Study of the Galactic structure and halo dark matter by

Gravitational microlensing

Takahiro Sumi STE lab., Nagoya University

•Galactic haloGalactic halo

•Galactic centerGalactic center

Gravitational “Macro”lensing

Gravitational “Macro”lensing

Gravitational “Micro”lensing

starstar

observerobserver lenslens

distortion of space due to gravity distortion of space due to gravity

arcsec.arcsec. If a lens is a size of a star, elongation of images is an order of 100arcsec.

Just see a star magnified

Plastic lensPlastic lens

Single lensSingle lens

Application of Application of microlensingmicrolensing

Extra galactic 1,halo dark matter of lens galaxy(QSO variability）

Galactic 1,Galactic halo dark matter(towards the LMC ＆ SMC) 2,Galactic center structure (towards the Bulge)

3,exoplanet (towards the Bulge)

WMAP resultWMAP result

Dark Dark mattermatter DMDM=0.22=0.22 Baryon 4%:Baryon 4%:

Stars: 7%

Neutral gas: 2%

Cluster hot gas: 3%

Unknown (warm gas?): 88%

Dark energy Dark energy =0.74=0.74

BB=0.04=0.04

Galactic rotation curve & dark matter

Kepler: v2=GM/r

Dark Matter

M~3x1011M(R<100kpc)

Halo Dark Matter & Paczynski’s Idea 20〜 40 times more dark matter than visible mass.

MAssive Compact Halo Objects (MACHOs） WINPs

•MACHO can be observed by Microlensing.〜１０−６ need to observe 1M stars！

（ Paczynski 1986)

MACHO project (1990~2000)

12 million stars Mt. Stromlo 1.28m telescope

First Microlensing event by MACHO & EROS in 1993

results toward LMC

Tisserand et al.2006

MACHO 5.7 yrs: 12 events M~0.5M

16% of the mass of a Standard Galactic halo.

EROS 5yrs : 0 event

f<25% of the halo dark matter made of MACHO with 10-7-10 M

f< 10% for 3.5×10-7 -100 M

OGLE-II 4 year: 3 event (1 in SMC) f<20% for 0.4M

f<11% for 0.003-0.2M

OGLE-II (Wyrzykowski et al.2010)

That is:

• MACHOs are not major component of Galactic halo dark matter

MACHOs exist as many as visible objects!?

but

Degeneracy in parameters

tE RE (M,D)v t

Einstein crossing time ：

Bottom line:

• There are lens objects towards LMC

Are they really in the halo?

but

Halo Dark Matter?or

Self-lensing?

MEGAMEGA projectproject

results（ preliminary) ：

14 eventsf<30%

Andromeda galaxy （ M31 ）

Far side

SuperMACHO 4m telescope, 1/2 nights for 3 months over 5 years. ~30events

Center OuterCenter OuterE

vent

rate

Eve

nt ra

te

Halo MACHOHalo MACHO

Self-lensing in LMCSelf-lensing in LMC

results （ preliminary ）：25events (microling+SN)Self-lensing is negligiblef<30%

LMC

SuperMACHOv.s.

Super Nova

MOA (since 1995)

（ Microlensing Observation in Astrophysics）

（ New Zealand/Mt. John Observatory, Latitude： 44S, Alt: 1029m ）

If you want to visit NZ free, join to MOA If you want to visit NZ free, join to MOA contact: contact: sumi@stelab.nagoya-u.ac.jp

New Zealand

If you want to visit NZ free, join to MOA If you want to visit NZ free, join to MOA contact: contact: sumi@stelab.nagoya-u.ac.jp

MOA (until ~1500) （ the world largest bird in NZ）

height:3.5height:3.5 ｍｍweight:240kgweight:240kgcan not flycan not flyExtinct 500 years Extinct 500 years agoago

（（ MaoriMaori ate ate them)them)

MOA-II 1.8m telescope

First light: First light: 2005/32005/3Survey start:Survey start: 2006/42006/4

Mirror : 1.8mCCD : 80M pix. FOV : 2.2 deg.2

Observational targets

LMCLMC

50kpc50kpc

　　　　 event rate:event rate: LMC,SMC : LMC,SMC : ~2~2 events/yr (events/yr (~10~10-7-7 ))

Bulge : Bulge : ~500~500events/yr (events/yr (~10~10-6-6 ))　　　　 Planetary event : Planetary event : ~10~10-2-2

８８ kpc, GCkpc, GC

Observation towards LMC by MOA-II

~3obs/night~3obs/night

~10obs/night~10obs/night

Difference Image Analysis (DIA)

Observed Observed subtractedsubtracted

Dynamical constraint Dynamical constraint ((Carr & Sakellariadou ’99Carr & Sakellariadou ’99))

open & globular clusters open & globular clusters 10103 3 <M<10<M<1066

binary stars binary stars 101000 <M<10 <M<107 7

solar system objects 1010-3-3<M <M

impact on EarthEarth M<10M<10-13-13 halo halo M<10M<10-12 -12 disk disk

Requiring an universality of the Galaxy!Requiring an universality of the Galaxy!

