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Searching for light dark matter particles.

Alexey Boyarsky

Ecole Polytechnique F´ ed´ erale de Lausanne Galileo Galilei Institute for Theoretical Physics May 13, 2010

Dark Matter in the Universe

Rotation curves of stars in galaxies and of galaxies in clusters Distribution of intracluster gas Gravitational lensing data

These phenomena are independent tracers

• f

gravitational potentials in astrophysical systems. They all show that dynamics is dominated by a matter that is not observed in any part of electromagnetic spectrum.

Stellar Disk Dark Halo Observed Gas M33 rotation curve

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 1

"Bullet" cluster

Cluster 1E 0657-56 Red shift z = 0.296 Distance DL = 1.5 Gpc

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 2

Cosmological evidence for dark matter

Universe at large scales is not completely homogeneous We see the structures today and 13.7

billions years ago, when the Universe was 380 000 years old (encoded in anisotropies

• f the temperature of cosmic microwave

background)

All the structure is produced from tiny

density fluctuations due to gravitational Jeans instability

In

the hot early Universe before recombination photons smeared

• ut

all the fluctuations

To explain the observed anisotropies we need DM particles that

started to cluster before recombination.

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 3

A few basic questions

Is evidence for DM convincing?

Yes

There are still other options nevertheless

Is DM made up of particles?

Plausible assumption .

But no hard evidence. More exotic possibilities such as primordial black holes or MACHOs are not completely ruled out

We will study the scenario of dark matter particle and its

consequences for particle physics.

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 4

Properties of a DM candidate

DM is not baryonic DM is not a SM particle (neutrinos could be but . . . ) Any DM candidate must be

– Produced in the early Universe and have correct relic abundance – Very weakly interacting with electromagnetic radiation (“dark”) – Be stable or cosmologically long-lived

There are plenty of non-SM candidates Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 5

Neutrino dark matter

DM particles erase primordial spectrum of

density perturbations on scales up to the DM particle horizon – free-streaming length λco

F S =

t v(t′)dt′ a(t′)

Comoving free-streaming is approximately equal to the horizon at

the time of non-relativistic transition tnr (whenp ∼ m)

Upper bound on neutrino

masses mν < 0.58 eV (WMAP+LSS, 95% CL).

Neutrinos are relativistic after recombination (znr < 850) Neutrino DM would homogenize the Universe at scales below

λco

F S > 1 Gpc. This contradicts to the observed large scale structure

and data on CMB anisotropies

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 6

Properties of a DM candidate

DM is not baryonic DM is not a SM particle (neutrinos could be but . . . ) Any DM candidate must be

– Produced in the early Universe and have correct relic abundance – Very weakly interacting with electromagnetic radiation (“dark”) – Be stable or cosmologically long-lived

There are plenty of non-SM candidates Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 7

Interactions of a DM candidate

DM interacts with the rest of the matter gravitationally Other possible interactions? It is possible that DM particles interact only in the early (very) hot

Universe with some unknown particles

To be produced from the SM matter the DM particles should interact It may be absolutely stable and interact with SM particles via

annihilation only: DM+DM→SM. . .

It may decay with very small rate, ensuring cosmologically long life-

time: DM→SM. . .

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 8

At what energies to look?

The model-independent lower limit on the mass of fermionic DM Tremaine, Gunn (1979) The smaller is the DM mass – the bigger is the number of particles

in an object with some velocity dispersion σ

For fermions there is a maximal phase-space density (degenerate

Fermi gas) ⇒ observed phase-space density restricts number of fermions

Objects with highest phase-space density – dwarf spheroidal

galaxies – lead to the lower bound on the DM mass m 300 eV

Active neutrinos with m ∼ 300 eV have primordial phase-space

density Q ∼ Qobs.

Neutrino DM abundance Ωνh2 = mν 94 eV ⇒ Active neutrinos cannot

constitute 100% of DM

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 9

Universal DM bound 2008

Gilmore et al. 2007-2008 Since 1979 a number of known

dwarf spheroidal galaxies more than doubled.

New

dSph’s are very dense Qobs = 104 − 105 M⊙ kpc−3[km s−1]−3.

Bound

• n

any fermionic DM improved to become mDM > 0.41 keV

Boyarsky, Ruchayskiy, Iakubovskyi’08 Can this bound be further improved?

