18 research outputs found
AMiBA: Cluster Sunyaev-Zel’dovich Effect Observations with the Expanded 13-element Array
The Yuan-Tseh Lee Array for Microwave Background Anisotropy (AMiBA) is a co-planar interferometer array operating at a wavelength of 3 mm to measure the Sunyaev-Zel’dovich effect (SZE) of galaxy clusters at arcminute scales. The first phase of operation—with a compact 7-element array with 0.6 m antennas (AMiBA-7)—observed six clusters at angular scales from 5\\prime to 23\\prime . Here, we describe the expansion of AMiBA to a 13-element array with 1.2 m antennas (AMiBA-13), its subsequent commissioning, and cluster SZE observing program. The most noticeable changes compared to AMiBA-7 are (1) array re-configuration with baselines ranging from 1.4 m to 4.8 m, allowing us to sample structures between 2\\prime and 10\\prime , (2) 13 new lightweight carbon-fiber-reinforced plastic (CFRP) 1.2 m reflectors, and (3) additional correlators and six new receivers. Since the reflectors are co-mounted on and distributed over the entire six-meter CFRP platform, a refined hexapod pointing error model and phase error correction scheme have been developed for AMiBA-13. These effects—entirely negligible for the earlier central close-packed AMiBA-7 configuration—can lead to additional geometrical delays during observations. Our correction scheme recovers at least 80 ± 5% of the point-source fluxes. We, therefore, apply an upward correcting factor of 1.25 to our visibilities to correct for phase decoherence, and a ±5% systematic uncertainty is added in quadrature with our statistical errors. We demonstrate the absence of further systematics with a noise level consistent with zero in stacked uv-visibilities. From the AMiBA-13 SZE observing program, we present here maps of a subset of 12 clusters with signal-to-noise ratios above five. We demonstrate combining AMiBA-7 with AMiBA-13 observations on Abell 1689, by jointly fitting their data to a generalized Navarro-Frenk-White model. Our cylindrically integrated Compton-y values for five radii are consistent with results from the Berkeley-Illinois-Maryland Array, the Owens Valley Radio Observatory, the Sunyaev-Zel’dovich Array, and the Planck Observatory. We also report the first targeted SZE detection toward the optically selected cluster RCS J1447+0828, and we demonstrate the ability of AMiBA SZE data to serve as a proxy for the total cluster mass. Finally, we show that our AMiBA-SZE derived cluster masses are consistent with recent lensing mass measurements in the literature
AMiBA: scaling relations between the integrated Compton-y and X-ray derived temperature, mass, and luminosity
We investigate the scaling relations between the X-ray and the thermal
Sunyaev-Zel'dovich Effect (SZE) properties of clusters of galaxies, using data
taken during 2007 by the Y.T. Lee Array for Microwave Background Anisotropy
(AMiBA) at 94 GHz for the six clusters A1689, A1995, A2142, A2163, A2261, and
A2390. The scaling relations relate the integrated Compton-y parameter Y_{2500}
to the X-ray derived gas temperature T_{e}, total mass M_{2500}, and bolometric
luminosity L_X within r_{2500}. Our results for the power-law index and
normalization are both consistent with the self-similar model and other studies
in the literature except for the Y_{2500}-L_X relation, for which a physical
explanation is given though further investigation may be still needed. Our
results not only provide confidence for the AMiBA project but also support our
understanding of galaxy clusters.Comment: Accepted by ApJ; 8 pages, 3 figures, 5 table
Platform Deformation Phase Correction for the AMiBA-13 Coplanar Interferometer
[[abstract]]We present a new way to solve the platform deformation problem of coplanar interferometers. The platform of a coplanar interferometer can be deformed due to driving forces and gravity. A deformed platform will induce extra components into the geometric delay of each baseline and change the phases of observed visibilities. The reconstructed images will also be diluted due to the errors of the phases. The platform deformations of The Yuan-Tseh Lee Array for Microwave Background Anisotropy (AMiBA) were modeled based on photogrammetry data with about 20 mount pointing positions. We then used the differential optical pointing error between two optical telescopes to fit the model parameters in the entire horizontal coordinate space. With the platform deformation model, we can predict the errors of the geometric phase delays due to platform deformation with a given azimuth and elevation of the targets and calibrators. After correcting the phases of the radio point sources in the AMiBA interferometric data, we recover 50%-70% flux loss due to phase errors. This allows us to restore more than 90% of a source flux. The method outlined in this work is not only applicable to the correction of deformation for other coplanar telescopes but also to single-dish telescopes with deformation problems. This work also forms the basis of the upcoming science results of AMiBA-13.[[notice]]補正完畢[[journaltype]]國外[[incitationindex]]SCI[[ispeerreviewed]]Y[[booktype]]電子版[[booktype]]紙本[[countrycodes]]US
