A personal view

on the global future

of TeV γ ray astronomy and Japan

Tadashi Kifune

world-wide collaboration andfuture of Japan/CANGAROO ?

TeV gamma rays from nearby galaxies

World-wide collaboration ? • Better sensitivity by (1-2?) orders of magnitude requires worldwide efforts to be combined a larger number of IACTs 　 to cover a larger area

wider energy region to cover • the role of small group (like CANGAROO) ?• “Collaboration and competition” : Multiple independent efforts • Ground –based observation: north-south, ……

“In the long-term, the collaboration should 　 be extended

to coordinate the observation 　 program taken with facilities

located at 　 different latitudes or longitudes.” (AGIS document)

World-wide efforts for several observatories: CTA, AGIS, ….. 　　　

What is going on …… in Japan• To join wider international collaboration. “Expression of interest” :

in the CTA meeting at the beginning of this year…….. “MOU with AGIS” : to be discussed

• Repairing work of CIII telescope several developing works of technology• Vision in the long term : scientific goal, concept, way of collaboration 　

　 “The direction to be taken” not made clear yet, ………

generally in whole of the society, • Various reformations going on: rapid change, in dismay, …….

universities, 　“ funding system”, “Academy of Japan Science”, ……

ICRR: (neutrino, cosmic rays ------ CANGAROO, Tibet, TA gravitational wave) …..

Aim of , and, lessons from CANGAROO--- from past to future ----

• The aim was to uncover a wealth of Galactic sources in the southern sky limitation of apparatus / surrounding conditions the Woomera site nearly at the sea level • Plastic mirrors : chosen for its weight less than glass but not with very good PSF, reflectivity, • “extended emission ” of Galactic sources to see with the CANGAROO imaging Cherenkov telescope• To scan the Galactic disc : need wider FoV

What sort of science is to be aimed in the next step ?

Apparatus may not have been well matched with the Galactic sources aimed,

Detection system in the next step ?

Current status of ~70 sources

Flux in 10-12 cm-2 s-1 TeV-1 at 1TeV

？

The break-through of imaging Air Cerenkov Telescope

Δθ≈ 1o 0.1o

1st generation

ΔΩ~1msrArea >~105m2

aperture~10mΦ

to ~30mΦ (MAGIC and H.E,S.S.)

Ω~1sr like GLAST?

stereo~4 telescopes2nd generation

a number of telescopes

Activities of White Paper Team• Formation of six working groups:

-- Dark Matter, - Compact Galactic Objects, - Supernova Remnants and Cosmic Rays, - Extragalactic (Non Gamma-Ray Bursts), - Gamma Ray Bursts, - Technical Working Group.

• Solicitationf of contributions from astroparticle physics community:- Via email & special sessions on meetings (First GLAST Symposium,Feb. 2007 (Palo Alto, CF), APS Meeting, April 2007 (Jacksonville, FL)).

• Writing of White Paper in 2006 & 2007:- Executive summary (in progress).- Detailed discussion (largely finished).- Appendices (Glossary…, tbw).

Quantum gravity

……..

Structure formation

Extragalactic diffuse

Normal galaxy is no fun?

To clarify/understand “the Origin/nature of CRs”;

To explain cosmic ray spectra, To understand the knee,

to know the cut off energy of acceleration, propagation and confinement in the Galactic disk

to accumulate more number of SNRs, PWNe, XRBs….:

to understand better.

Any other route to take?

Implication of EGRET results on LMC and SMC :

CRs of our Galaxy are not of extragalactic origin

New insight from comparing the total emission from different galaxies

excluded

LMC

SMC

Galaxy verified

From A.Woflendale (Durham)

EGRET observation on SMC, LMC and M31

LMC 2 x 10-7 cm-2s-1 > 100 MeV SMC < 5 x 10-8 cm-2s-1 > 100 MeV M31 <1.8 x 10-8 cm-2s-1 > 100 MeV• LTeV ～ Legret ∙(100MeV/1TeV)(α-1) = Legret∙10-4(α-1)

α=2.2~2.6: power index of gamma ray spectrum ?

