ASIAA NTU PHYS

J.H.P.Wu & AMiBA Team

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).

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 < 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.

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S-Z clusterby AMiBA

z RA DECX-ray temp.

[keV]β

Θc[arcsec]

Y2500(30 GHz)

[mJy]

Y2500(145 GHz)

[mJy]

HoursIntegrated

AMiBA(86-102 GHz)

[mJy]notes

A2142 0.089 15:58:20.5 27:13:36.7 8.68±0.12 1.0±0.3 221.4±8.4 - - 4.57 310 merger; lensing data

A2163 0.202 16:15:34.1 -6:07:26.0 12.2±1.0 0.674±0.010 87.5±2.5 143 533 5.96 330 merger with shock; high-temp. regions

A2261 0.224 17:22:27.6 32:07:37.2 8.82±0.35 0.516±0.013 15.7±1.1 40 440 8.22 140 lensing data

A2390 0.232 21:53:36.8 17:41:42.8 10.13±1.10 0.67 52.0 78 - 11.22 150 relaxed; lensing data

A1689 0.183 13:14:39.5 -1:20:28.1 9.66±0.20 0.609±0.005 26.6±0.7 57 460 9.38 190 relaxed; almost isothermal ; lensing data

A1995 0.322 14:52:50.4 58:02:48.0 8.59±0.70 0.770±0.80 38.9±5.0 25 4.37 130

AMiBA Spec

Dual-channel receiver MMIC; L and R Platform 6 m configurable; carbon fiber

Operation frequency 86-102 GHz Correlator analog (bandwidth 16 GHz)

Site Mauna Loa, Big Island, Hawaii (3400 m in elevation)

Mounting system Hexapod ( in polarization; in elevation)

7-element (2006-2008)

Antenna 60-cm Cassegrain; carbon fiber Synthesized resolution 6 arcmin

FOV 23 arcmin Observation type targeted

13-element (2009-)

Antenna 120-cm Cassegrain; carbon fiber Synthesized resolution 2 arcmin

FOV 11 arcmin Observation type targeted and survey

Based on the S-Z observations in 2007, we have successfully studied the following:1. Hubble parameter (with X-ray)2. Baryonic fraction (with lensing)3. SZ spectrum4. CMB foreground5. Detailed methods for calibration and data processing6. 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.)

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.

30 30 -90 CMB photons

CMB photons

S-Z effect CMB photons

0

( ) ( )T

g x yT

2

1, ( ) ( 4),

1

xT

e exe

kh ex g x x y n T dlkT e m c

k： Boltzmann constant (erg/K)h： Planck constantT： CMB temperaturey： Compton-y parameterσT ： Thomson cross section

c： speed of lightme ： electron massne ： electron number densityTe ： electron temperature

Inte

nsit

y

Frequency (ν)

AMiBA (86-102 GHz)

SZ effect

CMB photons

SZ effect:

S-Z clusters observed in 2007

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Science goals achieved in 2007

3

Observation Differencing test

P1P2