Yes!

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 10

Sterile neutrinos: a minimal unified model

• f all observed BSM phenomena.

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 11

νMSM: all masses below electroweak scale

Just add 3 right-handed (sterile) neutrinos N I

R to MSM: Asaka, Shaposhnikov, PLB 620, 17 (2005)

LνMSM = LSM + i ¯ N I

R ∂

/ N I

R −

„ ¯ LαM D

αIN I R + MI

2 ( ¯ N I

R)cN I R + h.c.

«

10−6 10−2 102 106 1010 10−6 10−2 102 106 1010

t c u b s d τ µ ν ν ν N N N N N e

1 1 3 3 1 2 3

Majorana masses masses Dirac

ν

quarks leptons

2

N eV

The spectrum of the MSM

ν ν ν

2

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 12

νMSM: all masses below electroweak scale

A very modest and simple modification of the SM which can explain within one consistent framework . . . neutrino oscillations . . . baryon asymmetry of the Universe . . . provide a viable (warm or cold) Dark Matter candidate

This model may be verified by existing experimental

• technologies. It is importnat to confirm it or rule it out.

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 13

Window of parameters of sterile neutrino DM

Sin2(2θ) MDM [keV] 10-16 10-14 10-12 10-10 10-8 10-6 0.3 1 10 100 Ω > ΩDM Ω < ΩDM

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 14

Allowed range of parameters

Sin2(2θ) MDM [keV] 10-16 10-14 10-12 10-10 10-8 10-6 0.3 1 10 100 Ω > ΩDM Ω < ΩDM

L6 = 2 5 L6=70 N R P L6

max=700

B B N l i m i t : L

6 BBN

= 2 5 Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 15

Allowed range of parameters

Sin2(2θ) MDM [keV] 10-16 10-14 10-12 10-10 10-8 10-6 0.3 1 10 100 Ω > ΩDM Excluded from PSD evolution arguments

L6 = 2 5 L6=70 N R P L6

max=700

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 16

Primordial properties of super-WIMPs

Feeble interaction strength of super-WIMP DM particles means that

in general they have not an equilibrium primordial velocity spectrum

For

super-WIMPs primordial velocity spectrum carries the information about their production

In case of such DM particles free-streaming does not describe the

suppression of power spectrum

1x10-3 2x10-3 3x10-3 4x10-3 1 2 3 4 5 6 q2 f(q) q/T L= 2 L= 4 L= 6 L= 8 L= 10 L= 12 L= 14 L= 16 L= 25 0.1 1 1 30 1 10 Transfer function T(k) k [h/Mpc] L= 0 L= 2 L= 4 L= 6 L= 8 L= 10 L= 12 L= 14 L= 16 L= 25

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 17

Lyman-α forest and cosmic web

Image: Michael Murphy, Swinburne University of Technology, Melbourne, Australia

Neutral hydrogen in intergalactic medium is a tracer of overall matter

• density. Scales 0.3h/Mpc k 3h/Mpc

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 18

The Lyman-α method includes

Astronomical data analysis of quasar spectra Astrophysical modeling of hydrogen clouds N-body simulations of DM clustering at non-linear stage Solving numerically Boltzmann equations for SM in the early

Universe

Finding global fit to the whole set of cosmological data (CMB, LSS,

Ly-α), using Monte-Carlo Markov chains Main challenge: reliable estimate of systematic uncertainties

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 19

Lyman-α forest and warm DM

Previous works (Viel et al.’05-’06; Seljak et al.’06) put bounds on free-

streaming λF S 100 kpc (“WDM mass” > 10 keV)

Pure warm DM with such free-streaming would not modify visible

substructures

In Boyarsky, Lesgourgues, Ruchayskiy, Viel’08 we revised these bounds

and demonstrated that

Boyarsky+ JCAP’09; PRL’09

– The primordial spectra are not described by free-streaming – There exist viable models with the mass as low as 2 keV, consistent with the Lyman-α

1 keV/m

s

FWDM 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.2 0.4 0.6 0.8 1

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 20

Halo (sub)structure in CDM+WDM universe

work in progress Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 21

Halo (sub)structure in CDM universe

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 22

Halo (sub)structure in CDM+WDM universe

PRELIMINARY: Aq-A-2 halo in CDM and CDM+WDM simulations (Gao, Theuns, Frenk, O.R., . . . ) Simulated CWDM model (right) is fully compatible with the Lyman-α

forest data but provides a structure of Milky way-size halo different from CDM (left)

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 23

Searching for decaying dark matter

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 24

Decaying DM

DM with radiative signatures: DM → γ + ν, γ + γ, e+ + e− . . .

