1

0.5
XDB

2
M31 center

510Energy [keV]
Perseus center

Figure 3.1 Specific intensities of the typical XDB (Yoshino et al., 2009), the centerof the M31 and the Perseus cluster (Tamura et al., 2009) in the 0.5 – 12.0 keV range.
Note that detector responses are not convolved.
International workshop on "Axion physics and dark matter cosmology”20-21 Dec 217 @ Osaka University

2

Energy [keV](3’ 3’)(3’ 3’)
Sensitivity of DMXDB
search
inM31
keV
bandPerseus (3’ 3’)

Line Detection Limit
Dark Matter Column Density[LU / M pc −2]

Figure 3.5 3σ line detection limits for various targets (the XDB, the M31 and the′Perseus)the Suzaku
XIS,Way
3′ × 3<ofGalaxy
FoV and <100Cluster
ksec of exposure
time. LU (LineDarkmatterwith
density:Milkyof galaxy
−2 −1
−1
Unit)
is
equal
to
photonscmssr
Hot plasma: Milky Way < Galaxy <. Cluster of galaxy

Suzaku/XIS 100ksec

1

10

10

-1

-2

Sekiya 2015-3

10 0.5

1
XDB (3’ 3’)

2
M31 (3’ 3’)510Energy [keV]
Perseus (3’ 3’)

Figure 3.6 Same as Figure 3.5 but for 3σ line detection limits normalized by theircolumn densities.
International workshop on "Axion physics and dark matter cosmology”20-21 Dec 217 @ Osaka University3

Understandingof “background
Emission”
Understanding X-ray
diffuse background(XDB)

ysical size, density, and distance of HTC.

n the study of this thesis, “SWCX+LHB”+“Galactic absorption”×(“MWH” + “CXB”

X 線背景放射の正確なモデル化“HTC”) is applied as the model of XDB emission for ALPs search.
XDB model

3

Intensity [Counts cm-2 s-1 sr-1 keV-1]

10Page 15 of 93 1

Astron Astrophys Rev (2015)
23:1
Total

SWCX+LHB
MWH
合計
CXB
(a)
2

(b)

(1)+(2)
(3)
(4)

10

AGN

1

10

CXB ﬂux is resolved ~ 80 %.

CXB:~85%は点源に分解されている

0

10

10-1

Star

GalaxyΓ~ 1.4

0.7

1

2

5

Energy [keV]

Fig. 6 5Cumulative number10
counts for the 4 Ms CDF-S in the a 0.5–2 keV and b 2–8 keV bands. The total
2
52
11
Brandt&Alexander
5 Figure 3.2 Typical
10
photonEnergy
spectrumof X-raydiﬀusethat detector
numbercountsemission.
(black) have Notebeen apportioned
by source class, as labeled, into AGNs
(blue), galaxies (red),
(keV)
XDB
components
and stars(green).
bottom portions of each panel show the fractional contributions of each source classresponse function, andenergy resolution are
not
taken
into The
account.
光子エネルギー[keV]
2015
Brandt&Alexander
to the cumulative number counts. Note that AGNs remain the numericallydominant source population 2015

5

down to faint fluxes, although at still-fainter 0.5–2 keV fluxes galaxies will become numerically dominant.
Solar Wind Charge Exchange+ LocalHotreach
Bubble(kT~the0.1
keV)−2 at
The AGN
number counts≈ 14, 900 deg
faintest
0.5–2 keV fluxes, and this is the highest
陽圏中性物質との電荷交換反応によるX
線放射
sky density of reliably identified AGNs found at any wavelength. Taken from Lehmer et al. (2012)
Milky Way Halo (kT ~ 0.2 keV)
り巻く局所的な高温プラズマバブル(kT = 0.1 keV) pointからのX
線放射
Cosmic X-ray Background (extragalactic
sources)

り巻く高温プラズマハロー (kT = 0.2these
keV)
からの
X 線放射
methods
includeAlexander et al. (2005a), Brusa et al. (2010), Laird et al. (2010),

Xue et al. (2011), Lehmer et al. (2012), Civano et al. (2012), and Wang et al. (2013).
河核からの
X 線放射
International
workshop on "Axion physics and dark matter cosmology”20-21 Dec 217 @ Osaka University4