• TeV flux extrapolated from the EGRET α= 2.2 ～ 2.6: < 2x10-13 ～ 2x10-15 cm-2s-1 for M31 2x10-12~ 2x10-14 cm-2s-1 for LMC

With Sensitivity of 10-14~ 10-13 cm-2s-1,

Number of γ rays for>1TeV with 10km2 detection area

(10-14~ 10-13 cm-2s-1) x 10 km2 x 105 s (1days, ~10nights obs) ≈ 102 ~ 103 gamma rays

SN1987A in LMC <5x10-13cm-2s-1 (5TeV) <1037erg s-1 0.05Mpc CANGAROO

Whole of M31 <2x10-11cm-2s-1 <2x1039erg s-1 0.8Mpc VERITAS objects in M31 <3x10-12cm-2s-1 <3x1038erg s-1 0.8Mpc HEGRA M87 ~ 10-13cm-2s-1 3x1040erg s-1 16Mpc HESS Perseus cluster <(3-8)x10-12cm-2s-1 <(2-4)x1042erg s-1 75Mpc VERITAS ……………………………. ………. …….

Upper limits / flux from objects in nearby galaxies

Emission from a galaxy similar to the Milky Way Galaxy

• Emissivity q (photon Hatom-1 s-1 sr-1),

　　 size of Galaxy : a~10kpc :

Fin= qa : viewed from inside

• galaxy at distance D

Fout= qa3 D-2 : from outside

• Fout = (a/D)2 ・ Fin ~ 10-4 (D /1Mpc)-2 ・ Fin

FIGURE 3. EnergyBACK TO ARTICLE

                                                                           

 -ray flux per unit

2 x 10-8 cm-2s-1sr-1 for > 1TeV

2 x 10-9 cm-2s-1sr-1 for > 10TeV

Emission from a normal galaxy similar to the Milky Way Galaxy

EGRET: (1~3)x10-4cm-2s-1sr-1 (>100MeV)

ΔΩ= 0.1→ ~10-5 cm-2s-1

α= 2.2~2.6 → 2x10-10 ~10-12 cm-2s-1(>1TeV)

x 10-4 → 2x(10-14 ~10-16) cm-2s-1(>1TeV, 1Mpc)

Diffuse emission

HESS : 2x10-8cm-2s-1sr-1 (>1TeV) 　 and Milagro

ΔΩ= 0.1 ~ 0.01→ 10-9 ~10-10 cm-2s-1 (>1TeV)

x 10-4 → 2x(10-13 ~10-14) cm-2s-1(>1TeV, 1Mpc)

Summation of all Galactic sources

2.3 x 10-10 cm-2s-1( at 1TeV)

x (10-4 ~10-5) → 2x(10-14 ~10-15) cm-2s-1(>1TeV, 1Mpc)

>1TeV γ rays from nearby galaxies• LMC 10-12~ 10-14 cm-2s-1 extrapolated from EGRET

• “normal galaxies” (similar to Milky Way Galaxy) flux estimated from EGRET and HESS data:

10-13 ~10-16 cm-2s-1 at D = 1Mpc

10-14 ~10-17 cm-2s-1 at D = 3Mpc – more gamma rays from more massive galaxies– Milky Way Galaxy :1.4 x 1011 Msun, LMC :1.0 x 1010 Msun,

SMC :1.7 x 109 Msun– M31 (Andromeda) galaxy : 7 x 1011 Msun– SN explosion rate ,– Confinement time, ………..

• Starburst galaxy, active galactic nuclei of jet axis off line of sight, ….

galaxy nuclei having massive black holes

10-13 ~ 10-12 s-1cm-2 ?• M87 : D=16Mpc, time variable TeV gamma ray? 109 solar mass BH HESS: LTeV = 3 x 1040 erg s-1, F = 10-12 erg cm-2 s-1

• Blazars

current sourcesand flux from normal galaxies

X 10-12 cm-2 s-1 TeV-1 at 1 TeV

10-14

10-13

10-12

10-11

10 100 1000 104 105

E x

F(>

E)

[TeV

/cm

2s]

E [GeV]

Possible CTA sensitivity

Crab

10% Crab

1% Crab

GLAST

MAGIC

H.E.S.S.