ν

Ns e± ν W ∓ γ W ∓

• (a)

ℓ ℓ ν p − k

• G

p γ k ˜ ℓ R

• (b)

˜ ℓ ˜ ℓ ν p − k

• G

p γ k ℓ R

Appears in many models:

Right-handed neutrino

Dodelson & Widrow’93; Asaka, Shaposhnikov et al.’05

Gravitino with broken R-parity

Takayama & Yamaguchi’00 Buchm¨ uller’07

Volume Modulus

Quevedo’07

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 25

Constraints from X-ray observations

DM decay should produce a line in X-ray spectra

• f

various

• bjects.

It should be visible against e.g power law spectrum of diffuse extragalactic background.

∆E E ∼    10−2 Galaxy cluster 10−3 Milky Way 10−4 dSph XMM/Chandra: ∆E/E ∼ 10−2 SPI: ∆E/E ∼ 10−3 Fermi: ∆E/E ∼ 10−1

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 26

Properties of decaying DM

The properties of decaying DM are much less studied. Crucial property: the flux from DM decay

FDM = Eγ mDM ΓMfov

DM

4πD2

L

≈ ΓΩfov 8π

• line of sight

ρDM(r)dr (z ≪ 1, Ωfov ≪ 1)

The flux FDM ∼

• ρDM(r)dr and NOT to
• ρ2

DM(r)dr, as in the case

• f annihilating DM.

The difference is HUGE. Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 27

Decay signal from MW-sized galaxy

Moore et al. 2005 Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 28

Annihilation signal from MW-sized galaxy

Moore et al. 2005 Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 29

Decay vs. annihilation

In the case of decaying Dark Matter

the signal, if detected, is easy to distinguish from astrophysical backgrounds

We have a lot of freedom in choosing

• bservation targets and, therefore, can

unambiguously check DM origin of a suspicious signal.

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 30

For decaying DM "indirect" search becomes very promising!

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 31

Search for decaying DM: main challenges

Control

• f

astrophysical and instrumental background

Reliable determination of dark

matter content of an object

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 32

SPI background subtraction

Find observation off-GC “close in time” Teegarden Watanabe 2006 Normalize by count rate of 198 keV (strong instrumental line)

• 0.001

0.001 0.002 0.003 50 100 150 200 250 Count rate [cts/sec/keV] E [keV] ON-OFF ON spectrum × 0.01

Hundreds

• f

lines cancel better than 1% by fixing only

• ne number

Line

at 511 keV remains visible at ∼ 50σ

No other lines

above 3 − 4σ

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 33

DM in Andromeda galaxy (2007)

0709.2301

0.1 1 10 13 60 1 5 25 DM column density (g/cm2) Off-center angle, arcmin K2 GFBG KING MOORE N04 NFW BURK KER M31A M31B M31C

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 34

Mass-to-light ratio in Andromeda galaxy?

Corbelli et al. A&A 2009 Chemin et al. ApJ 2009

Mass-to-light ratio of bulge and disk components vary by a factor ∼ 4

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 35

DM in Andromeda galaxy (2010)

Red W & D, M31b Green W & D, M31c Blue W & D, M31d Dashed Chemin09, ISO Dotted Corbelli09, R_B 28 kpc 5 10 15 20 r,kpc 100 1000 500 200 300 150 700 S_DM, M_Sunpc^2

Dark matter column density

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 36

DM distribution in individual objects

Knowledge of dark matter distribution in individual objects is crucial

for astrophysical searches of decay/annihilation signals

Dark matter column density is uncertain within a factor of few (much

more for R ρ2dl)

Uncertainty in modeling of the baryonic contribution Dwarf spheroidal galaxies PRL’06 Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 37

Universal properties of DM distribution

Fortunately, it is possible to minimize the dependence

• f the results on astrophysical uncertainties related to

individual objects.

One

can exploit a universal property

• f

DM distributions.

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 38

Constant surface density?

Kormendy, Freeman’94; Donato et al. 2009; PRL’06

Dark matter surface density remains for different types of galaxies?

