arXiv subjects

W. L. Holzapfel

Publications and source records attributed to W. L. Holzapfel.

230 records · Page 13Linked to original sources

arXiv2001

The Sunyaev-Zel'dovich Effect: Results and Future Prospects

The Sunyaev-Zel'dovich effect (SZE) provides a powerful tool for cosmological studies. Through recent advances in instrumentation and observational techniques it is now possible to obtain high quality measurements of the effect toward galaxy clusters. The analysis of the SZE toward a few tens of clusters has already led to interesting constraints on the Hubble constant and the mass density of the universe. In the near future, instruments exploiting the redshift independence of the SZE will be used to conduct deep surveys for galaxy clusters providing detailed information on the growth of large scale structure, tests of cosmological models and tight constraints on the cosmological parameters that describe our universe. In this review we provide an overview of the SZE and its use for cosmological studies. We summarize the current state of observations and the constraints on cosmological parameters already obtained and we discuss the power of using the SZE for future deep cluster surveys.

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arXiv2001

First Intrinsic Anisotropy Observations with the Cosmic Background Imager

We present the first results of observations of the intrinsic anisotropy of the cosmic microwave background radiation with the Cosmic Background Imager from a site at 5080 m altitude in northern Chile. Our observations show a sharp decrease in C_l in the range l=400 - 1500. The broadband amplitudes we have measured are deltaT(band) = 58.7 (-6.3, +7.7) microK for l = 603 (-166, +180) and 29.7 (-4.2, +4.8) microK for l = 1190 (-224, +261), where these are half-power widths in l. Such a decrease in power at high l is one of the fundamental predictions of the standard cosmological model, and these are the first observations which cover a broad enough l range to show this decrease in a single experiment. The C_l we have measured enable us to place limits on the density parameter, Omega(tot) <= 0.4 or $Omega(tot) >= 0.7 (90% confidence).

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arXiv2000

Sunyaev-Zel'dovich Effect Derived Distances to the High Redshift Clusters MS 0451.6-0305 and CL 0016+16

We determine the distances to the z~0.55 galaxy clusters MS 0451.6-0305 and CL 0016+16 from a maximum likelihood joint fit to interferometric Sunyaev-Zel'dovich effect (SZE) and X-ray observations. We model the intracluster medium (ICM) using a spherical isothermal beta-model. We quantify the statistical and systematic uncertainties inherent to these direct distance measurements, and we determine constraints on the Hubble parameter for three different cosmologies. For an OmegaM = 0.3, OmegaL = 0.7 cosmology, these distances imply a Hubble constant of 63 ^{+12}_{- 9} ^{+21}_{-21} km/s/Mpc, where the uncertainties correspond to statistical followed by systematic at 68% confidence. The best fit Ho is 57 km/sec/Mpc for an open OmegaM = 0.3 universe and 52 km/s/Mpc for a flat Omega = 1 universe.

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arXiv1999

A Search for CMB Decrements Towards Distant Cluster Candidates PC1643+4631 and VLA1312+4237 at 28.5 GHz

Recently, Jones et al. (1997) used the Ryle telescope, operating at a frequency of 15 GHz, to detect a flux decrement in the direction of the quasar pair PC1643+461A,B. They interpreted this signal as the Sunyaev-Zel'dovich effect (SZE) produced by a distant cluster of galaxies. In the course of an effort to measure CMB anisotropies using the VLA at 8.4 GHz, Richards et al. (1997) detected a similar, but smaller, decrement which we refer to as VLA1312+4237. They also proposed that this signal might be explained as the SZE signal of a distant galaxy cluster. We report observations in the direction of these claimed sources with the Berkeley Illinois Maryland Association (BIMA) interferometer operating at 28.5 GHz. We find no evidence for SZE emission in the direction of either of the claimed sources. In the case of PC1643+4631, the BIMA data are inconsistent with the cluster emission model proposed by Jones et al. (1997) at greater than 99.99% confidence. Together with published x-ray and optical searches, these results make a compelling case against the existence of a massive cluster in the direction of PC1643+4631. Because of the different scales to which the VLA and BIMA instruments are sensitive, the BIMA observations are not as constraining for the VLA1312+4237 source. The BIMA data are inconsistent with the cluster model proposed by Richards et al. (1997) at approximately 80% confidence.

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arXiv1999

Limits on Arcminute Scale Cosmic Microwave Background Anisotropy with the BIMA Array

We have used the Berkeley-Illinois-Maryland-Association (BIMA) millimeter array outfitted with sensitive cm-wave receivers to search for Cosmic Microwave Background (CMB) anisotropies on arcminute scales. The interferometer was placed in a compact configuration which produces high brightness sensitivity, while providing discrimination against point sources. Operating at a frequency of 28.5 GHz, the FWHM primary beam of the instrument is 6.6 arcminutes. We have made sensitive images of seven fields, five of which where chosen specifically to have low IR dust contrast and be free of bright radio sources. Additional observations with the Owens Valley Radio Observatory (OVRO) millimeter array were used to assist in the location and removal of radio point sources. Applying a Bayesian analysis to the raw visibility data, we place limits on CMB anisotropy flat-band power Q_flat = 5.6 (+3.0 -5.6) uK and Q_flat < 14.1 uK at 68% and 95% confidence. The sensitivity of this experiment to flat band power peaks at a multipole of l = 5470, which corresponds to an angular scale of approximately 2 arcminutes. The most likely value of Q_flat is similar to the level of the expected secondary anisotropies.