E.F(>E) [TeV/cm2s]

AGN and pulsar physics

Exploring the cutoff regime in Galactic sourcesA deep look at

the TeV skyNormal galaxies at ~3Mpc

From W.Hofmann

M31

Sensitivity of Synoptic TeV Telescopes

Tibet

Milagro

HAWC

sHAWC

TibetMD

Whipple

ARGO

Crab

HESS/VERITAS

GLAST

M31

at ~3Mpc

(From G.Sinnis)

SNRs in LMC

6566676869707172

0 50 100 150

right ascension in minute

- de

clin

atio

n in

deg

ree

Scan of 5 degree x 5degree region is not an easy work However, ~30 SNRs and other interesting sources

LMC is expected to have the highest flux of TeV γ rays among nearby galaxies

To compare the morphology with what GLAST will soon provide at ~ 1GeV

0.01 0.1 1 10 100

in northern skyin southen sky

distance (Mpc)

Bri

gh

tne

ss

(B

ma

gn

itu

de

)LMC

M31(Andromeda)

M87

X 10

X 104

Expected flux of aTeV γ ray in 0th approximation (by assuming Brightness ~ TeV flux) flux ？ )

TeV gamma rays from normal galaxieswill tell us about ……

• Disc: matter, B, CR distribution• Σpoint sources SNR, PWN, …..• nucleus of galaxy : BH,……

• Ratio of disc emission to Σpoint sources Emax acc. e/p, TSN, E - δ (confinement time in disk), ….• Morphology of intensity and spectrum cosmic rays: propagation/balance against galactic structure

Propagation/confinement of CRs

• E-α ;α≈ 2.7 = (2.0 ~ 2.2) + δ 　　　　　 B / C • D ≈ Eδ by assuming T ~ dCR 2 / D • CR Anisotropy ≈ λ/ dCR ~ D ~ Eδ: not as

observed dCR : thickness of CR 　 distribution in Galactic disc • Dependence of TeV γ-ray emission on M? (M: total mass of galaxy)

summary 1: the high energy structure of “galaxy”?• Milky way Galaxy in comparison with other

nearby galaxies• L (Mgalaxy) ? L ~ M or M2 or …… • high energy non-thermal process of galaxies• Point sources / emission from disc ? e/p, anisotropy, reacceleration, ….

• Radiation from massive black hole at the center of the galaxy?• Contribution from DM ?

• CRs as high as 1020eV ? 10-100TeV

summary 2: perspective of “nearby galaxies”?

• M31 in the north and LMC in the south to begin with. the flux of 10-15~ 10-13 cm-2s-1 is expected → 10 ~ 1000 γ ray photons with (10km2 ・ 1day)

hopefully to detect galaxies of having active nucleus like M87 at <~10 Mpc • Galaxies at ~ 3 Mpc : △θ ~ 1 degree morphology of a galaxy

• galaxies at ~10 Mpc : detection area > 10km2

• several tens Mpc ~ the distance of GZK cut off

very Wide FoV : ~1 sr FoV

additional thoughts and a remark

Some sayings (in Japan) : “Too many captains for a boat,

the boat would go climbing up a mountain” “Chase for two rabbits, to lose the both” “ A hunter chases a deer, not seeing the mountain, not knowing where he is”

“Nearby normal galaxy” is a unique object That will combine the TeV γ ray study of

Galactic and extragalactic phenomena,and

will deepen our understanding of the origin of cosmic rays.

Intrinsic nature peculiar to Galactic / extragalactic sources

or Detection bias ?

• Galactic sources :

extended/affected by disk emission

serious background lights from bright area of the sky

subtraction by “on/off mode” of observation

• Extragalactic sources:

time variable emission

dark area of the sky

more phenomena still left as to be observed

Acceleration site

• Emax acc. ? : > 10TeV, many objects Wefel :“naked SN” 5 x 1013 eV ; Ptuskin SN1a, ib, II “SNR in wind” 4 x 1015 Hypernova

novae 2 x 1011 environmental conditions

• What is TSN ? : morphology, propagation a time for SNR to merge into interstellar space Likely to vary from object to object

　　 independent of E ? Really, TSN = 105 yrs ? What is interstellar space, bubble, …..?• Some “ideal” source ?• To scan all sources ?

