On the Presence of Thermal SZ Induced Signal in the First Year WMAP Temperature Maps

Using available optical and X-ray catalogues of clusters and superclusters of galaxies, we build templates of tSZ emission as they should be detected by the WMAP experiment. We compute the cross-correlation of our templates with WMAP temperature maps, and interpret our results separately for clusters and for superclusters of galaxies. For clusters of galaxies, we claim 2-5 $\sigma$ detections in our templates built from BCS Ebeling et al. (1998), NORAS (Boehringer et al. 2000) and de Grandi et al. (1999) catalogues. In these templates, the typical cluster temperature decrements in WMAP maps are around 15-35 $\mu$K in the RJ range (no beam deconvolution applied). Several tests probing the possible influence of foregrounds in our analyses demonstrate that our results are robust against galactic contamination. On supercluster scales, we detect a diffuse component in the V & W WMAP bands which cannot be generated by superclusters in our catalogues (Einasto et al. 1994, 1997), and which is not present in the clean map of Tegmark, de Oliveira-Costa & Hamilton (2003). Using this clean map, our analyses yield, for Einasto's supercluster catalogues, the following upper limit for the comptonization parameter associated to supercluster scales: y_{SC} < 2.18 \time s 10^{-8} at the 95% confidence limit.Comment: MNRAS accepted. New section and minor changes include

Limits on Hot Intracluster Gas Contributions to the Tenerife Temperature Anisotropy Map

We limit the contribution of the hot intracluster gas, by means of the Sunyaev-Zel'dovich effect, to the temperature anisotropies measured by the Tenerife experiment. The data is cross-correlated with maps generated from the ACO cluster catalogue, the ROSAT PSPC catalogue of clusters of galaxies, a catalogue of superclusters and the HEAO 1 A-1 map of X-ray sources. There is no evidence of contamination by such sources at an rms level of $\sim 8\mu$K at 99% confidence level at $5^o$ angular resolution. We place an upper limit on the mean Comptonization parameter of $y \le 1.5\times 10^{-6}$ at the same level of confidence. These limits are slightly more restrictive than those previously found by a similar analysis on the COBE/DMR data and indicate that most of the signal measured by Tenerife is cosmological.Comment: To be published in ApJ (main journal

Inverse magnetic catalysis from the properties of the QCD coupling in a magnetic field

We compute the vacuum one-loop quark-gluon vertex correction at zero temperature in the presence of a magnetic field. From the vertex function we extract the effective quark-gluon coupling and show that it grows with increasing magnetic field strength. The effect is due to a subtle competition between the color charge associated to gluons and the color charge associated to quarks, the former being larger than the latter. In contrast, at high temperature the effective thermo-magnetic coupling results exclusively from the contribution of the color charge associated to quarks. This produces a decrease of the coupling with increasing field strength. We interpret the results in terms of a geometrical effect whereby the magnetic field induces, on average, a closer distance between the (electrically charged) quarks and antiquarks. At high temperature, since the effective coupling is proportional only to the color charge associated to quarks, such proximity with increasing field strength makes the effective coupling decrease due to asymptotic freedom. In turn, this leads to a decreasing quark condensate. In contrast, at zero temperature both the effective strong coupling and the quark condensate increase with increasing magnetic field. This is due to the color charge associated to gluons dominating over that associated to quarks, with both having the opposite sign. Thus, the gluons induce a kind of screening of the quark color charge, in spite of the quark-antiquark proximity. The implications of these results for the inverse magnetic catalysis phenomenon are discussed.Comment: Expanded discussion, references added. Version to appear in Phys. Lett.

Wide binaries as a critical test for Gravity theories

Assuming Newton's gravity and GR to be valid at all scales leads to the dark matter hypothesis as a requirement demanded by the observed dynamics and measured baryonic content at galactic and extragalactic scales. Alternatively, modified gravity scenarios where a change of regime appears at acceleration scales $a<a_{0}$ have been proposed. This modified regime at $a<a_{0}$ will generically be characterised by equilibrium velocities which become independent of distance. Here we identify a critical test in this debate and we propose its application to samples of wide binary stars. Since for $1 M_{\odot}$ systems the acceleration drops below $a_{0}$ at scales of around 7000 AU, a statistical survey of wide binaries with relative velocities and separations reaching $10^{4}$ AU and beyond should prove useful to the above debate. We apply the proposed test to the best currently available data. Results show a constant upper limit to the relative velocities in wide binaries which is independent of separation for over three orders of magnitude, in analogy with galactic flat rotation curves in the same $a<a_{0}$ acceleration regime. Our results are suggestive of a breakdown of Kepler's third law beyond $a \approx a_{0}$ scales, in accordance with generic predictions of modified gravity theories designed not to require any dark matter at galactic scales and beyond.Comment: 4 pages 1 figure, Proceedings of the COSGRAV12 meeting, Kolkata, India, 7th - 11th February, 201