Time of primordial Be-7 conversion into Li-7, energy release and doublet of narrow cosmological neutrino lines

One of the important light elements created during the big bang nucleosynthesis is Be-7 which then decays to Li-7 by electron capture when recombination becomes effective but well before the Saha equilibrium recombination is reached. This means that Be-7 should wait until its recombination epoch even though the half-life of the hydrogenic beryllium atom is only 106.4 days. We calculate when the conversion from primordial Be-7 to Li-7 occurs taking into account the population of the hyperfine structure sublevels and solving the kinetic equations for recombination, photoionization and conversion rate. We also calculate the energies and the spectrum of narrow neutrino doublet lines resulting from Be-7 decay.Comment: Minor typos correcte

Large scale motions in superclusters: their imprint in the CMB

We identify high density regions of supercluster size in high resolution N-body simulations of a representative volume of three Cold Dark Matter Universes. By assuming that (1) the density and peculiar velocities of baryons trace those of the dark matter, and (2) the temperature of plasma is proportional to the velocity dispersion of the dark matter particles in regions where the crossing times is smaller than the supercluster free-fall time, we investigate how thermal motions of electrons in the intra-cluster medium and peculiar velocity of clusters can affect the secondary anisotropies in the cosmic microwave background (CMB). We show that the thermal effect dominates the kinematic effect and that the largest thermal decrements are associated with the most massive clusters in superclusters. Thus, searching for the presence of two or more close large CMB decrements represents a viable strategy for identifying superclusters at cosmological distances. Moreover, maps of the kinematic effect in superclusters are characterized by neighboring large peaks of opposite signs. These peaks can be as high as ~ 10 microK at the arcminute angular resolution. Simultaneous pointed observations of superclusters in the millimeter and submillimeter bands with upcoming sensitive CMB experiments can separate between the thermal and kinematic effect contributions and constrain the evolution of the velocity field in large overdense regions.Comment: 4 pages, 5 figures, ApJ Letters, in press; revised version according to referee's comment

Galaxy Clusters as mirrors of the distant Universe. Implications for the kSZ and ISW effects

It is well known that Thomson scattering of CMB photons in galaxy clusters introduces new anisotropies in the CMB radiation field, but however little attention is payed to the fraction of CMB photons that are scattered off the line of sight, causing a slight blurring of the CMB anisotropies present at the moment of scattering. In this work we study this {\it blurring} effect, and find that it has a non-negligible impact on estimations of the kinetic Sunyaev-Zel'dovich (kSZ) effect: it induces a 10% correction in 20-40% of the clusters/groups, and a 100% correction in $\sim 5$% of the clusters in an ideal (noiseless) experiment. We explore the possibility of using this blurring term to probe the CMB anisotropy field at different epochs in our Universe. In particular, we study the required precision in the removal of the kSZ that enables detecting the blurring term $-\tau_T \delta T / T_0$ in galaxy cluster populations placed at different redshift shells. By mapping this term in those shells, we would provide a tomographic probe for the growth of the Integrated Sachs Wolfe effect (ISW) during the late evolutionary stages of the Universe. We find that the required precision of the cluster peculiar velocity removal is of the order of 100 -- 200 km s$^{-1}$ in the redshift range 0.2 -- 0.8, after assuming that all clusters more massive than 10$^{14}$ h$^{-1}$ M$_{\odot}$ are observable. These errors are comparable to the total expected linear line of sight velocity dispersion for clusters in WMAPV cosmogony, and correspond to a residual level of roughly 900 -- 1800 $\tau_T \mu$K per cluster, including all types of contaminants and systematics. Were this precision requirement achieved, then independent constraints on the intrinsic cosmological dipole would be simultaneously provided.Comment: Notation clarified and typos and errors corrected in eqs.(2-4

Superclusters with thermal SZ effect surveys

We use a simple analytic model to compute the angular correlation function of clusters identified in upcoming thermal SZ effect surveys. We then compute the expected fraction of close pairs of clusters on the sky that are also close along the line of sight. We show how the expected number of cluster pairs as a function of redshift is sensitive to the assumed biasing relation between the cluster and the mass distribution. We find that, in a LambdaCDM model, the fraction of physically associated pairs is 70% for angular separations smaller than 20 arcmin and clusters with specific flux difference larger than 200 mJy at 143 GHz. The agreement of our analytic results with the Hubble volume N-body simulations is satisfactory. These results quantify the feasibility of using SZ surveys to compile catalogues of superclusters at any redshifts.Comment: 13 pages, 9 figures, submitted to MNRA