AMiBA: Sunyaev-Zel'Dovich Effect-derived Properties and Scaling Relations of Massive Galaxy Clusters
99學年度劉國欽研究獎助論文
100學年度劉國欽升等參考著作[[abstract]]The Sunyaev-Zel'dovich Effect (SZE) has been observed toward six massive galaxy clusters, at redshifts 0.091 ≤ z ≤ 0.322 in the 86-102 GHz band with the Y. T. Lee Array for Microwave Background Anisotropy (AMiBA). We modify an iterative method, based on the isothermal β models, to derive the electron temperature T e, total mass M t, gas mass M g, and integrated Compton Y within r 2500, from the AMiBA SZE data. Non-isothermal universal temperature profile (UTP) β models are also considered in this paper. These results are in good agreement with those deduced from other observations. We also investigate the embedded scaling relations, due to the assumptions that have been made in the method we adopted, between these purely SZE-deduced T e, M t, M g, and Y. Our results suggest that cluster properties may be measurable with SZE observations alone. However, the assumptions built into the pure-SZE method bias the results of scaling relation estimations and need further study.[[journaltype]]國外[[incitationindex]]SCI[[booktype]]紙本[[booktype]]電子版[[countrycodes]]US
Constraining Intra-cluster Gas Models with AMiBA13
Clusters of galaxies have been used extensively to determine cosmological
parameters. A major difficulty in making best use of Sunyaev-Zel'dovich (SZ)
and X-ray observations of clusters for cosmology is that using X-ray
observations it is difficult to measure the temperature distribution and
therefore determine the density distribution in individual clusters of galaxies
out to the virial radius. Observations with the new generation of SZ
instruments are a promising alternative approach. We use clusters of galaxies
drawn from high-resolution adaptive mesh refinement (AMR) cosmological
simulations to study how well we should be able to constrain the large-scale
distribution of the intra-cluster gas (ICG) in individual massive relaxed
clusters using AMiBA in its configuration with 13 1.2-m diameter dishes
(AMiBA13) along with X-ray observations. We show that non-isothermal beta
models provide a good description of the ICG in our simulated relaxed clusters.
We use simulated X-ray observations to estimate the quality of constraints on
the distribution of gas density, and simulated SZ visibilities (AMiBA13
observations) for constraints on the large-scale temperature distribution of
the ICG. We find that AMiBA13 visibilities should constrain the scale radius of
the temperature distribution to about 50% accuracy. We conclude that the
upgraded AMiBA, AMiBA13, should be a powerful instrument to constrain the
large-scale distribution of the ICG.Comment: Accepted for publication in The Astrophysical Journal, 12 pages, 9
figure
Tests of AMiBA Data Integrity
We describe methods used to validate data from the Y.T. Lee Array for
Microwave Background Anisotropy (AMiBA), an interferometric array designed to
measure the Sunyaev-Zel'dovich effect and the anisotropy of the Cosmic
Microwave Background (CMB). We perform several statistical tests on data from
pointed galaxy cluster observations taken in 2007 and noise data from long-term
blank sky observations and measurements with the feeds covered by the
absorbers. We apply power spectrum analysis, cross power spectrum analysis
among different outputs with different time lags in our analog correlator, and
sample variance law tests to noise data. We find that (1) there is no time
variation of electronic offsets on the time scale of our two-patch observations
(~10 minutes); (2) noise is correlated by less than 10% between different lags;
and (3) the variance of noise scales with the inverse of time. To test the
Gaussianity of the data, we apply Kolmogorov-Smirnov (K-S) tests to cluster
data, and find that a 5% significance level efficiently detects data sets with
known hardware problems without rejecting an excess of acceptable data. We also
calculate third- and fourth-order moments and cumulants for the noise residual
visibilities and find that about 95% of our data are within the 99% confidence
regions of Gaussianity.Comment: 15 pages, 5 figures, accepted for publication in Ap
AMiBA: System Performance
The Y.T. Lee Array for Microwave Background Anisotropy (AMiBA) started
scientific operation in early 2007. This work describes the optimization of the
system performance for the measurements of the Sunyaev-Zel'dovich effect for
six massive galaxy clusters at redshifts . We achieved a point
source sensitivity of mJy with the seven 0.6m dishes in 1 hour of
on-source integration in 2-patch differencing observations. We measured and
compensated for the delays between the antennas of our platform-mounted
interferometer. Beam switching was used to cancel instrumental instabilities
and ground pick up. Total power and phase stability were good on time scales of
hours, and the system was shown to integrate down on equivalent timescales of
300 hours per baseline/correlation, or about 10 hours for the entire array.