暗黒物質輝線探索に用いる/ 検出器の検討 X 線天文衛星 /暗黒物質輝線探索に用いる
用いる X 線天文衛星/ 検出器の検討 X 線天文衛星

observatories
Why X-ray
Suzaku?
Why Suzaku ?
hyComparison
Suzaku ? among「Chandra/ACIS」「XMM-Newton/PN, MOS」「すざく/XIS」の性能比較「Chandra/ACIS」「XMM-Newton/PN, MOS」「S」「XMM-Newton/PN, MOS」「すざく/XIS」の性能比較

14

dra/ACIS

3

Method to detect ALPs by X-ray observations

Table 3.1 Summary Chandra/ACISof orbit and CCD imaging
spectrometer on X-rayChandra/ACIS
observatories.
XMM-Newton/MOS+PN
Suzaku/XIS
XMM-Newton/MOS+PN
Suzaku/XIS

XMM-Newton/MOS+P
Suzaku(ISAS) (ESA)
Chandra(CXC)
XMM-Newton(ESA)! XMM-Newton
Suzaku(ISAS)
Chandra(CX
Suzaku(ISAS)
Chandra(CXC)
XMM-Newton(ESA)!
a (CXC)XMM-Newton(ESA)!
Suzaku(ISAS)
Chandra(CXC)
XMM-Newton
Suzaku(ISAS)
Chandra
(CXC)
(ESA)
!
CXC)
XMM-Newton!
Suzaku(ISAS)
Chandra(CXC)
XMM-Newton
(ES
2

[amin
]
4FI + 6BI) 視野~700
× (2MOS+ 1PN)

Satellite

00 (6BI)

8.3 × 8.3
× 2(2MOS+ 1PN)
17.8
17.8××(4FI(3FI++6BI)
1BI)視野~700[amin]

Suzakuエネルギーバンド[keV]
0.15 − 15

0.3−−12120.2

エネルギー分解能
50 − 200Orbit [eV]50−−200
200
50

[km]
2]
有効面積
@Perigee
1 keV[cm
800 (2MOS),
1200
(PN)

524
200(3FI),(4FI),320
400(BI)
(6BI)
660

17.8
17.8× ×(4FI(3FI+ +6BI)
1BI)
8.3 ×× 8.3

XMM-Newton0.2 − 12

0.15 − 15エネルギーバンド[keV]

0.3 − 12Chandra~700 × (2MOS + 1PN)
0.15 − 15

low earthエネルギー分解能
elliptical50
50 − 200 highly[eV]
50−−200
200highly elliptical 50 − 200
7.0
2] 10
800 (2MOS),
(PN)
有効面積
@ 1 keV1200
[cm×

3

13.2
× 10
660
(BI)
200(3FI),(4FI),320
400
(6BI)

3

800 (2MOS), 1200 (PN-2 s−1 sr[km]−2 keV−1] 110
Apogee531 NXB5 輝度
113.8
10−1/] 検出器の検討
135.7
× 10
-2 s
−1 sr−2 ×
NXB[cm− 1000
(不安定)
−X100
(不安定)
110
−−
101000
(安定)
不安定)
5 −輝度
(不安定)
− 10
(安定)
[cm
keV
(不安定)
5 −X100(不安定)
暗黒物質輝線探索に用いる
線天文衛星
索に用いる
X100線天文衛星/ 検出器の検討
暗黒物質輝線探索に用いる
線天文衛星

野の比較

Inclination [deg]
31.38
有効面積
× 視野の比較
輝度の比較
Period [min]NXB
95.19

3

3

66.17
76.9
NXB
輝度の比較
有効面積
× 視野の比較2861.593809.54N

XMM-Newton/2MOS
XMM-Newton/PNp

10

390 at 1.5 keV (BI)X 線背景放射

-1

2
5
1
2
10 10
5
NXB
1–10
光子エネルギー[keV]
光子エネルギー [keV]
Chandra/ACIS-I
XMM-Newton/2MOS
Suzaku/4XIS
Chandra/ACIS-I
XMM-Newton/2MOS
Suzaku/4XIS∗−2−1−2 XMM-Newton/PN
Chandra/ACIS-S
In unit of Chandra/ACIS-S
cm s srXMM-Newton/PN
keV−1 .

