X-ray Spectroscopy of Clusters of Galaxies

Clusters of galaxies are the most massive objects in the Universe and precise knowledge of their mass structure is important to understand the history of structure formation and constrain still unknown types of dark contents of the Universe. X-ray spectroscopy of galaxy clusters provides rich information about the physical state of hot intracluster gas and the underlying potential structure. In this paper, starting from the basic description of clusters under equilibrium conditions, we review properties of clusters revealed primarily through X-ray observations considering their thermal and dynamical evolutions. The future prospects of cluster studies using upcoming X-ray missions are also mentioned.Comment: Review article for "Frontiers in Astrophysics" - a special issue dedicated to the IAU XXVIIIth General Assembly. 22 pages, 11 figure

Statistical anisotropy in CMB spectral distortions

Measurements of the cosmic microwave background (CMB) spectral $y$-distortion anisotropy offer a test for the statistical isotropy of the primordial density perturbations on $0.01\lesssim k{\rm Mpc}\lesssim 1$. We compute the 1-point ensemble averages of the $y$-distortion anisotropies which vanish for the statistically isotropic perturbations. For the quadrupole statistical anisotropy, we find $4\pi\langle y_{2m}\rangle=-6.8A_2\times 10^{-9}Y_{2m}(\mathbf d )$ with the quadruple Legendre coefficient of the anisotropic powerspectrum $A_2$ and the $\ell=2$ spherical harmonics $Y_{2m}(\mathbf d )$ for the preferred direction $\mathbf d$. Also, we discuss the cosmic variance of the $y$-distortion anisotropy in the statistically anisotropic Universe.Comment: 5 pages, 4 figures, published versio

The Impact of Suzaku Measurements on Astroparticle Physics

Results from the Suzaku X-ray broad-band observations of clusters of galaxies are summarized. Aiming at understanding the physics of gas heating/particle acceleration and the cluster dynamical evolution, we search for non-thermal hard X-ray emission from merging clusters, particularly A2163 and the Bullet Cluster, based on the Suzaku and XMM-Newton/Chandra joint analyses. The observed hard X-ray emission is well represented by single- or multi-temperature thermal models, including super-hot (kT~20 keV) gas. However, no significant non-thermal hard X-ray emission has been detected. Together with the presently available literature, the hard X-ray properties have been studied for about 10 clusters with Suzaku. The present status on Suzaku measurements of non-thermal X-ray emission and the cluster magnetic field are summarized and compared with those from the RXTE, BeppoSAX, and Swift satellites. The future prospects are briefly mentioned.Comment: To appear in Acta Polytechnica. Invited talk at the Vulcano Workshop 2012 "Frontier Objects in Astrophysics and Particle Physics". 6 pages, 3 figures. Typo correcte