While the broadband correlator leads to good sensitivity, the small number of
lags in the correlator resulted in poorly measured bandpass response. We
corrected for this by using external calibrators (Jupiter and Saturn). Using
Jupiter as the flux standard, we measured the disk brightness temperature of
Saturn to be K.Comment: 9 pages, 7 figures, 1 table, accepted for publication in Ap
Contamination of the Central Sunyaev--Zel'dovich Decrements in AMiBA Galaxy Cluster Observations
We investigate the contamination of the Sunyaev--Zel'dovich (SZ) effect for
six galaxy clusters, A1689, A1995, A2142, A2163, A2261, and A2390, observed by
the Y. T. Lee Array for Microwave Background Anisotropy during 2007. With the
range of baselines used, we find that the largest effect (of order 13%-50% of
the central SZ flux density) comes from primary anisotropies in the cosmic
microwave background and exceeds the thermal noise in all six cases.
Contamination from discrete radio sources is estimated to be at a level of
(3%-60%) of the central SZ flux density. We use the statistics of these
contaminating sources to estimate and correct the errors in the measured SZ
effects of these clusters.Comment: 22 pages, 2 figure
Mass and Hot Baryons in Massive Galaxy Clusters from Subaru Weak Lensing and AMiBA SZE Observations
We present a multiwavelength analysis of a sample of four hot (T_X>8keV)
X-ray galaxy clusters (A1689, A2261, A2142, and A2390) using joint AMiBA
Sunyaev-Zel'dovich effect (SZE) and Subaru weak lensing observations, combined
with published X-ray temperatures, to examine the distribution of mass and the
intracluster medium (ICM) in massive cluster environments. Our observations
show that A2261 is very similar to A1689 in terms of lensing properties. Many
tangential arcs are visible around A2261, with an effective Einstein radius
\sim 40 arcsec (at z \sim 1.5), which when combined with our weak lensing
measurements implies a mass profile well fitted by an NFW model with a high
concentration c_{vir} \sim 10, similar to A1689 and to other massive clusters.
The cluster A2142 shows complex mass substructure, and displays a shallower
profile (c_{vir} \sim 5), consistent with detailed X-ray observations which
imply recent interaction. The AMiBA map of A2142 exhibits an SZE feature
associated with mass substructure lying ahead of the sharp north-west edge of
the X-ray core suggesting a pressure increase in the ICM. For A2390 we obtain
highly elliptical mass and ICM distributions at all radii, consistent with
other X-ray and strong lensing work. Our cluster gas fraction measurements,
free from the hydrostatic equilibrium assumption, are overall in good agreement
with published X-ray and SZE observations, with the sample-averaged gas
fraction of = 0.133 \pm 0.027, for our sample = (1.2 \pm
0.1) \times 10^{15} M_{sun} h^{-1}. When compared to the cosmic baryon fraction
f_b = \Omega_b/\Omega_m constrained by the WMAP 5-year data, this indicates
/f_b = 0.78 \pm 0.16, i.e., (22 \pm 16)% of the baryons are missing
from the hot phase of clusters.Comment: accepted for publication in ApJ; high resolution figures available at
http://www.asiaa.sinica.edu.tw/~keiichi/upfiles/AMiBA7/ms_highreso.pd
The Yuan-Tseh Lee Array for Microwave Background Anisotropy
The Yuan-Tseh Lee Array for Microwave Background Anisotropy (AMiBA) is the
first interferometer dedicated to studying the cosmic microwave background
(CMB) radiation at 3mm wavelength. The choice of 3mm was made to minimize the
contributions from foreground synchrotron radiation and Galactic dust emission.
The initial configuration of seven 0.6m telescopes mounted on a 6-m hexapod
platform was dedicated in October 2006 on Mauna Loa, Hawaii. Scientific
operations began with the detection of a number of clusters of galaxies via the
thermal Sunyaev-Zel'dovich effect. We compare our data with Subaru weak lensing
data in order to study the structure of dark matter. We also compare our data
with X-ray data in order to derive the Hubble constant.Comment: accepted for publication in ApJ (13 pages, 7 figures); a version with
high resolution figures available at
http://www.asiaa.sinica.edu.tw/~keiichi/upfiles/AMiBA7/pho_highreso.pd