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 39

An evidence in favor of MOND?

Gentile et al. Nature’09

Baryonic surface density for different types of galaxies.

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 40

Universal properties of DM distributions?

Going through the literature we collected a “catalog” of ∼1000 DM Boyarsky et al. 0911.1774

density profiles for ∼300 individual objects, ranging from dwarf spheroidal satellites of the Milky Way to galaxy clusters

Different methods (rotation curves, X-rays, weak lensing, . . .). Different

• bservational groups fit the mass distribution with different velocity

profiles (isothermal sphere, Navarro-Frenk-White, Burkert, . . .)

Important questions:

– What properties to compare? – Often fits to different DM density profiles exist for the same object. How to relate their parameters? – Any universality is observed?

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 41

Comparing DM density profiles

Fitting the same (simulated) data with two different profiles one

finds a relation between parameters of two DM density distribution, fitting the same data

0911.1774

5 10 15 20 r rc 4 6 8 10 12 vc2 a

– NFW vs. ISO : rs ≃ 6.1 rc; ρs ≃ 0.11 ρc – NFW vs. BURK : rs ≃ 1.6rB ; ρs ≃ 0.37ρB – For most

• bserved
• bjects

ρ⋆r⋆ = const

Observable not sensitive to the choice of dark matter density profile

– Dark matter column density S =

• l.o.s.

ρDM(r)dl ∝ ρ⋆r⋆

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 42

Observations vs. simulations

0911.1774 S changes slowly. There is a universal scaling.

1 2 3 4 5 6 107 108 109 1010 1011 1012 1013 1014 1015 1016 DM column density, lg (S/Msun pc-2) DM halo mass [Msun] Clusters of galaxies Groups of galaxies Spiral galaxies Elliptical galaxies dSphs Isolated halos from ΛCDM N-body simulations Subhalos from Aquarius simulation

S ∼

• Mhalo

≈0.2

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 43

Universal scaling of DM column density

0.5 1 1.5 2 2.5 3 3.5 107 108 109 1010 1011 1012 1013 1014 1015 1016 DM colum density, lg (S/Msun pc-2) DM halo mass [Msun]

The relation between S and Mhalo is observed for isolated halos of 0911.1774

all scales (for all observed halo masses from 108M⊙ to 1015M⊙).

Slope of subhalos (Aquarius simulation) is reproduced Median value and scatter coincide remarkably with pure DM

simulations.

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 44

Universal scaling of DM column density

0.5 1 1.5 2 2.5 3 3.5 107 108 109 1010 1011 1012 1013 1014 1015 1016 DM colum density, lg (S/Msun pc-2) DM halo mass [Msun]

No visible features – universal (scale-free) dark matter down to the

lowest observed scales and masses

No deviations from CDM down to Mhalo = 1010M⊙ new proof that dark matter exists! Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 45

Independent determination of mass

work in progress Rines & Diaferio 2006, 2010

1 2 3 4 5 6 7 107 108 109 1010 1011 1012 1013 1014 1015 1016 DM column density, lg (S/Msun pc-2) DM halo mass [Msun] Clusters of galaxies Groups of galaxies Spiral galaxies Elliptical galaxies dSphs Isolated halos, ΛCDM N-body sim. Subhalos from Aquarius simulation 1 2 3 4 5 6 7 107 108 109 1010 1011 1012 1013 1014 1015 1016 DM column density, lg (S/Msun pc-2) DM halo mass [Msun] M and S - caustics, clusters M and S - caustics, groups M - caustics, S - X-rays M - WL, S - WL M - WL, S - X-rays

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 46

Independent determination of mass

Mandelbaum et al. JCAP 8 (2008) 6

1 2 3 4 5 6 7 107 108 109 1010 1011 1012 1013 1014 1015 1016 DM column density, lg (S/Msun pc-2) DM halo mass [Msun] Clusters of galaxies Groups of galaxies Spiral galaxies Elliptical galaxies dSphs Isolated halos, ΛCDM N-body sim. Subhalos from Aquarius simulation 1 2 3 4 5 6 7 107 108 109 1010 1011 1012 1013 1014 1015 1016 DM column density, lg (S/Msun pc-2) DM halo mass [Msun] M and S - caustics, clusters M and S - caustics, groups M - caustics, S - X-rays M - WL, S - WL M - WL, S - X-rays Average data from WL

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 47

Direct astrophysical detection.

