Tibet AS collaboration
description
Transcript of Tibet AS collaboration
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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
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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%)
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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
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Method I -----Equal-zenith method
Zenith
North Pole
On-source
Off-source
6.8° <zenith<40.0°
10
10
1* i OFFBG
iN
N
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, 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
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Tail-in and Loss-cone
DEC
RA.Duldig,PASA,Vol18,No.1
~±0.1%
Large scale anisotropy( method II)
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Large scale anisotropy of diff. Data sample
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Large scale anisotropy correction
σ=1.258
Before subtraction
After subtraction
σ=1.018
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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.
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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˚
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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
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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˚
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Up flux limit ( method I)
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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.
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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
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Significances from certain sources
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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
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Ununiform of azimuthal distribution----in different phase
—Azimuthal correction —
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Large scale anisotropy correction
----In different bin size
Bin size (degree)
RMS
MC data
AS gamma data
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Significance in diff. bin size (MC data)
3-VS-4
6-VS-7
4-VS-5
5-VS-6
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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
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Intensity distribution for different belt along galactic plane
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Diff. of two method (Japan-China)
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Compton-getting effect
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•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
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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