Variability in lensed QSO Variability in lensed QSO EROS and MACHO (LMC)EROS and MACHO (LMC)

Schmidt et al ’98 Schmidt et al ’98 Excluded (in MExcluded (in M):):1010-7-7 <M< <M< 1010-1-1

Gravitational microlensingGravitational microlensing::

Other constraints on MACHOsOther constraints on MACHOs

Microlensing of QSOs

QSOmacrolens

microlenses

image A

image B

SUb-Lunar-mass Compact Objects (SULCOs)

-16 -14 -12 -10 -80

-1

-2

Log(M/Ms)

Log

CO

MACHOUnconstrained

CDM = SULCOs 10-16<M<10-7 ? Black hole annihilation

Current limit on compact objects Current limit on compact objects in universe from lensing studiesin universe from lensing studies

(1)microlensing of QSO Dalcanton, et al ’94(2,4)multiple image of compact radio sources.Wilkinson et al ’01 Augusto ’01 (3)multiple gamma-ray bursts Nemiroff et al ’01(5)multiple image of QSO Nemiroff 91

Constraint on MACHOs in cosmologyConstraint on MACHOs in cosmology

(10-13) <M<10-7 M

SUb-Lunar-mass Compact Objects

（ SULCO ）

planetesimal, PBH

MAssive Stellar-massCompact Objects

(MASCO)

102 <M< 104M

primordial stars, BH, PBH

Two windows

Summary 1

MACHOs are not major component of Galactic halo dark matter (<20%)

There are lens objects towards LMC

Are they really in the halo?MOA-II is trying to solve this problem

Two windows for MACHOs (SULCO, MASCO)

Galactic centerGalactic center

Galactic Bar

de Vaucouleur,1964, gas kinematicsBlitz&Spergel,1991, 2.4 IR luminosity asymmetryWeiland et al.,1994, COBE-DIRBE,confirmed the asymmetry.Nakada et al.,1991, 　 distribution of IRAS bulge starsWhitelock&Catchpole, 1992, distribution of MiraKiraga &Paczynski,1994 Microlening Optical depth

m

θ

8kpc

COBE-DIRBE Weiland et al.,1994, confirmed the asymmetry.

3030 l

all extinction correct disk subtracted

1010 b

Optical Gravitational Optical Gravitational Lensing ExperimentLensing Experiment

(OGLE)(OGLE)Las Campanas Altitude: 2300mSeeing ~ 1.3”

)'4270,'0029( ES

OGLE-I : 1991~1996 : 1m, 2kx2k CCD 19 eventsOGLE-II : 1997~2000 : 1.3m, 2kx2k CCD, 14’x14’ 500 eventsOGLE-III: 2001~ : 1.3m, 8kx8k mosaic CCD 600 events/yr : 35’x35’

Pieces of informationMicrolensing Optical depth, and Event Timescale, tE=RE/Vt, (Sumi et al.

2006)

Brightness of Red Clump Giant (RCG) and RRLyrae stars, (Stanek et al. 1997, Sumi

2004; Collinge, Sumi & Fabrycky, 2006)

Proper motions of RCG, (Sumi, Eyer & Wozniak, 2003; Sumi et al. 2004), Proper motion of 5M stars, I<18 mag,

~1mas/yr

1,the Galactic Bar structure

(face on, from North)

8kpc

G.C.Obs.

1,the Galactic Bar structure

(face on, from North)

8kpc

G.C.Obs.

1, 1, Microlensing Optical depth, Microlensing Optical depth, (Alcock et al. 2000; Afonso et al.2003; Sumi et al. 2003;Popowski (Alcock et al. 2000; Afonso et al.2003; Sumi et al. 2003;Popowski et al. 2004; et al. 2004; HamadacheHamadache et al. 2006;Sumi et al. 2006) et al. 2006;Sumi et al. 2006)

M=1.61010M,

axis ratio (1:0.3:0.2),

~20

2.Red Clump Giants Metal-rich horizontal branch stars Small intrinsic width in luminosity function (~0.2mag)

Stanek et al. 1997=20-30=20-30, axis ratio 1:0.4:0.3, axis ratio 1:0.4:0.3

RCG by IR (Babusiaux & Gilmore, 2005)

Deep survery by Cambridge IR survery instrument (CIRSI)

=225.5

3.Streaming motions of the bar with RCG

Sumi (Princeton) , Eyer (Geneva Obs.) & Wozniak (Los Alamos), 2003

Sun

faint

Vrot=~50km/s

Color Magnitude Diagram

Sumi, Eyer & Wozniak, 2003

bright

summary２All three results are consistent with the Bar with

M=1.61010M(Md=0.7x1010)

axis ratio (1:0.3:0.2) =20, (Han & Gould, 1995)