0.5

0.5
∗

1

p

有効面積 × 視野 [cm2 sr]

有効面積 × 視野 [cm2 sr]

1 10

0.2–12

6

0.1–15

0.5–12922 at-5 1 keV (2MOS)

380 at 4 keV

10

10

-4

1 10

X 線背景放射-11227
at 1 keV (PN)

10

0.5 0.5

1

1

2

2

5

5

5–100 光子エネルギー
10–1000
光子エネルギー
[keV]
[keV]

10

10

Chandra/ACIS-I
XMM-Newton/2MOS
Chandra/ACIS-I
XMM-Newton/2MOS
Suzaku/4XIS
Suzaku/4XIS
Chandra/ACIS-S
XMM-Newton/PN
Chandra/ACIS-S
XMM-Newton/PN

4p

輝度 [Counts cm 2 s 1 sr 1 keV 1]

10-4Energyrange [keV]
10
! 2"
10
Eﬀectivearea cm-5

輝度 [Counts cm 2 s 1 sr 1 keV 1]

5ー [keV]

輝度 [Counts cm 2 s 1 sr 1 keV 1]-1
輝線放射の計数を稼ぐために重要な性能である有効面積× 視野の面で10
めに重要な性能である有効面積× 視野の面で10-1
輝線放射の計数を稼ぐために重要な性能である有効面
10
ペルセウス銀河団中心10ペルセウス銀河団中心
10
5
5
5
CCD
name
XIS
MOS+PN
ACIS-I (FI)
10
10
は 10
XMM-Newton/PN
が最も有利
も有利
は XMM-Newton/PN
が最も有利
-2
-2
4
4 10
4
ACIS-S(FI/BI)
10 10
10
10
X 線背景放射の観測の障害となる非X 線バックグラウンド(NXB) の低害となる非 X 線バックグラウンド(NXB) の低X 線背景放射の観測の障害となる非X 線バックグラウ
333
アンドロメダ銀河中心
アンドロメダ銀河中心
-3
′
′
′-3
′
′
10
10
10
Field
17 .8 × 17 .8
30
indiameter16
×16
10 of view
102
さと安定性の面ではすざく/XIS
が最も有利
2
く/XIS が最も有利
さと安定性の面ではすざく/XISが最も有利102
10
10
6

6

10
1
10

-1

0.5

1

Suzaku/4XIS C
C

4

2
2
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I

>

5

Line Detection Limit [LU]

Strategy for DM search with X-ray satellite
10

XDB obs. (T=10 Ms) with 5 instruments

1
10
10
10

-1

-2

-3

0.5

2

5
10
Energy [keV]
Suzaku 4XIS Chandra ACIS-I XMM-Newton 2MOS
Chandra ACIS-S XMM-Newton PN

1Sekiya 2015

Figure 3.10 3σ line detection limits estimated from Eq.3.9 with the five CCD instrument observations of the XDB for 10 Msec of exposure time. The lowest cases for the
XMM-Newton and Chandra instruments are shown.

XDB + Suzaku/XIS is the best way!
International workshop on "Axion physics and dark matter cosmology”20-21 Dec 217 @ Osaka University

6

Axion Like Particle(ALP)-photon conversion: Pα→γ
ALP-photon conversion probability in a vacuum (van Bibber+ 1989)
L

✓

◆2

ga B? (t)cos (qL)
2 1
Pa! (q, t) =
2L
2
2
(qL)
✓
◆2
ga B? (t) L
qL < ⇡
2
q = m2 /2E
ma <

r

a

a

2⇡Ea
L

ma m
< a1 ⇥< 10

・ Pa→γ is simply proportional to (B⊥L)2

ga

6

eV

✓

Ea
keV

B?

