Probing Extreme Universe with Gamma-Ray, Kashiwa, January 13th

INDIRECT SEARCH FOR DM
CROSS-CORRELATION OF GALAXIESWITH EXTRA GALACTIC GAMMA-RAY

Masato Shirasaki (NAOJ)
Shun Horiuchi (Virginia)
Naoki Yoshida (U-Tokyo/Kavli IPMU)
References:	  Shirasaki,	  Horiuchi,	  NY,	  2014,	  PRD	  90	  35020	  	  	  	  Cosmic	  shear	  -­‐	  EGB	  Shirasaki,	  Horiuchi,	  NY,	  2015,	  PRD	  92	  12354	  	  	  	  LRG	  -­‐	  EGBThe	  success	  of	  ΛCDM	  conHnues…
lyman-­‐αgalaxies	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  clusters

CMBThe	  nature	  of	  dark	  maQer• Elementary	  parHcles	  ?	  
• ParHcle	  mass,	  charge,	  velocity	  dispersion	  • Cross	  secHon	  of	  (elasHc)	  scaQering	  • Cross	  secHon	  of	  self-­‐annihilaHon	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  • Decay	  life	  HmeThe	  key	  is	  non-­‐gravitaHonal	  signature,	  	  possibly	  electro-­‐magneHc	  one,	  of	  dark	  maQer.

Indirect search
fordark matterDirect	  mapping	  of	  dark	  maQer	  Small distortion of galaxy shapes → Grav. potential

Recent snapshot from HSC survey

When we have two maps…
Dark matter distribution
from CFHTLenS
surveyFermi all-sky γ-ray

M. Shirasaki(NAOJ)

S. Horiuchi(UC Irvine)

The first “cosmological” constraints
on the annihilation cross-sectionAll-­‐sky	  gamma-­‐ray	  map

Fermi sat.
Ackermann et al. 2014
Circles indicate the locations of 25 Milky Way satellite galaxies

AnnihilaHon	  cross-­‐secHon
Fermi 6-year data
Search for excess γ-emission
from dwarf galaxies↓No detection of excess↓
Modeling of DM contents↓Constraints on the DM
annihilation cross-section←

This	  is,	  however,	  a	  “local”	  constraint.

Dark matter distribution in a CFHT field
6 arcminColored by the number of source galaxies per grid
(grid size=0.15 arcmin)

Lensing analysis
Observation
inhomogeneous shear map

Ray-tracing simulation
homogeneous shear map
add noise

continuous NOT directly continuous
WL mass map compared! WL mass map
take up inhomogeneity

discard some pixels = paste mask fieldmasked WL map

statistics

masked WL mapShear -γ cross-correlation
Model prediction (template)

Astrophysical	  sources	  sub-­‐dominant	  at	  large-­‐angular	  scales	  for	  a	  canomical	  ann.	  cross-­‐sec8on

Shirasaki, Horiuchi, NY 2014

24 ﬁelds: 154 deg

CFHT-Fermi cross-correlation〈σv 〉

Shirasaki, Horiuchi, NY 2014, PRD

HSC	  0.5	  billion	  galaxies

Depth →

Euclid (2020-）

Dark matter, dark energy,
test of gravity

Area →

We’ll use HSC!!!

FORECAST

With LSST…
DETECTION with 3-5σ confidence is possible！！！

← This estimate isderived from the 4-yrFermi data
andthe current
SFG/blazer model.
Both can be improved.

All-sky simulation
Extra-galactic γ-ray (θpix ~ 0.2 deg) Weak lensing(θpix ~ 1 arcmin)

100 GeV, thermal crosssection bb channel

Many	  mock	  catalogues	  for	  Hyper-­‐Suprime	  Cam

X-correlation with LRGs
Expected	  signal	  from	  DM	  annihilaHon

DistribuHon	  of	  SDSS	  	  luminous	  red	  galaxies.	  
30,272	  LRGs	  with	  spectroscopic	  redshi_.	  
Well	  determined	  HOD	  with	  gal-­‐gal	  lensing	  info.	  
Plus	  many	  mock	  catalogues.

X-correlation with LRGs

Stacked	  γ-­‐image	  centered	  at	  the	  posiHon	  of	  the	  LRGs

Consistent	  with	  	  null-­‐correlaHon	  	  (〜	  No	  DM	  contribuHon)

Foreground	  and	  astrophysical	  sources
GalacHc	  model	  uncertainHes	  are	  unimportantγ-­‐ray	  from	  star	  formaHon	  	  in	  LRGs	  is	  unimportant

35	  models	  of	  pulsar/O-­‐star	  dist.,	  CR-­‐conﬁnement	  etc	  (galprop2012)	  +	  CR-­‐ray	  spectrum	  Cross-­‐secHon	  constraint↕

Uncertainty	  in	  clumping	  factor.

canonical	  thermal	  value

Shirasaki,	  Horiuchi,	  NY	  2015,	  PRD

So, with CTA…
Would	  it	  be	  feasible	  to	  do	  a	  “survey”	  	  	  	  with	  enough	  sensiHvity	  (@100GeV),	  	  	  2wide-­‐ﬁeld	  (tens	  of	  deg ),	  	  and	  with	  good	  angular	  resoluHon	  ?	  
If	  yes,	  we	  (I	  mean	  I)	  start	  thinking	  seriously	  about	  astrophysical	  sources.
(We	  can	  also	  do	  similar	  analysis	  to	  DM	  decay,	  by	  the	  way.	  
Very	  heavy	  DM	  decay	  might	  be	  a	  good	  target	  for	  CTA.)

Energy	  TomographyCross-­‐Power	  spectrum	  with	  2MASS	  galaxies	  (Ando	  2014	  JCAP)

DM	  decay	  lifeHme
1027	  1026	  	  [s]	  1025

10	  	  	  	  	  	  	  	  	  100	  	  	  	  	  	  	  	  	  1000	  	  	  [GeV]

Baring	  et	  al.	  201510	  	  	  	  	  	  	  	  	  	  	  100	  	  	  	  	  	  	  	  	  1000	  	  	  [GeV]