DarkMatterSearchindwarfSpheroidalgalaxies

NagisaHiroshima(ICRR,KEK)and

MasaakiHayashida (Chiba.U),Kaz Kohri (KEK,SOKENDAI)

workinprogress(2017)

CTA-Japanworkshop2017

Contents:1. Introduction

2. Method

3. Prediction

4. Conclusion

motivationsforsearchingdarkmatterindwarfspheroidalgalaxies

HowcanwesearchDMindSph withcertaindensityprofile?

1

IntroductionDarkMattersearchindwarfspheroidalgalaxies

2

EvidencefortheDarkMatter1,LargeScaleStructure

2,RotationCurvesofGalaxies

3,Bulletclusters

Weneedsomethingwithlittleelectromagneticinteractions3

Ω"#ℎ%~0.258

Strategies:

DarkMatter StandardModelParticles

IndirectSearch

collider

directsearch

4

???

AdvantagesofCTA:DM+DM->(particlesintheStandardModel)

DM+DM->2𝜸

DM+DM->qq->π0+...-> 𝜸+...

DM+DM->W+W-

->µ+nµ+...-> 𝜸+...

DM+DM->l+ l-->l±+ 𝛾(CMB)->𝜸+...

5

withΔ𝜃~0.03 deg

Why‘TeV’?DMasathermalrelicofouruniverse:Ω"#ℎ%~0.258

𝑑𝑛"#𝑑𝑡 + 3𝐻𝑛"# =−< 𝜎𝑣 > (𝑛"#% − 𝑛"#,@A% )

3𝐻𝑛"#~ < 𝜎𝑣 > 𝑛"#% @thermalfreezeout(zf)

Ω"#ℎ% = 0.1< 𝜎𝑣 >

3×10E%F 𝑐𝑚I𝑠EKEK, < 𝜎𝑣 > ~

0.1TeV

E%

𝑛"#𝑠 ~

𝐻< 𝜎𝑣 > 𝑠 ∝ (< 𝜎𝑣 > 𝑇)EK

mDM/Tzf~20 − 30

𝜌"#𝑠 ∝ 𝑚"# < 𝜎𝑣 > 𝑚"#

EK ∝< 𝜎𝑣 >EK

conserved

6

gamma-rayflux:

source

γγ

γ observer

distance(D)Solidangle(∆Ω)

J-factor[GeV2/cm5]denserisbetter

7

target:dwarfspheroidalgalaxies(dSph)

Ackermannetal.,2014,arXiv 1310.0828

1, galactic center : J=1022-1024 ◎ , contamination△2, dwarf spheroidal : J=1017-1020 ○ , contamination○

galaxies (dSphs) 8

Methods

9

spatialextensionofdSphs

10

dSph observer

distance(D)Solidangle(∆Ω)

𝐽 = S 2𝜋 sin 𝜃 𝑑𝜃XYZ[

\S 𝜌"#% 𝑟 𝑑𝑠^_`

𝜌"#(𝑟) &extension𝜃𝑚𝑎𝑥 isderivedfromstellarkinematicsdataseeGeringer-Sameth etal.,2015(spherical)

Hayashietal.,2016(axisymmetric),etc.

****

𝜃𝑚𝑎𝑥: positionoftheoutermostmemberstar(O(1)degree )

WetakethedensityprofileofdSphs intoaccount

DMprofileofdSph𝜌"# 𝑟 =

𝜌\

𝑟𝑟d

e1 + 𝑟

𝑟df

gEef

generalizedNFW

∝ 𝑟Ee

∝ 𝑟Eg

𝑟d

2E(gEe)/f𝜌\

11stellarkinematicsdatagives(𝛼, 𝛽, 𝛾, 𝜌d, 𝑟d)

sourceselection

Draco

Leo2Coma

UMa2

log10(J[GeV2/cm5])

dSph ofGeringer-Sameth 2015intheNorthen sky𝜃 𝑚

𝑎𝑥[deg]

Targets:compact,densedSph

name ra[deg]

dec[deg]

dist[kpc]

𝜃𝑚𝑎𝑥[deg]

log10(J𝜃𝑚𝑎𝑥)[GeV2/cm5]

log10(J<0.5˚)[GeV2/cm5]

Draco 260 57.9 76 1.3 19.05 18.84

Coma 186 23.9 44 0.31 19.02 19.02

LeoII 168 22.2 233 0.23 17.97 17.97

UrsaMajorII

133 63.1 32 0.53 19.42 19.42

13(Geringer-Sameth etal.,2015)

Profiles:

14

Draco

Coma

Leo2

UMa2

3deg

3deg

3deg

3deg

𝜃𝑚𝑎𝑥

𝜃𝑚𝑎𝑥

𝜃𝑚𝑎𝑥

𝜃𝑚𝑎𝑥

Profiles:

15

Draco

Coma

Leo2

UMa2

3deg

3deg

3deg

3deg

𝜃𝑚𝑎𝑥

𝜃𝑚𝑎𝑥

𝜃𝑚𝑎𝑥

𝜃𝑚𝑎𝑥

Itisimportanttotakethesestructuresintoaccount.Then,whatkindofDMdowesearchinthesedSphs?

ParticlePhysicsModele.g.DM+DM->W+ +W-

E2dN/dE[GeV]

E[GeV]

mDM=1TeVmDM=10TeV

16

motivatedinWinoDMmodel

Conclusion

20

Conclusion

• CTAisverysuitablefordarkmatter(DM)search

• dwarfspheroidalgalaxies(dSphs)aregoodtargetsbecauseoftheirclearenvironments

• WeshouldbecarefulaboutthespatialstructureofdSphs whenwesearchDMinthosewithCTA

• CTAisexpectedtoreach<𝜎𝑣>~1022 − 1023cm3/swith50hobservationsfordSph DMsearch

21