A Northern Sky Survey for Both TeV CR anisotropy and -ray Sources

with Tibet Air Shower Array

Tibet AS collaboration

• The Tibet AS-gamma Experiment ;• Two Analysis Methods;• Preliminary Results;• Discussion and Conclusions.

2004.8 Zhang Yi Institute of High Energy Physics

Tibet Air Shower Array

– Located at an elevation of 4300 m (Yangbajing , China)

– Atmospheric depth 606g/cm2

– Wide field of view– High duty cycle (>90%)

3,600m2 (in area)Tibet-HD

3,600m2 (in area)

Tibet-III

Tibet-HD

Operation Time Live TimeAll Events

Mode Energy

Resolution (@3TeV) Area

Tibet-HD

1997.2~1999.9 555.9(mjds) 1.5×109 ~3TeV 0.9o 3600m2

Tibet-III 1999.11~2001.5 456.8(mjds) 5.5×109 ~3TeV 0.9o 22050m2

Tibet Air Shower Array

Method I -----Equal-zenith method

Zenith

North Pole

On-source

Off-source

6.8° ＜zenith<40.0° 　

10

10

1* i OFFBG

iN

N

, on onI N on

on

NI

Equal

, off offI N off

off

NI

Method II----Global CR. Intensity fitting method

2

, ,2, 2

2 2, ,

1

1

on on off i off ii i

t on

on on off i off ii i

N I N I

N I N I

2 2,

,total i t on

t on

I

Zenith

Tail-in and Loss-cone

DEC

RA.Duldig,PASA,Vol18,No.1

～±0.1%

Large scale anisotropy( method II)

Large scale anisotropy of diff. Data sample

Large scale anisotropy correction

σ=1.258

Before subtraction

After subtraction

σ=1.018

0

0

 

Sky Map

NO. R.A.(˚) DEC(˚) Signifi(σ) NO. R.A.(˚) R.A.(˚) Signifi(σ)

1 38.9 13.9 4.2 13 221.6 32.8 4.4

2 39.2 31.9 4.0 14 253.2 58.8 4.1

3 66.8 12.3 4.1 15 278.3 38.4 4.3

4* 70.1 11.9 4.6 16* 286.7 5.6 4.6

5 70.4 18.0 4.3 17 301.7 8.7 4.1

6 71.9 47.5 4.0 18* 304.3 36.7 4.2

7 78.9 18.9 4.2 19 309.5 49.1 4.4

8* 83.3 21.8 5.0 20 309.9 39.6 4.5

9* 88.8 30.2 5.6 21 318.0 40.6 4.7

10* 115.3 17.5 4.1 22 330.3 50.3 4.0

11* 165.5 38.4 5.3 23 333.0 34.7 4.0

12 199.9 29.7 4.0 24 336.9 12.7 4.0

Crab

Mrk421 List of sky cells with clustered directions (24)having statistic significance larger

than 4.0σ.

Discussion -----Hot Point (88.8-30.2)

SNR counterpart G179.0+2.6, RA : 88.42 DEC :31.08 Size (/arc min): 70 Type: Shell

3.7σ 4.5 σ

5.6 σ

b=+5˚

b=0˚

b=-5˚

b=+5˚

b=+5˚

b=0˚

b=0˚

b=-5˚

b=-5˚

Discussion -----Hot Point (304.3-36.7)

S.W. Cui and C.T. Yan,2003, in Proc. 28th International Cosmic

Ray Conference , 2315. 4 σ EGRET counterpart 3EG J2016+3657 RA :304.008 DEC : 37.2 Milagro (306.6,38.9) 4.2 σ (Atkins,R., et al 2004, ApJ, 608,680)

~0 σ

4.2 σ

b=+5˚b=0˚

b=-5˚

b=+5˚b=0˚

b=-5˚

b=+5˚b=0˚

b=-5˚

3.9 σ

4.4 σ

4.5 σ

2.9 σ

Discussion -----Is there any extended source?

4.2 σ 3.6 σ

3.9 σ 2.7 σ

b=+5˚

b=0˚

b=-5˚

b=+5˚

b=0˚

b=-5˚

b=+5˚

b=0˚

b=-5˚

b=+5˚

b=0˚

b=-5˚

Up flux limit ( method I)

Conclusions

• Large scale anisotropy of CR. intensity with a magnitude about 0.1% are observed in two dimensions in TeV energy range.

• Crab and Mrk421 are detected.

• No other significant point source is found and give a up-flux limit.

Discussion -----Hot Points

* S.W. Cui and C.T. Yan,2003,in Proc. 28th International Cosmic Ray Conference , 2315.

• Reported in ICRC2003 *;• In the galactic plane and have EGRET counterpart;• High significance in single HD data or TibetIII data.

(304.3, 36.7)-----4.2σ

(286.7, 5.6)-----4.6σ

Significances from certain sources

Ra. Dec. On -Off Off σ

286.7 5.6 3582 601858 4.6

70.1 11.9 4172 812202 4.6

115.3 17.5 4094 975237 4.1

83.3 21.8 5151 1067431 5.0

88.8 30.2 6104 1176317 5.6

304.3 36.7 4399 1170821 4.1

165.5 38.4 5761 1167762 5.3

Tibet Excesses

Ununiform of azimuthal distribution----in different phase

—Azimuthal correction —

Large scale anisotropy correction

----In different bin size

Bin size (degree)

RMS

MC data

AS gamma data

Significance in diff. bin size (MC data)

3-VS-4

6-VS-7

4-VS-5

5-VS-6

2

( , )

( , ) 1 ( , )

( , )k

s k krso rso

bI i j k

rsorso

N I i j w i jSmooth Signi

N w i j

Normalization and smoothing

If I (i ,j) is a complete solution, then const* I (i ,j) is also a solution.

—The Global fitting method—

rso =resolution

( , ) ( , ) / ( , )k k kw i j N i j I i j0.9deg.

1Ikeep Normalize

Intensity　distribution　for　different　belt　along　galactic　plane

Diff. of two method (Japan-China)

Compton-getting　effect

•Located at Fenton Hill, New Mexico at an elevation of 2630 m.

•80m x 60m x 8 m deep, 723 PMTs

MILAGRO Air Shower Array

Milagro Excesses

RA DEC Sigma Upper Limit (Crab)

0.3 34.3 4.7 0.84 37.8 6.7 4.0 1.8 43.6 4.8 4.1 2.0 49.1 22.5 4.0 0.87 79.9 26.8 4.9 0.97 83.6 22.0 6.3 NA (Crab) 166.5 38.6 5.8 NA (Mkn 421)306.6 38.9 4.2 0.78313.0 32.2 4.5 0.85339.1 72.5 4.2 3.02356.4 29.5 4.1 0.84

Atkins,R., et al 2004, ApJ, 608,680