AMiBA: FirstYear Results

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AMiBA First-Year Results
for Sunyaev-Zel'dovich Effect
J.H.P.Wu AMiBA Team
The Y.T. Lee Array for Microwave Background
Anisotropy (previously known as Array for
Microwave Background Anisotropy, AMiBA) is an
interferometric experiment designed to study
cosmology via the measurement of Cosmic Microwave
Background (CMB). It is located at Mauna Loa, Big
Island, Hawaii. In 2007, 6 galaxy clusters (z lt
0.33) were observed through the
Sunyaev-Zel'dovich effect. These are the first
science results of AMiBA from which we have
studied not only the cluster physics but also the
cosmic origin.
AMiBA (86-102 GHz)
CMB photons
SZ effect
S-Z effect
CMB photons
Intensity
CMB photons
CMB photons
Frequency (?)
SZ effect
kBoltzmann constant (erg/K) hPlanck
constant TCMB temperature yCompton-y
parameter sTThomson cross section
cspeed of light meelectron mass neelectron
number density Teelectron temperature
Differencing test
Observation
To remove the ground pickup and electronic DC
component in the data, we tracked the source-
(P1) and tail- (P2) patches along the same (Az,
El). A differencing (P1-P2) in the analysis
successfully extracted out the cluster signal
(see below). Platform was also rotated to obtain
better u-v coverage (right).
Two complementary data subsets were processed
separately (see below, left and middle), and
their differencing (right) shows no essential
residual signal. This provides strong evidence
that the observed signal is indeed from a cluster
(A2142 in this case) rather than from our
instrument.
P1
P2
S-Z clusters observed in 2007
Science goals achieved in 2007

• Based on the S-Z observations in 2007, we have
  successfully studied the following
• Hubble parameter (with X-ray)
• Baryonic fraction (with lensing)
• SZ spectrum
• CMB foreground
• Detailed methods for calibration and data
  processing
• Test of data integrity such as non-Gaussianity
  test
• Below is the expected performance in measuring
  the CMB power spectrum, which is to be observed
  in 2008.

Calibrated with Jupiter, Saturn, and Mars, the
figure below shows the constructed images of the
observed S-Z clusters. The evident temperature
decrement at the centers is a theoretically
expected feature for S-Z signals at around 94 GHz
(see illustration at the top). These data have
been further used to investigate the cluster
physics and the origin of the Universe. (The
circles indicate the resolution.)
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