6 th IGPP meeting in Hawaii: March 21, 2007. Implication of the sidereal anisotropy of ~10 TeV (10 13 eV) cosmic ray intensity observed with the Tibet III air shower array.
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6th IGPP meeting in Hawaii: March 21, 2007
M. Amenomori, S. Ayabe, X. J. Bi, D. Chen, S. W. Cui, Danzengluobu, L. K. Ding, X. H. Ding, C. F. Feng, Zhaoyang Feng, Z. Y. Feng, X. Y. Gao, Q. X. Geng, H. W. Guo, H. H. He, M. He, K. Hibino, N. Hotta, Haibing Hu, H. B. Hu, J. Huang, Q. Huang, H. Y. Jia, F. Kajino, K. Kasahara, Y. Katayose, C. Kato, K. Kawata, Labaciren,
G. M. Le, A. F. Li, J. Y. Li, Y.Q. Lou, H. Lu, S. L. Lu, X. R. Meng, K. Mizutani, J. Mu, K. Munakata, A. Nagai,
H. Nanjo, M. Nishizawa, M. Ohnishi, I. Ohta, H. Onuma, T. Ouchi, S. Ozawa, J. R. Ren, T. Saito, T. Y. Saito,
M. Sakata, T. K. Sako, T. Sasaki, M. Shibata, A. Shiomi, T. Shirai, H. Sugimoto, M. Takita, Y. H. Tan,
N. Tateyama, S. Torii, H. Tsuchiya, S. Udo, B. Wang, H. Wang, X. Wang, Y. G. Wang, H. R. Wu, L. Xue,
Y. Yamamoto, C. T. Yan, X. C. Yang, S. Yasue, Z. H. Ye, G. C. Yu, A. F. Yuan, T. Yuda, H. M. Zhang, J. L. Zhang, N. J. Zhang, X. Y. Zhang, Y. Zhang, Yi Zhang, Zhaxisangzhu and X. X. Zhou
(Tibet AS collaboration)
85 people from 25 institutes in Japan and China
Cosmic ray observation with AS array
1ry g
Air shower array
Muon detector
Neutron monitor
533 counters of 0.5 m2 each placed on a 7.5mx7.5m square grid
Achieved…
Highest statistics &
Best angular resolution
in multiTeV region
Resolving the incident direction
d=30.1o
d=30.1o
AS flux varies for more than an order of magnitude with the zenith angle due to the different atmospheric depth.
●
Sidereal anisotropy on the spinning Earth
The zenith direction at Yanbajing is d=30.1o.
●
With the spin of Earth, the zenith direction travels along d=30.1o .
●
Fixed direction in the horizontal coordinate travels along d=const. for 360o of right ascension once every one sidereal day.
●
The average flux in each dband is subtracted.
2D sky map of CR intensity by Tibet AS
“Normalized” intensity map
(5°x5° pixels)
declination (º)
Galactic plane
Geographical equator
Nose direction
90° < 120° < 180°
Bidirectional + Unidirectional
right ascension (º)
~120°
(Amenomori et al., Science, 314, 2006)
Significance map
LIC (Local Interstellar Cloud)
T~7000K, nH~0.1/cc
Ionization rate~0.52
H
Redfield & Linsky, ApJ, 535, 2000
2 pc
l=90
He
Lallement’s Interstellar B plane
(Lallement et al., Science, 307, 2005)
l=180
GC
lB= 205~240
bB= 38~60
(or the opposite direction)
l=270
LIMC (Local Interstellar Magnetic Cloud) model
If cosmic ray density (n) is lower inside LIC than outside….
LIC
n High
Unidirectional flow
(Bxn)
n Low
G cloud
n
26 km/s
Bidirectional flow
Interstellar B
29 km/s
: Bidirectional
(DI/I)cal = a1cos1(a1,d1) : Unidirectional
+ a2+cos2 2(a2,d2) for 0 2/2
+ a2cos2 2(a2, d2) for /2 2
1, 2 : angles from reference axes
First choose orientations of reference axes…
a1,a2&d2 (or d1): (a2, d2) (a1, d1)
then a1, a2+&a2are given by linear LSM.
d.o.f. with 6 free parameters is large as…
90x360/(5x5)6=1,290
Result:
Unidirectional Bidirectional
a1=0.0016, a2+=0.0018, a2=0.0010
a1=27.5,d1=47.5, a2=97.4,d2=17.5
Bestfit intensity distribution
“Normalized” intensity
(average over dec.band is subtracted)
Original intensity
Unidirect.
+
Bidirect.
=
Sum
Cygnus region
Crab
Mrk421
observation
model
residual
(obs.model)/error
in twohemispheres
UGm in Japan V (35°N)
: LIMC model (Tibet AS)
Tibet AS
: Lallement’s B
UGm in Tasmania N (4°N)
Tibet AS
UGm in Tasmania V (36°S)
Bestfit B direction may be different when unbiased, by properly taking account of the data in southern hemisphere.
Tibet AS experiment cannot observe southern hemisphere.
UGm @0.5 TeV
Hall et al., JGR, 103, 1998 &104, 1999)
: Lallement’s B
+
+
: B in this model
(bidirectional)
0.0016
+0.0010

: heliotail (He)
b (°)
+0.0016
+
+
+0.0018
l (°)
Original intensity map (in galactic coordinate)
White lines show contour map of the distance to LIC boundary by Redfield & Linsky (2000).
Comparison with UG observations
Twohemisphere UG observations @~0.5 TeV
(5°x5° pixels)
(Hall et al., JGR, 103, 1998 &104, 1999)
(15°x15° pixels)
Largescale distribution of proton intensity (not ray)
Deep UG observations by Super Kamiokande @~10 TeV
Guillian et al., PRD, in press (2007)
“Normalized” intensity
Significance
4 TeV
6
No significant Edependence up to ~100 TeV
12
50
100
d=90o
d=30.1o
d=30.1o
恒星時日周変動
系統誤差 0.01%を実現
0 6 12 18 24
Local sidereal time (hour)
銀河異方性と恒星時日周変動
赤緯依存性を観測できない。
（自転軸に平行な流れは検出不可）
Nagashima, Fuｊimoto & Jacklyn (1998)
Losscone
Losscone
TailIn
TailIn
Espectra of SDV amplitude
（Before Tibet III）
Amenomori et al. (ApJL, 626, 2005)