：coupling constant◆ 12 ✓

L
104 km◆1
2(qL < π)・CAST experiment: B⊥ = 9.0 T, L= 9.26 m → B⊥L ~ 83 Tm (Arik+ 2014)
・Possible detection by a satellite observation using Earth’s magnetic fields is claimed
because a long line of sight with an order of the Earth’s diameter can compensate
the weak magnetic field (B⊥ ~ 30 μT) (Davoudiasl & Huber, 2006)
International workshop on "Axion physics and dark matter cosmology”20-21 Dec 217 @ Osaka University

7

Sola

Potential solar axion signatures with XMM-Newton
Fraser et al., 2014
・A seasonally varying X-ray background signal is observed.
・They conclude that this variable signal is consistent with the conversion of solar axions in
the Earth’s magnetic field.
・X-ray flux of 4.6 × 10−12 erg s−1 cm−2 deg−2 in 2–6 keV from geomagnetic conversion,
Solar axion signatures in XMM–Newton data

2149

Solar−1axion
in XMM–Newton
2157 has been interpreted.
which has 2.2 × 10−22 GeV
forsignatures
an axionmass indata
the μeV,
distribution differs between EPIC pn and EPIC MOS because of
their different out-of-field detector areas.
3.2 Results: EPIC pn
The EPIC pn in-orbit background has been very extensively studied (Lumb et al. 2002; Snowden et al. 2004; Rodriguez-Pascual &Gonzalez-Riestra 2008). The non-X-ray component has been simulated using the Monte Carlo package GEANT4 by Tenzer, Kendziorra& Santangelo (2008). The laboratory background of a pn-CCD
camera (actually, the focal plane sensor for CAST) is described byKuster et al. (2005).
In the past, EPIC MOS has been generally preferred for studiesof the extragalactic CXB, because of:

Blue: autumn

Downloaded from http://mnras.oxfordjournals.org/ at Uchu Kaga

Downloaded from http://mnras.oxfordjournals.org/ at Uchu Kagaku(a) the imperfectly-characterized charge transfer efficiency inindividual pn CCDs;(b) the factor ∼2 higher charged particle background in EPICpn;(c) the relatively small out-FOV pn detector area for the determination of the cosmic ray flux (Section 3.1.3).

Black: winterFigure 2. Schematics in the GSE noon-midnight plane of the orthogonal
GECOSAX scenario, of the XMM–Newton orbit (elongated ellipse) andof the Earth’s magnetic field, represented by field lines with McIlwain
L-values 5, 10 and 20 and by a parabolic approximation to the magnetopause.
The broken circle indicates the 40 000 km minimum altitude for XMM–
Newton observations. The shaded triangle indicates the allowed pointing
directions for XMM–Newton (approximately ±20o from perpendicular to
the Sun–Earth line); the triangle can ‘rotate’ about the X-axis (the Sun–
Earth line). X-ray conversion photons can enter the FOV of XMM–Newton
via various mechanisms, discussed in the text, shown schematically as (a)elastic scattering, (b) non-colinear conversion plus axion-to-photon backconversion, and (c) non-colinear conversion. Top: Winter configuration,2000 January 1. Bottom: Summer configuration, 2000 July 1.

Roncadelli & Tavecchio, 2015
Here, ・The
we are concernedwith possible
differencesan (2014) cannot be explained by this origin from the solar ALP.
resultin seasonal
Fraseret inal.
already faint diffuse signal, and the larger photon grasp of the EPIC
pn camera is the key parameter.
Fig. 14(a) shows the individual 2–6 keV X-ray spectra for spacecraft seasons A1–A4, integrated from 2000 to 12. The Winter spectrum A1 clearly lies below the other three, while A4 (Autumn)
is significantly higher than either A2 (Spring) or A3 (Summer).
Fig. 14(b) shows a typical result of randomizing10 the input observation files – i.e. randomly assigning the same observation files tofour new lists (A1∗–A4∗), each containing the same number of files
as the original A1–A4 (see Table 2).
For each spacecraft season, and for a common lowenergy correction for the absorbing Galactic hydrogen column(nH = 5 × 1020 cm−2 ), a power law of the form of equation (10b) was

・To preserve the momentum of the photon by the Primakoff process in case of relativistic
ALP, the XMM-Newton cannot observe because it never points toward the Sun.

probability
to ‘axion splitting’ ALP？
in a number ofInstrumental background depending on itsconversion
orbit?
orp dueanotherideal magnetic field geometries (infinitely thin solenoid, squarewell, Gaussian and δ-function) but not yet for the desired dipole ap-

International workshop on "Axion physics and dark matter cosmology”20-21 Dec
217 @to theOsaka
University
proximation
geomagnetic
field. It is thought here that isotropic8