As column density does not vary too much, decaying DM produces

an all-sky signal with some hot spots.

Objects of different scales and nature can be used to put robust

bounds.

Ones a candidate line is found,

spacial distribution can be compared with DM column density map.

DM origin can thus be unambiguously checked.

For decaying DM "indirect" search becomes "direct" !

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 48

Example: Spectral feature in Willman 1

2 3 4 5 2×10−5 4×10−5 6×10−5 Photons cm−2 s−1 keV−1 Energy (keV)

[Loewenstein & Kusenko [0912.0552]]

2.3 2.35 2.4 2.45 2.5 2.55 2×10−5 4×10−5 6×10−5 line flux line energy

+

min = 7.030788e+02; Levels = 7.053788e+02 7.076888e+02 7.122888e+02

68%, 90% and 99% confidence intervals

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 49

Dark matter decay signal

If the signal found in Willman 1 is due to DM decay – we expect

detectable signals from other objects.

Decay flux is proportional to average DM column density within

the FoV: S =

• l.o.s.

ρDM(r)dl

Expected flux from another object:

FX = FWil 1 × SX SWil 1

(Signal/Noise) ∝ SX ×

• Time · Area · Ωfov · ∆E

= ⇒ XMM-Newton usually provides an improvement in (Signal/Noise)

Collection area of EPIC cameras ∼ 4 times larger; FoV ∼ 13′

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 50

Observational targets

∆(Signal/Noise) ∝ SX SWil 1 ×

• Time × Area × Ωfov × ∆E

DM

content in Willman 1 (adopted in

[Loewenstein & Kusenko’09])

SWil 1 ≃ 210M⊙ pc−2

This estimate is based on [Strigari et al.’08] In [arXiv:1001.0644] we used this estimate to be

conservative

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 51

DM in Willman 1

Strigari et al.’08

Uncertainty in SWil 1 is factor 2-3; for Ursa Minor SUMi changes by about 50% (within 90%CL).

The one-parameter fit assuming the relation between the NFW parameters predicted by the ΛCDM N-body simulations

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 52

Observational targets

50 100 150 100 200 300 400 500 600 SMW Msun/pc2 Fornax Willman 1 M31 Sculptor

Objects for which archival data is available (used in

[arXiv:1001.0644]) Fornax dSph (XMM)

SF = 54.4M⊙ pc−2

Sculptor dSph

(Chandra) SSc = 140M⊙ pc−2

Andromeda galaxy (M31) : 90M⊙ pc−2 < SM31 < 600M⊙ pc−2 Milky Way : 70M⊙ pc−2 SMW 95 [Boyarsky et al. PRL’06; A&A’07] Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 53

DM in Dwarf Spherodiadals

DM content in “classical” dSphs is much more certain. Very low diffuse emission in X-rays. Not much baryons. Classical dSphs – preferred

• bservational targets.

[Boyarsky et al. PRL’06] Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 54

Checking for DM line in dSphs

Eline = (2.51 ± 0.07) keV

2.44 keV − 2.58 keV (1σ) 2.30 keV − 2.72 keV (3σ)

Line flux FWil 1 = (3.53 ± 1.95) × 10−7 photons/cm2/sec (68% CL) No significant lines were found in spectra of dSphs We obtain the following exclusions

2.44 − 2.58 keV 2.30 − 2.72 keV Fornax dSph: 5.1σ 3.3σ Sculptor dSph: 3.0σ 2.5σ Fornax + Sculptor 5.9σ 4.1σ

In case of the DM decay origin of the line we were expecting about 4σ detection

from Fornax. However adding the line makes fit worse.