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arXiv1999

A Sunyaev-Zel'dovich Effect Survey for High Redshift Clusters

Interferometric observations of the Sunyaev-Zel'dovich Effect (SZE) toward clusters of galaxies provide sensitive cosmological probes. We present results from 1 cm observations (at BIMA and OVRO) of a large, intermediate redshift cluster sample. In addition, we describe a proposed, higher sensitivity array which will enable us to survey large portions of the sky. Simulated observations indicate that we will be able to survey one square degree of sky per month to sufficient depth that we will detect all galaxy clusters more massive than 2x10^{14} h^{-1}_{50}M_\odot, regardless of their redshift. We describe the cluster yield and resulting cosmological constraints from such a survey.

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arXiv1999

Imaging the Sunyaev-Zel'dovich Effect

We report on results of interferometric imaging of the Sunyaev-Zel'dovich Effect (SZE) with the OVRO and BIMA mm-arrays. Using low-noise cm-wave receivers on the arrays, we have obtained high quality images for 27 distant galaxy clusters. We review the use of the SZE as a cosmological tool. Gas mass fractions derived from the SZE data are given for 18 of the clusters, as well as the implied constraint on the matter density of the universe, $Ω_M$. We find $Ω_M h_{100} \le 0.22 ^{+0.05}_{-0.03}$. A best guess for the matter density obtained by assuming a reasonable value for the Hubble constant and also by attempting to account for the baryons contained in the galaxies as well as those lost during the cluster formation process gives $Ω_M \sim 0.25$. We also give preliminary results for the Hubble constant. Lastly, the power for investigating the high redshift universe with a non-targeted high sensitivity SZE survey is discussed and an interferometric survey is proposed.

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arXiv1999

Anisotropy in the Cosmic Microwave Background at Degree Angular Scales: Python V Results

Observations of the microwave sky using the Python telescope in its fifth season of operation at the Amundsen-Scott South Pole Station in Antarctica are presented. The system consists of a 0.75 m off-axis telescope instrumented with a HEMT amplifier-based radiometer having continuum sensitivity from 37-45 GHz in two frequency bands. With a 0.91 deg x 1.02 deg beam the instrument fully sampled 598 deg^2 of sky, including fields measured during the previous four seasons of Python observations. Interpreting the observed fluctuations as anisotropy in the cosmic microwave background, we place constraints on the angular power spectrum of fluctuations in eight multipole bands up to l ~ 260. The observed spectrum is consistent with both the COBE experiment and previous Python results. There is no significant contamination from known foregrounds. The results show a discernible rise in the angular power spectrum from large (l ~ 40) to small (l ~ 200) angular scales. The shape of the observed power spectrum is not a simple linear rise but has a sharply increasing slope starting at l ~ 150.

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arXiv1997

The Sunyaev-Zel'dovich Infrared Experiment: A Millimeter-wave Receiver for Cluster Cosmology

Measurements of the Sunyaev-Zel'dovich (S-Z) effect towards distant clusters of galaxies can be used to determine the Hubble constant and the radial component of cluster peculiar velocities. Determination of the cluster peculiar velocity requires the separation of the two components of the S-Z effect, which are due to the thermal and bulk velocities of the intracluster plasma. The two components can be separated practically only at millimeter (mm) wavelengths. Measurements of the S-Z effect at mm wavelengths are subject to minimal astrophysical confusion and, therefore, provide an important test of results obtained at longer wavelengths. We describe the instrument used to make the first significant detections of the S-Z effect at millimeter wavelengths. This instrument employs new filter, detector, and readout technologies to produce sensitive measurements of differential sky brightness stable on long time scales. These advances allow drift scan observations which achieve high sensitivity while minimizing common sources of systematic error.

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arXiv1997

Measurement of the Hubble Constant from X-ray and 2.1 mm Observations of Abell 2163

We report 2.1 mm observations of the Sunyaev-Zel'dovich (S-Z) effect; these observations confirm our previous detection of a decrement in the Cosmic Microwave Background intensity towards the cluster Abell 2163. The S-Z data are analyzed using the relativistically correct expression for the Comptonization. We begin by assuming the intracluster (IC) gas to be isothermal at the emission weighted average temperature determined by a combined analysis of the ASCA and GINGA X-ray satellite observations. Combining the X-ray and S-Z measurements, we determine the Hubble constant to be H_0(q_0=0.5)= 60 +40/-23 km/s/Mpc, where the uncertainty is dominated by the systematic difference in the ASCA and GINGA determined IC gas temperatures. ASCA observations suggest the presence of a significant thermal gradient in the IC gas. We determine $H_0$ as a function of the assumed IC gas thermal structure. Using the ASCA determined thermal structure and keeping the emission weighted average temperature the same as in the isothermal case, we find H_0(q_0=0.5)= 78 +54/-28 km/s/Mpc. Including additional uncertainties due to cluster asphericity, peculiar velocity, IC gas clumping, and astrophysical confusion, we find H_0(q_0=0.5)= 78 +60/-40 km/s/Mpc.