Possibility to detect X-ray originating from ALP
When the lifetime decaying from DM to ALP is longer than age of the universe…
（Case-A）If ALP momentum is in the keV band, we can observe the single
depending on the Earth's magnetic field.
Additionally, in the case of the two-body decay…
（Case-B）If DM exists in the solar system neighborhood, the observed spectrum
shape is monochromatic. (e.g. Cicoli+ 2015)（Case-C）If DM is distributed over the universe uniformly, the observed spectrum
shape is continuum as a simple power-low (Γ = +0.5) created by thesuperposition of monochromatic lines with different cosmologicalredshifts. (e.g. Asaka+ 1998)
Dark Matter

ALP

photonObserverlifetime =τΦ
mass：mΦ

mass：ma ~ 0
momentum：mΦ/2

Geomagnetic field
momentum：mΦ/2International workshop on "Axion physics and dark matter cosmology”20-21 Dec 217 @ Osaka University

9

−0.2
0.6+0.3−0.3
0.8+0.4−0.4−0.02
1.50+0.02−0.02
1.35+0.02
−0.02

−0.2
8.2+0.2−0.2
7.3+0.2
−0.2

−0.2
+0.3
4.2−0.3
5.3+0.4−0.4(Case-B) Detection limit of monochromatic spectrum
0.99 (434)1–2012

2–2013

1.19 (434)emission measure of the optically-thin thermal CIE plasma integrated over the line of sight (the APEC model normalization):!
π) ne nH ds in units of 1014 cm−5 sr−1 , where ne and nH are the electron and the hydrogen density (cm−3 ).
temperature of the optically-thin thermal CIE plasma in units of keV.
abundances of Ne or Mg in units of the Solar-neighbor values given in Anders and Grevesse (1989).
photon index of the power-law model for the CXB component.
surface brightness of the CXB component (the power-law model normalization) in units of photons cm−2 s−1 sr−1 keV−1 at 1 keV (theon index is fixed at 1.4).
intensity of neutral oxygen (O I, centroid: 0.525 keV) in units of LU (photons cm−2 s−1 sr−1 ).

0.8

0.04

0.4

0.02

0

0

0.4

0.02

0.8

0.04

0.5

1

(b)

Local
Significance [ ](a)Line Intensity [LU]

・From the Suzaku archive, Sekiya+ 2016 selected 187 data sets of blank-sky
regions that were dominated by the X-ray diffuse background.
・Sekiya+ 2016 exhibited no significant detection of an emission line featurefrom dark matter.
・There is no feature on reported 3.5 keV line (e.g. Bulbul+ 2014).

0.5

No feature
Sekiya+ 2016
1

2

5
Energy [keV]12

5Energy [keV]

3
2
1
0.5

International
workshopon "Axion
physics
anditsdark
mattercosmology”20-21
Dec 217@ OsakaasUniversity
cted
DM line intensity,
its 1 σ statisticalerror
range and3 σ upper
limit.
The unit of line intensity
is defined“LU”, which is equal

10Possibility to detect X-ray originating from ALP
When the lifetime decaying from DM to ALP is longer than age of the universe…
（Case-A）If ALP momentum is in the keV band, we can observe the single
depending on the Earth's magnetic field.
Additionally, in the case of the two-body decay…
（Case-B）If DM exists in the solar system neighborhood, the observed spectrum
shape is monochromatic. (e.g. Cicoli+ 2015)（Case-C）If DM is distributed over the universe uniformly, the observed spectrum
shape is continuum as a simple power-low (Γ = +0.5) created by thesuperposition of monochromatic lines with different cosmologicalredshifts. (e.g. Asaka+ 1998)
Dark Matter

ALP

photonObserverlifetime =τΦ
mass：mΦ

mass：ma ~ 0
momentum：mΦ/2

Geomagnetic field
momentum：mΦ/2International workshop on "Axion physics and dark matter cosmology”20-21 Dec 217 @ Osaka University11(Case-C) Continuum created by cosmological redshift
When dark matter distributed over the universe uniformly is assumed, we observe
the continuum spectrum of the superposition of such monochromatic spectrum

Z

Pa!
I (E ) =⇢ dr ⇥ 2 (E (1 + z) m /2) [Counts s 1 cm 2 sr 1 ]l.o.s 4⇡mp✓◆
2 Pa! ⇢ 0m
1/2
f (x) = ⌦m0 + (1 ⌦m0 ⌦⇤0 ) /x ⌦⇤0 /x3
=
f
E
5/2
2E
⇡⌧ H0 m/ ga2