Scenic vista of ground-based γ-ray astronomy, on speculation

2005

2010

2015

GZK cut off?

GRB?

How many GLAST sources?

Galactic Disc?

TeV γ-rays from

Extragalactic diffuse emission?:

Normal galaxies?

Absorption cutoffby Infrared radiation? PeV to EeV γ-rays

Advanced IACTsto further study these phenomena

Related events in other bands

to extend γ-ray horizon?

“cluster of galaxies”DM, dark energy

“pair halo”

Energy flow of 1020eV CRs• Flux of CRs >1020eV f = (0.5-5)x10-19cm-2s-1 (from all the sky) ≈ (one century ∙ 1km2)-1 = 10-19cm-2s-1

F=10 eV cm-2s-1 = 10-11 erg cm-2s-1

One 1020eV is equal to 108TeV photons,

giving/corresponding to TeV flux of ~ 10-11 erg cm-2s-1

if coming from only one source

• Number of sources F∙4πD2/L ~ 100 → 10-13 erg cm-2s-1

for D=100Mpc, L = 1040erg s-1

　 keV MeV GeV TeV PeV EeV ZeV

100

104

108

1012 Number of telescopes, field of view, ...

Glast

109 photons

103 photons 1 photons106 sources

~1 sources

AugerArea

S (m2)

IACT

Newton

Towards better sensitivity, more sources

Towards more energetic

several attractive directions

ChandraSuzaku

104 sources?

We are here

100

1000

10000

100000

1000000

1985 1990 1995 2000 2005 2010 2015 2020

Year

Inte

grat

ed A

pertu

re (k

m^2

*str*

year

)

Fly'e Eye

AGASA

HiRes

Auger(N+S)

EUSO

TA

Auger(S Only)

Horizon due to Absorption

γ+ CMB photon → e+ + e-

GZK??

Gamma rays from massive BH in the center of galaxy ?

• TeV Blazars Fx ≈ Fγ~10-11 ~10-10 erg s-1 cm-2

• Nearby galaxies Compact x-ray sources in the center of 21 out of 39

nearby face-on and spiral galaxies with available ROSAT HRI data, as to have 　　　

Lx (2-10keV) ~ 1038 ~ 1040 erg s-1 Fx (2-10keV) ~10-13 ~ 10-11 erg s-1cm-2 　　　　　　　　　　 from Colbert and Mushotzky, Ap J

(1999)

Fγ ~10-13 ~ 10-11 erg s-1cm-2 ??

Point Sources ?

• Anisotropy, magnetic field, distance, ….• “Micro anisotropy”?

8 doublets and 2 triplets

out of 92 events (> 4x 1019eV; AGASA, Fly’s Eye)

10-6 -10-5 Mpc-3 sources ; 1042-1043 erg s-1?

• If no anisotropy → Top-down mechanism?

Beyond the horizon?Propagation of gamma-rays 　 (α=2.0)

Distribution of photon number Energy

Hard spectrum In the region of 10~100 TeV

Large extension of angular size Depending on B, distance, ……

Point Sources ?

• Anisotropy, magnetic field, distance, ….• “Micro anisotropy”?

8 doublets and 2 triplets

out of 92 events (> 4x 1019eV; AGASA, Fly’s Eye)

10-6 -10-5 Mpc-3 sources ; 1042-1043 erg s-1?

• If no anisotropy → Top-down mechanism?

TeV gamma ray To solve the argued topics

of 1020eV CRs

Estimate by numerical calculation

• F(E) = 7.4 x 10-14 ∙ (LCR/1043 erg s-1)∙(d/10Mpc)-2 x (E/140TeV) -1/2 photons cm-2 s-1 ?

for E < me2/εCMB ~ 140TeV

　　　 ≈ 10-13 　 photons cm-2 s-1 for 10 TeV

from Ferrigno, Blasi, De Marco, Astroparticle Phys 23, 211 (2005)