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 55

DM in Andromeda galaxy (2008)

Boyarsky, O.R. et al. MNRAS’08

4x101 4x103 1x102 1x103 2 4 6 8 10 12 14 16 18 20 10 20 30 40 50 60 70 80 DM column density [MSun/pc2] Off-center distance [kpc] Off-center distance [arcmin] Widrow Dubinski (2005) M31B

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 56

Checking for DM line in M31

Exclusion from 2.44 − 2.58 keV 2.30 − 2.72 keV Fornax + Sculptor dSph: 5.9σ 4.1σ

Andromeda galaxy

Diffuse spectrum above 2 keV is a featureless power law MNRAS’08 [0709.2301]

2.44 − 2.58 keV 2.30 − 2.72 keV M31, 1kpc < R < 3kpc: 22.7σ 20.1σ M31, 5 kpc off-center: circle radius 3 kpc 10.4σ 10.4σ M31, both regions 24.9σ 23.3σ

1001.0644 Extremely significant exclusion from central 8 kpc of Andromeda! All bounds are based on the conservative DM estimate from [Widrow & Dubinski’05]! Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 57

DM in Andromeda galaxy (2010)

Boyarsky, O.R. et al. MNRAS’08 Chemin et al. 0909.3846 Corbelli et al. 0912.4133 Kusenko & Loewenstein 1001.4055

4x101 4x103 1x102 1x103 2 4 6 8 10 12 14 16 18 20 10 20 30 40 50 60 70 80 DM column density [MSun/pc2] Off-center distance [kpc] Off-center distance [arcmin] Widrow Dubinski (2005), M31B Chemin et al. (2009), ISO Corbelli et al. (2009), rB = 28 kpc Maximum disk, Kerins et al.’00

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 58

New data and mass-to-light ratio in M31

Burkert profile Stellar disk M/L = 8

Chemin et al. Corbelli et al.

Corbelli et al. A&A 2009 [0912.4133] Chemin et al. ApJ 2009 [0909.3846]

– New precise HI data resolve features within inner 5–8 kps – Chemin et al. model this region – Corbelli et al. exclude this region from the analysis

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 59

DM in Andromeda galaxy

4x101 4x103 1x102 1x103 2 4 6 8 10 12 14 16 18 20 10 20 30 40 50 60 70 80 DM column density [MSun/pc2] Off-center distance [kpc] Off-center distance [arcmin] Widrow Dubinski (2005), M31B Chemin et al. (2009), ISO Corbelli et al. (2009), rB = 28 kpc Maximum disk, Kerins et al.’00

Bounds in [arXiv:1001.0644v1] are from 1–3 kpc and 2–8 kpc (based on

the model by [Widrow & Dubinski’05]

To be conservative in the final version we repeat the analysis for [Corbelli et al.’09] and added data from 10-20 kpc. Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 60

Checking for DM line in M31

Exclusion from Fornax and Sculptor dSphs:

2.44 − 2.58 keV 2.30 − 2.72 keV 5.9σ 4.1σ

Exclusion from central 8 kpc of Andromeda:

2.44 − 2.58 keV 2.30 − 2.72 keV DM model 24.9σ 23.3σ

[Widrow & Dubinski’05]

7.9σ 6.9σ

[Corbelli et al.’09] 1001.0644 Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 61

Summary of exclusions

68% CL: 2.44 keV − 2.58 keV 99%CL: 2.30 keV − 2.72 keV

“Consensus model”

(Widrow & Dubinski, M31B)

Minimal DM amount

(Corbelli et al., Burkert profile, rB = 28 kpc, M/L = 8)

68%CL 99%CL 68%CL 99%CL

M31 within 8 central kpc

24.9σ 23.3σ 7.9σ 6.9σ

M31 10–20 kpc off-center

12.0σ 10.7σ 11.7σ 10.6σ

All M31 obs.

28.2σ 26.2σ 13.6σ 13.2σ

All M31 + Fornax

29.0σ 26.7σ 15.2σ 14.0σ

The DM origin of the spectral feature in Willman 1 at ∼ 2.5 keV is

excluded with 14σ significance!

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 62

Restrictions on sterile neutrino DM

Boyarsky et al. MNRAS-2008

10-30 10-25 10-20 10-15 10-10 10-5 100 101 102 103 104 sin2 (2θ) Ms [keV] XMM Chandra HEAO-1 SPI (INTEGRAL) MW M31 MW

Galactic center

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 63

Restrictions on life-time of decaying DM

Boyarsky+ : XRB HEAO-1 2005; Bullet cluster Chandra 2006; LMC XMM MW XMM 2006-2007 MW Chandra Riemer- Sørensen+.; Abazajian+ 2007 M31 Watson+ 2006; Boyarsky+ 2007 dSps(UMi, Draco,W1, Sc, Forn), Suzaku, Chandra, XMM Boyarsky+ 2006,2010; Loewenstein, Kusenko 2008-2009