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arXiv1997

Limits on the Peculiar Velocities of Two Distant Clusters Using the Kinematic Sunyaev-Zel'dovich Effect

We report millimeter-wavelength observations of the Sunyaev-Zel'dovich (S-Z) effect in two distant galaxy clusters. A relativistically correct analysis of the S-Z data is combined with the results of X-ray observations to determine the radial peculiar velocities v_r of the clusters. We observed Abell 2163 (z=.201) in three mm-wavelength bands centered at 2.1, 1.4, and 1.1 mm. We report a significant detection of the thermal component of the S-Z effect seen as both a decrement in the brightness of the CMB at 2.1 mm, and as an increment at 1.1 mm. Including uncertainties due to the calibration of the instrument, distribution and temperature of the IC gas, and astrophysical confusion, a simultaneous fit to the data in all three bands gives v_r=+490 +1370/-880 km/s at 68% confidence. We observed Abell 1689 (z=.181) in the 2.1 and 1.4 mm bands. Including the same detailed accounting of uncertainty, a simultaneous fit to the data in both bands gives v_r=+170 +815/-630 km/s. The limits on the peculiar velocities of A2163 and A1689 correspond to deviations from the uniform Hubble flow of <= 2-3%.

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arXiv1997

An Upper Limit to Arcminute Scale Anisotropy in the Cosmic Microwave Background Radiation at 142 GHz

We present limits to anisotropies in the cosmic microwave background radiation (CMB) at angular scales of a few arcminutes. The observations were made at a frequency of 142 GHz using a 6-element bolometer array (the Sunyaev-Zel'dovich Infrared Experiment) at the Caltech Submillimeter Observatory. Two patches of sky, each approximately 36'x4' and free of known sources, were observed for a total of 6-8 hours each, resulting in approximately 80 independent 1.7' full-width half-maximum pixels. Each pixel is observed with both a dual-beam and a triple-beam chop, with a sensitivity per pixel of 90-150 uK in each chop. These data have been analyzed using maximum likelihood techniques by assuming a gaussian autocorrelation function for the distribution of CMB fluctuations on the sky. We set an upper limit of Delta T/T <= 2.1 x 10^{-5} (95% confidence) for a coherence angle to the fluctuations of 1.1. These limits are comparable to the best limits obtained from centimeter-wavelength observations on similar angular scales but have the advantage that the contribution from known point sources is negligible at these frequencies. They are the most sensitive millimeter-wavelength limits for coherence angles <= 3'. The results are also considered in the context of secondary sources of anisotropy, specifically the Sunyaev-Zel'dovich effect from galaxy clusters.

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arXiv1997

Using SuZIE arcminute-scale CMB anisotropy data to probe open and flat-ΛCDM cosmogonies

We use arcminute-scale data from the Sunyaev-Zel'dovich Infrared Experiment to set limits on anisotropies in the cosmic microwave background radiation in open and spatially-flat-Lambda cold dark matter cosmogonies. There are no 2-sigma detections for the models tested. The upper limits obtained are consistent with the amplitude of anisotropy detected by the COBE/DMR experiment.

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arXiv1994

An Arcminute Resolution Search at 4.7CM^-1 for Point Sources in Msam and Max Fields

We have searched for mm-wave emission from compact objects in two fields, each approximately 1 square degree in size, taken from regions of the sky in which degree-scale structure in the Cosmic Background Radiation (CBR) has recently been reported. The observations were made at frequency of 4.7~cm^-1 and with an angular resolution of 1.7' using the Sunyaev-Zel'dovich Infrared Experiment (SuZIE) bolometer array at the Caltech Submillimeter Observatory (CSO). The first field was centered on 14.92hr +82deg (1994.0), one of two regions in which Cheng et al. (1994) identify the signature of an unresolved point source seen during 0.5 degree resolution observations made at 5.6~cm^-1 with the Medium Scale Anisotropy Measurement (MSAM) experiment. The second field was centered on 15.47hr +72.4deg (1994.0), part of the Gamma Ursae Minoris (GUM) region where several prominent features have been detected by Devlin et al. (1994) in 0.55 degree-resolution observations made at 3.5 and 6~cm^-1 with the Millimeter Anisotropy eXperiment (MAX). We find that there is no point source in either field that can account for the structure observed at 0.5 degree resolution, and that the structure must arise from objects with an angular size greater than 2'.

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