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Register a new userSunyaev-Zeldovich Effect as a Cosmological Probe
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Authors
Asantha R. Cooray
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We review recent results of Sunyaev-Zeldovich effect (SZE) observations toward galaxy clusters. Using cm-wave receivers mounted on the OVRO and BIMA mm-wave arrays we have obtained high signal to noise images of the effect for more than 20 clusters. We present current estimates of the Hubble constant and cosmological parameters and discuss the potential of conducting statistical studies with large SZE cluster samples.
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We explore the potential of the kinetic Sunyaev-Zeldovich (kSZ) effect as the cornerstone of a future observational probe for halo spin bias, the secondary dependence of halo clustering on halo spin at fixed halo mass. Using the IllustrisTNG magneto-hydrodynamical cosmological simulation, we measure both the kSZ and the thermal SZ (tSZ) effects produced by the baryonic content of more than 50,000 haloes within the halo mass range $11 < log_{10} ({rm M_{vir}}/ h^{-1} {rm M_{odot}}) lesssim 14.5$. First, we confirm that the magnitude of both effects depends strongly on the total gas and virial mass of the haloes, and that the integrated kSZ signal displays a significant correlation with the angular momentum of the intra-halo gas, particularly for massive haloes. Second, we show that both the integrated kSZ signal and the ratio of the integrated kSZ and tSZ signals trace total halo spin, even though significant scatter exists. Finally, we demonstrate that, in the absence of observational and instrumental uncertainties, these SZ-related statistics can be used to recover most of the underlying IllustrisTNG halo spin bias signal. Our analysis represents the first attempt to develop a future observational probe for halo spin bias, bringing forward alternative routes for measuring the secondary bias effects.
X-ray observations of an entropy floor in nearby groups and clusters of galaxies offer evidence that important non-gravitational processes, such as radiative cooling and/or preheating, have strongly influenced the evolution of the intracluster medium (ICM). We examine how the presence of an entropy floor modifies the thermal Sunyaev-Zeldovich (SZ) effect. A detailed analysis of scaling relations between X-ray and SZ effect observables and also between the two primary SZ effect observables is presented. We find that relationships between the central Compton parameter and the temperature or mass of a cluster are extremely sensitive to the presence of an entropy floor. The same is true for correlations between the integrated Compton parameter and the X-ray luminosity or the central Compton parameter. In fact, if the entropy floor is as high as inferred in recent analyses of X-ray data, a comparison of these correlations with both current and future SZ effect observations should show a clear signature of this excess entropy. Moreover, because the SZ effect is redshift-independent, the relations can potentially be used to track the evolution of the cluster gas and possibly discriminate between the possible sources of the excess entropy. To facilitate comparisons with observations, we provide analytic fits to these scaling relations.
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S. M. Molnar (Laboratory for High Energy Astrophysics
, n Goddard/Department of Physics
, Astronomy
2002
We discuss how the space of possible cosmological parameters is constrained by the angular diameter distance function, D_A(z), as measured using the SZ/X-ray method which combines Sunyaev-Zeldovich (SZ) effect and X-ray brightness data for clusters of galaxies. New X-ray satellites, and ground-based interferometers dedicated to SZ observations, should soon lead to D_A(z) measurements limited by systematic rather than random error. We analyze the systematic and random error budgets to make a realistic estimate of the accuracy achievable in the determination of (Omega_m,Lambda,h), the density parameters of matter and cosmological constant, and the dimensionless Hubble constant, using D_A(z) derived from the SZ/X-ray method, and the position of the first ``Doppler peak in the cosmic microwave background fluctuations. We briefly study the effect of systematic errors. We find that Omega_m, Lambda, and w are affected, but h is not by systematic errors which grow with redshift. With as few as 70 clusters, each providing a measurement of D_A(z) with a 7% random and 5% systematic error, Omega_m can be constrained to +/-0.2, Lambda to +/-0.2, and h to +/-0.11 (all at 3 sigma). We also estimate constraints for the alternative three-parameter set (Omega_m,w,h), where w is the equation of state parameter. The measurement of D_A(z) provides constraints complementary to those from the number density of clusters in redshift space. A sample of 70 clusters (D_A measured with the same accuracy as before) combined with cluster evolution results (or a known matter density), can constrain w within +/-0.45 (at 3 sigma). Studies of X-ray and SZ properties of clusters of galaxies promise an independent and powerful test for cosmological parameters.
We discuss how future cluster surveys can constrain cosmological parameters with particular reference to the properties of the dark energy component responsible for the observed acceleration of the universe by probing the evolution of the surface density of clusters as a function of redshift. We explain how the abundance of clusters selected using their Sunyaev-Zeldovich effect can be computed as a function of the observed flux and redshift taking into account observational effects due to a finite beam-size. By constructing an idealized set of simulated observations for a fiducial model, we forecast the likely constraints that might be possible for a variety of proposed surveys which are assumed to be flux limited. We find that Sunyaev-Zeldovich cluster surveys can provide vital complementary information to those expected from surveys for supernovae. We analyse the impact of statistical and systematic uncertainties and find that they only slightly limit our ability to constrain the equation of state of the dark energy component.
The South Pole Telescope (SPT) is conducting a Sunyaev-Zeldovich (SZ) effect survey over large areas of the southern sky, searching for massive galaxy clusters to high redshift. In this preliminary study, we focus on a 40 square-degree area targeted by the Blanco Cosmology Survey (BCS), which is centered roughly at right ascension 5h30m, declination -53 degrees. Over two seasons of observations, this entire region has been mapped by the SPT at 95 GHz, 150 GHz, and 225 GHz. We report the four most significant SPT detections of SZ clusters in this field, three of which were previously unknown and, therefore, represent the first galaxy clusters discovered with an SZ survey. The SZ clusters are detected as decrements with greater than 5-sigma significance in the high-sensitivity 150 GHz SPT map. The SZ spectrum of these sources is confirmed by detections of decrements at the corresponding locations in the 95 GHz SPT map and non-detections at those locations in the 225 GHz SPT map. Multiband optical images from the BCS survey demonstrate significant concentrations of similarly colored galaxies at the positions of the SZ detections. Photometric redshift estimates from the BCS data indicate that two of the clusters lie at moderate redshift (z ~ 0.4) and two at high redshift (z >~ 0.8). One of the SZ detections was previously identified as a galaxy cluster using X-ray data from the ROSAT All-Sky Survey (RASS). Potential RASS counterparts (not previously identified as clusters) are also found for two of the new discoveries. These first four galaxy clusters are the most significant SZ detections from a subset of the ongoing SPT survey. As such, they serve as a demonstration that SZ surveys, and the SPT in particular, can be an effective means for finding galaxy clusters.
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