Life-time τ [sec] MDM [keV] 1025 1026 1027 1028 1029 10-1 100 101 102 103 104 XMM, HEAO-1 SPI τ = Universe life-time x 108 Chandra

PSD exceeds degenerate Fermi gas

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 64

Window of parameters of sterile neutrino DM

Sin2(2θ) MDM [keV] 10-16 10-14 10-12 10-10 10-8 10-6 0.3 1 10 100 Ω > ΩDM Ω < ΩDM

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 65

Window of parameters of sterile neutrino DM

Boyarsky, Ruchayskiy et

• al. 2005-2008

Sin2(2θ) MDM [keV] 10-16 10-14 10-12 10-10 10-8 10-6 0.3 1 10 100

Excluded from X-rays

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 66

Window of parameters of sterile neutrino DM

Boyarsky, Ruchayskiy et

• al. 2005-2008

Sin2(2θ) MDM [keV] 10-16 10-14 10-12 10-10 10-8 10-6 0.3 1 10 100

Excluded from X-rays

Excluded from PSD evolution arguments

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 67

Window of parameters of sterile neutrino DM

Boyarsky, Ruchayskiy, Lesgourgues, Viel [0812.3256] Boyarsky, Ruchayskiy, Shaposhnikov [0901.0011]

sin2(2θ1) M1 [keV] 10-15 10-14 10-13 10-12 10-11 10-10 10-9 10-8 10-7 10-6 5 50 1 10 ΩN1 < ΩDM Phase-space density constraints X-ray constraints ΩN1 > ΩDM

L6=25 L6=70 N R P L6

max=700

BBN limit: L6

BBN = 2500

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 68

Window of parameters of sterile neutrino DM

Boyarsky, Ruchayskiy, Lesgourgues, Viel [0812.3256] Boyarsky, Ruchayskiy, Shaposhnikov [0901.0011]

sin2(2θ1) M1 [keV] 10-15 10-14 10-13 10-12 10-11 10-10 10-9 10-8 10-7 10-6 5 50 1 10 ΩN1 < ΩDM Phase-space density constraints X-ray constraints ΩN1 > ΩDM

L6 = 2 5 L6=70 N R P L6

max=700

BBN limit: L6

BBN = 2500

Sterile neutrino is still viable and very attractive DM candidate. The

νMSM should be verified.

To explore the allowed window, more theoretical efforts, both on

particle physics and astrophysics sides, and new methods of analysis of the full set of the cosmological and astrophysical data is needed.

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 69

New mission: EDGE/XENIA

Spectrometers with big FoV and

spectral resolution better than 10−3 are needed

Future

missions (XEUS

• r

Constellation X) will have better spectral resolution but very small FoV

XENIA

(former EDGE), proposed for NASA’s Cosmic Origins by the team from NASA/MSFC, INAF , SRON + ISDC, EPFL,. . . ).

• ART−X

Spectrometer @ 1 keV EDGE Low−Energy @ 6 keV EDGE wide FoV

A.Boyarsky, et

• al. (2007)

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 70

Improved bounds on DM decay

Sin2(2θ) Ms [keV] P r

• b

e d b y X E N I A 10-16 10-15 10-14 10-13 10-12 10-11 10-10 10-9 10-8 10-7 2 5 50 1 10 100 Ω

s

> Ω

D M

Ω

s

< Ω

D M

Excluded from Lyman-α analysis Excluded from X-ray observations

Sin2(2θ) Ms [keV] P r

• b

e d b y X E N I A 10-16 10-15 10-14 10-13 10-12 10-11 10-10 10-9 10-8 10-7 2 5 50 1 10 100 Ω

s

> Ω

D M

Ω

s

< Ω

D M

Excluded from Lyman-α analysis Excluded from X-ray observations

Sin2(2θ) Ms [keV] P r

• b

e d b y X E N I A 10-16 10-15 10-14 10-13 10-12 10-11 10-10 10-9 10-8 10-7 2 5 50 1 10 100 Ω

s

> Ω

D M

Ω

s

< Ω

D M

Excluded from Lyman-α analysis Excluded from X-ray observations

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 71

THANK YOU FOR YOUR

ATTENTION

Alexey Boyarsky SEARCHING FOR LIGHT DARK MATTER PARTICLES. 72