2

(B? L) E 1/2

1/2（Asaka+ 1998）

In order to search for X-ray continuous emission from ALP, we selected 4
observational targets from Suzaku/XIS archival data of XDB from 2005 to 2015.
Field name（Ra, Dec）

Number of observations

Exposure time

Lockman hole（162.9, 57.3）

9 times (every year)

542.5 ks

MBM16

（49.8, 11.6）

6 times (2012-2015)446.9 ks

SEP

（270.0, -66.6）

4 times (2009)

205.0 ks

NEP

（90.0, 66.6）

4 times (2009)204.2 ks

International workshop on "Axion physics and dark matter cosmology”20-21 Dec 217 @ Osaka University

12Spectral shapes of XDB and ALP
・We can estimated the surface brightness of ALP assuming the spectral shape.
・The emission model of CXB is represented by a power-law with its photon index of Γ = -1.4
(Kushino+ 2002) above 2 keV.
・The spectral shape of ALP is transcribed as a simple power-law function whose photon indexof Γ = +0.5 due to the effect of cosmological redshift (Asaka+ 1998).

Photons cm-2 s-1 keV-1

10-2

10-3

CXB（Γ ~ -1.4）

Data-NXBSWCX+LHB
CXB
MWH
ALP

-4
10We
plasmawouldlocal
like
to divide the XBD and ALP!

ALP

-5

10

(B⊥L)2

Γ = +0.5
10-6
0.7

1

2
Energy [keV]

5International workshop on "Axion physics and dark matter cosmology”20-21 Dec 217 @ Osaka University

13

Relation between Suzaku orbit and (B⊥L)2
9090

latitude [deg]

6060

③
3030
00

②

-30
-30

①
-60
-60

-90
-90
-180
-180

-90
-90

00

90
90

longitude [deg]

180
180

B⊥
Line of sight

・Suzaku goes round the earth in ~ 90 min, and an orbital plane changes.
・Transverse magnetic field along the line of sight, B⊥, changes with thesatellite motion relative to the Earth.
(B⊥L)2 changes depending on the observation time zone
International workshop on "Axion physics and dark matter cosmology”20-21 Dec 217 @ Osaka University

14

Classiﬁcation of dataset by (B⊥ L)2
Example of Lockman hole observation
6

50
50

6
1010

(B⊥L)2 [T2m2]

Exposure[ks]
Exposure Time time[ks]

１interval = 90 min
55
1010

44
1010

45

6 parts

40
40
35
30
30
25
20
20
15
10
10

Earth eclipse
33
1010

0

0

1

1

5
2

2

3

3

00

00

20000
2 104

Time [hour]

40000
4 104
2

60000
6 104

880000105

2 21100000
106⊥L)2 [T m2 ] 2(B(B⊥L) [T m ]・The location of Suzaku every 60 seconds for XDB observation
・B⊥, the transverse magnetic field along the line of sight estimated by IGRF-12・ (B⊥L)2 integrated to 6RE・Maximum: B⊥L ~ 300 Tm, Average: B⊥L ~ 140 Tm
International workshop on "Axion physics and dark matter cosmology”20-21 Dec 217 @ Osaka University

15

Observed spectrum (including detector response)
Consider systematic errors of CCD characterization and NXB ﬂuctuation (~ 30%)
-1

10

normalized counts s keV-1

CXB（Γ ~ -1.4）
Depending on observational direction

10

-2

-1

Exp.）Lockman hole

Data
NXB
SWCX+LHB
CXB
MWH
ALP

NXB
Normalization ﬂuctuation(B-3⊥L)2 class10

3 CCDs3 parts
local plasma

'

-4

10

0.7

ALP

1

Observation
9 times(B⊥L)2

SimultaneousΓfit= +0.5
with 68 dataset
2
Energy [keV]

5International workshop on "Axion physics and dark matter cosmology”20-21 Dec 217 @ Osaka University

