A Northern Sky Survey for
Both TeV CR anisotropy and -ray Sources
with
Tibet Air Shower Array
Hongbo Hu
([email protected])
For Tibet AS collaboration
• The Tibet AS-gamma Experiment ;
• Two Analyses Methods;
• Preliminary Results;
• Discussion and Conclusions.
2004.8
Institute of High Energy Physics
YangBaJing Observatory and
its Experiments
– Located at an elevation of 4300 m
(Yangbajing , China)
– Atmospheric depth 606g/cm2
– Wide field of view
– High duty cycle (>90%)
ASγ air shower array
ARGO
Experimental
Hall
Tibet Air Shower Array
Tibet-HD
Tibet-HD
Tibet array: ~250 x 250 m2
HD:
60 x 60m2
Tibet-III: ~150x150 m2
3,600m2 (in area)
Tibet-III
Live Time
Selected
Events
Mode
Energy
Resolution
(@3TeV)
Area
1997.2~1999.9
555.9 days
1.5×109
~3TeV
0.9o
3600m2
1999.11~2001.5
456.8 days
5.5×109
~3TeV
0.9o
22050m2
Operation
Time
TibetHD
Tibet-III
Method I -----Equal-zenith method

 i 1
10
*
N BG
Zenith
N OFFi
6.8°<zenith<40.0°
10
On-source
Off-source
North Pole
• Making use of the fact that events are uniformly distributed within
equal-zenith belt;
• 10 off-source windows (side band) are chosen to estimate BKG.
Method II----Global CR. Intensity fitting method
Zenith
N on
I on , N on
Equal ?

2
t , on

N on
I on 
N
N
i
 total 2  I i      t2,on
t , on
I off
2
off ,i
I off
i
2
I on

Equal !
Noff
I off , N off

 N on

I on
off ,i
2
I off
,i
,i

1

i

2


  1
 i

All sky survey based on an anisotropy
correction of relative CR intensity,
which is obtained by LSQ fitting for
the data in each of equal zenith ring
Large scale anisotropy (by method II)
DEC
I-1
～±0.1%
Tail-in and Loss-cone
Duldig, PASA,Vol18,No.1
RA.
Large scale anisotropy of diff. Data sample
• Anisotropy measurements agree with each other from using HD
detector or TibetIII detector, means small systematic effects.
Large scale anisotropy correction
σ=1.258
Before subtraction
σ=1.018
After subtraction
 Sky Map

0
0
(88.8,30.2)
List of sky cells with
clustered directions
(24)having statistic
significance larger
than 4.0σ.
Mrk421
Crab
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*
12
165.5
199.9
38.4
29.7
5.3
4.0
23
24
333.0
336.9
34.7
12.7
4.0
4.0
Discussion Hot point I ---evt. No.9 (88.8°, 30.2 °)
b=+5˚
b=+5˚
3.7σ
b=0˚
b=-5˚
4.5 σ
b=-5˚
b=+5˚
 SNR counterpart G179.0+2.6,
b=0˚
b=-5˚
b=0˚
5.6 σ
RA : 88.42 DEC :31.08
Size (/arc min): 70
Type: Shell
Hot Point II -- No.18(304.3 °, 36.7 °), No19(309.9 °,
39.6 °)
~0 σ
•
Amenomori,in Proc.27th ICRC,2315.
Observed 4.15 σ;
•
2.9 σ
28th
S.W. Cui and C.T. Yan, in Proc.
ICRC, 2315. Observed 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)
b=+5˚
b=0˚
b=-5˚
3.9 σ
4.5 σ
4.4 σ
4.2 σ
b=+5˚
b=+5˚
b=0˚
b=0˚
b=-5˚
b=-5˚
Up flux limit (by method I)
(30 degree of declination related to YBJ zenith direction)
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 with 5 σ level.
• No other significant point source is found, and an
upper-flux limit curve is given