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Register a new userLow-resolution spectroscopy of the Sunyaev-Zeldovich effect and estimates of cluster parameters
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The Sunyaev-Zeldovich (SZ) effect is a powerful tool for studying clusters of galaxies and cosmology. Large mm-wave telescopes are now routinely detecting and mapping the SZ effect in a number of clusters, measure their comptonisation parameter and use them as probes of the large-scale structure and evolution of the universe. We show that estimates of the physical parameters of clusters (optical depth, plasma temperature, peculiar velocity, non-thermal components etc.) obtained from ground-based multi-band SZ photometry can be significantly biased, owing to the reduced frequency coverage, to the degeneracy between the parameters and to the presence of a number of independent components larger than the number of frequencies measured. We demonstrate that low-resolution spectroscopic measurements of the SZ effect that also cover frequencies $> 270$ GHz are effective in removing the degeneracy. We used accurate simulations of observations with lines-of-sight through clusters of galaxies with different experimental configurations (4-band photometers, 6-band photometer, multi-range differential spectrometer, full coverage spectrometers) and different intracluster plasma stratifications. We find that measurements carried out with ground-based few-band photometers are biased towards high electron temperatures and low optical depths, and require coverage of high frequency and/or independent complementary observations to produce unbiased information; a differential spectrometer that covers 4 bands with a resolution of $sim 6 GHz$ eliminates most if not all bias; full-range differential spectrometers are the ultimate resource that allows a full recovery of all parameters.
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Studying galaxy clusters through their Sunyaev-Zeldovich (SZ) imprint on the Cosmic Microwave Background has many important advantages. The total SZ signal is an accurate and precise tracer of the total pressure in the intra-cluster medium and of cluster mass, the key observable for using clusters as cosmological probes. Band 5 observations with SKA-MID towards cluster surveys from the next generation of X-ray telescopes such as e-ROSITA and from Euclid will provide the robust mass estimates required to exploit these samples. This will be especially important for high redshift systems, arising from the SZs unique independence to redshift. In addition, galaxy clusters are very interesting astrophysical systems in their own right, and the SKAs excellent surface brightness sensitivity down to small angular scales will allow us to explore the detailed gas physics of the intra-cluster medium.
The galaxy cluster Zwicky 3146 is a sloshing cool core cluster at $z=0.291$ that in X-ray imaging does not appear to exhibit significant pressure substructure in the intracluster medium (ICM). The published $M_{500}$ values range between $3.88^{+0.62}_{-0.58}$ to $22.50 pm 7.58 times 10^{14}$ M$_{odot}$, where ICM-based estimates with reported errors $<20$% suggest that we should expect to find a mass between $6.53^{+0.44}_{-0.44} times 10^{14}$ M$_{odot}$ (from Planck, with an $8.4sigma$ detection) and $8.52^{+1.77}_{-1.47} times 10^{14}$ M$_{odot}$ (from ACT, with a $14sigma$ detection). This broad range of masses is suggestive that there is ample room for improvement for all methods. Here, we investigate the ability to estimate the mass of Zwicky 3146 via the Sunyaev-Zeldovich (SZ) effect with data taken at 90 GHz by MUSTANG-2 to a noise level better than $15 mu$K at the center, and a cluster detection of $104sigma$. We derive a pressure profile from our SZ data which is in excellent agreement with that derived from X-ray data. From our SZ-derived pressure profiles, we infer $M_{500}$ and $M_{2500}$ via three methods -- $Y$-$M$ scaling relations, the virial theorem, and hydrostatic equilibrium -- where we employ X-ray constraints from emph{XMM-Newton} on the electron density profile when assuming hydrostatic equilibrium. Depending on the model and estimation method, our $M_{500}$ estimates range from $6.23 pm 0.59$ to $10.6 pm 0.95 times 10^{14}$ M$_{odot}$, where our estimate from hydrostatic equilibrium, is $8.29^{+1.93}_{-1.24}$ ($pm 19.1$% stat) ${}^{+0.74}_{-0.68}$ ($pm 8.6$% sys, calibration) $times 10^{14}$ M$_{odot}$. Our fiducial mass, derived from a $Y$-$M$ relation is $8.16^{+0.44}_{-0.54}$ ($pm 5.5$% stat) ${}^{+0.46}_{-0.43}$ ($pm 5.5$% sys, $Y$-$M$) ${}^{+0.59}_{-0.55}$ ($pm 7.0$% sys, cal.) $times 10^{14}$ M$_{odot}$.
Using high-resolution microwave sky maps made by the Atacama Cosmology Telescope, we for the first time present strong evidence for motions of galaxy clusters and groups via microwave background temperature distortions due to the kinematic Sunyaev-Zeldovich effect. Galaxy clusters are identified by their constituent luminous galaxies observed by the Baryon Oscillation Spectroscopic Survey, part of the Sloan Digital Sky Survey III. We measure the mean pairwise momentum of clusters, with a probability of the signal being due to random errors of 0.002, and the signal is consistent with the growth of cosmic structure in the standard model of cosmology.
We present initial results from our ongoing program to image the Sunyaev-Zeldovich (SZ) effect in galaxy clusters at 143 GHz using Bolocam; five clusters and one blank field are described in this manuscript. The images have a resolution of 58 arcsec and a radius of 6-7 arcmin, which is approximately r500 - 2r500 for these clusters. The beam-smoothed RMS is ~10 uK_CMB in these images; with this sensitivity we are able to detect SZ signal to beyond r500 in binned radial profiles. We have fit our images to beta and Nagai models, fixing spherical symmetry or allowing for ellipticity in the plane of the sky, and we find that the best-fit parameter values are in general consistent with those obtained from other X-ray and SZ data. Our data show no clear preference for the Nagai model or the beta model due to the limited spatial dynamic range of our images. However, our data show a definitive preference for elliptical models over spherical models. The weighted mean ellipticity of the five clusters is 0.27 +- 0.03, consistent with results from X-ray data. Additionally, we obtain model-independent estimates of Y500, the integrated SZ y-parameter over the cluster face to a radius of r500, with systematics-dominated uncertainties of ~10%. Our Y500 values, which are free from the biases associated with model-derived Y500 values, scale with cluster mass in a way that is consistent with both self-similar predictions and expectations of a 10% intrinsic scatter.
We consider the Stokes parameters frequency spectral distortions arising due to Compton scattering of the anisotropic cosmic microwave background (CMB) radiation, the Sunyaev-Zel dovich effect (SZ), towards clusters of galaxies. We single out a very special type of such distortions and find simple analytical formulas for them. We show that this kind of distortion has a very distinctive spectral shape and can be separated from other kinds of contaminants. We demonstrate that this effect gives us an opportunity for an independent estimation of the low-multipole angular CMB anisotropies, such as the dipole, the quadrupole, and the octupole. We also show that, using distorted signals from nearby and distant clusters, one can distinguish between the Sachs-Wolfe and the integrated Sachs-Wolfe effects. The detection of such distortions can be feasible with high-angular resolution and high-sensitivity space missions, such as the upcoming Millimetron Space Observatory experiment.
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