16Surface brightness correlation between ALP and CXB
NEP

4

4×10−9Lockman hole

00

00

1

10−9

2

2×10−92

Surface brightness of ALP in 2−6 keV [erg/s/cm2/sr/104(Tm)2]3

3×10−9x10-92×10−93.5×10

x10-8

erg s

1

1.5-92 Surface brightness
2.5/sr] 2
of CXB in 2−6 keV [erg/s/cm
1 2.0
−8

1.5×10

x10
cm
sr

−8

2×10

−8

2.5×102(100 Tm)

-8
x10
3×10

3.0

−8

00
-2

−2×10

00

-2

−2×10−9-4−4×10−9

Surface brightness of ALP in 2−6 keV [erg/s/cm2/sr/104(Tm)2]2

2×10−924

2.8 ⇥ 10

3.5
9

−8

2×10

2.5×10
3×10
Surface brightness of CXB in 2−6 keV [erg/s/cm2/sr]

4×10−9

x10-9

3.0
−8

−9

2.5
−8

−9

Surface brightness of ALP in 2−6 keV [erg/s/cm2/sr/104(Tm)2]
Surface brightness of ALP in 2−6 keV [erg/s/cm2/sr/104(Tm)2][erg s-1 cm-2 sr-1 (100 Tm)-2 in 2-6 keV]

Surface brightness originating from ALP

x10-9

SEP

1.5

2.0

1.5×10−8
2×10−8
Surface brightness of CXB in 2−6 keV [erg/s/cm2/sr]

2.5

2.5×10−8

x10-8

MBM16

2.2

2.6

3.0

2.2×10−8 2.4×10−8 2.6×10−8 2.8×10−8
3×10−83.2×10−82Surface brightness of CXB in 2−6 keV [erg/s/cm /sr]

Surface brightness of CXB [erg s-1 cm-2 sr-1 in 2-6 keV]

3.4

3.4×10−8

International workshop on "Axion physics and dark matter cosmology”20-21 Dec 217 @ Osaka University

x10-8

17

ALP-photon coupling constant (continuum emission)
I(E ) / ga2

g↵2(B? L) E 1/2 (Asaka+ 1998)◆ 1⇣ m ⌘ 54 ✓◆1/2 ✓
B? L⌧
71< 4.4 ⇥ 10 GeV
10 keV
100 Tm
4.32 ⇥ 1017 s
✓
◆1/2✓
◆ 1/2
⇣
⌘
1/2
⇢
H0
f
2.20 ⇥ 10 18 s 1
1.92
1.25 keV cm 3f (x) = ⌦m0 + (1

10-6

Our result⌦⇤0 ) /x⌦⇤0 /x3

1/2

qL < ⇡10-8

QCD Axion

CAST

gaγγ [GeV-1]

⌦m0

10-10
10-12

ADMX

10-14
10-16 -8
10

Carosi+ 2013
10-6

10-4

10-2

ALP mass [eV]100International workshop on "Axion physics and dark matter cosmology”20-21 Dec 217 @ Osaka University

18

ALP-photon coupling constant (line emission)- Estimated Pa→γ for 187 observations (31 Ms) used by Sekiya+ 2016
- X-ray line detection limit by Sekiya+ 2016 converted into monochromatic
spectrum originating from ALP.
g↵

< 8.4 ⇥ 10 8 GeV 1 (1 < m < 14 keV)✓

B? L
140 Tm

◆ 1 ✓

Iline
0.02 L.U.

10-6

Our result

◆2

✓

⌧
4.32 ⇥ 1017 s

◆1/2

◆ 1/2

S
50 M pc 2
L.U. = photons s 1 cm 2 sr 1

qL < ⇡

10-8gaγγ [GeV-1]✓

QCD Axion

CAST
10-10
10-12

ADMX

10-14
10-16 -8
10

Carosi+ 2013
10-6

10-4

10-2

ALP mass [eV]100International workshop on "Axion physics and dark matter cosmology”20-21 Dec 217 @ Osaka University

19Summary
We proposed a novel method to uncover ALP origin photons by
space observatory using the Earth’s magnetic field in the X-ray
background.
The systematic uncertainty of NXB such as The NXB characterized
by the relative position of the earth and the satellite, and time
fluctuation from seconds to years are evaluated.
We did not detect any possible continuous emission from ALP.
In the keV band, we can search a unknown signature …
- Assuming of spectral shape- Depending the environmental parameter ( BL etc…)

International workshop on "Axion physics and dark matter cosmology”20-21 Dec 217 @ Osaka University

20