Vrot~50km/s •Little space for Dark Matter•Prefer Core than cusp dark matter (Binney & Evans 2001)

MOA-II constrain strongerρ r∝ -α

observation Halo+disk

Halo

disk

Dark matter density profile at center of galaxy & galaxy cluster ： Cusp: ρ r ∝ -1.5 or Core: ρ const∝ ？Simulation: Collisionless CMD reproduces nicely the observed large scale structure of the universe (r>>1Mpc)

NFW universal density profile ρ r∝ -1.5 with central cusp (Navarro, Frenk& White 1997)

Observation: rotation curve for CDM dominatedDwarf and low surface brightness (LSB)galaxieshigh surface brightness disc galaxies (Salucci 2001) have a density profile with flat central core.

Cusp-Core problem in cold dark matter (CDM) halo

Log(radius)

Log(

dens

ity)

Density profile of Milky way (Sofue et al. 2009)

disk

bulge

NFW(cusp)

Isothermal(core)

Burkert(core)

(Moore et al. 1999; de Blok et al. 2000; Salucci & Burkert 2000;Salucci&Martin 2009)

Dark halo density in ESO 116+G12Observed simulation (NFW)

Cusp-core problem in dwarf spirals to giant low surface brightness galaxies (CDM dominated in center)

rotation curve of dwarf spiral DDO47

Cusp (NFW)

Core

Prefer core

Lensing probability with image separation Δθ (Lin & Chen 2009)

Lensing image in 0047-281 (Koopmans 2003)

Observed galaxy subtracted

Cusp-core problem in giant elliptical galaxies;(Baryon dominated in center )

Core

Prefer cusp

Cusp, ρ r ∝ -1.9

Observation

Cusp (NFW)

Singular isothermal sphere

Cusp-core problem in giant elliptical galaxies & galaxy cluster;(Baryon dominated in center )

•Statistics of QSO multiple images(Wyithe Wyithe, Turner & , Spergel 2001; Keeton & Madau 2001;Li & Ostriker 2001; Takahashi & Chiba 2001)

•Arc statistics of clusters of galaxies(Bartelmann et al. 1998; Molikawa & Hattori 2001;Oguri , Taruya + Suto 2001, Oguri, Lee + Suto 2003)

•Time-delay statistics of QSO multiple images(Oguri, Taruya, Suto + Turner 2002)

X-ray observation of galaxy cluster

⇒ generally favor a steep cusp ( α ～ － 1.5)

Cusp-core problem:solutionSelf interacting dark matter(Spergel & Steinhardt 1999 ):σ/m~1cm2/g (10-(21−24) cm2 (Mx/GeV))make core and spherical halo(Yoshida etal. 2000)

Weaker interaction doesn’t work; largerinteraction leads to halo core collapse onHubble time (e.g., Moore et al. 2000, 2002; Yoshidaet al. 2002; Burkert 2000; Kochanek & White 2000)

Cusp-core problem: solution

Barion-CDM interaction (BCDMIs)•Dynamical friction of substructure (El-Zant et al.2001;Tonini et al., 2006;Romano-Diaz et al.2008)

•Stellar bar-CDM interaction (Weinberg&Katz, 2002;Holley-Beckelmann et al.2005)

•Baryon energy fedback(Mashchenko et al., 2006; Peirani et al. 2008)

Nonsingular, trancated isothermal sphere (NTIS) Cosmological, from collapsend virialization (shapiro et al. 1999; Iliev&Shapiro, 2001)

Explain core in rotation curves, but cannot explain the steep & cuspy center of massive galaxies favored by Lensing and X-ray observation (just seeing cuspy baryon?).

Mbulge=1.8x1010M, Rbulge=0.5kpcMdisk=7x1010M , Rdisk=3.5kpcTruncated Isothermal dark halo with h= 5.5kpc, vrot=200km/s

the Milky Way rotation curve (HI,CO,optical, VERA)

NFW(cusp)

Isothermal(core)

Burkert(core)

(Sufue et al. 2009)

Summary MACHOs are not major component of Galactic halo dark

matter (<20%) except two windows (SULCO, MASCO) but there are lens objects towards LMC, important for

astrophysical point of view

dark matter density profile in the galaxy may be core rather than cusp

microlensing contribute to constrain

Microlensing by SULCOs in Galactic halo

DM33 = 790kpc

Small source size 8*10-9 (star radius /106 km) arcsec

DLMC = 50kpc

M33

(Total event) ~103 for 10-8Ms, sec 　　　　　　　 ~1 for 10-11Ms , secFor 80hours obs. by SUBARU/Suprime-cam

A B

C D

MASCOs M=103 if MASCO=m

2.5mas

N=1.7(M/104)-1 mas-2 Inoue & Chiba ApJ ’03

Distribution of surface brightness

resolution＝ 0.025mas