The CERN Axion Solar Telescope (CAST) has extended its search for solar axions by using (3)He as a buffer gas. At T=1.8 K this allows for larger pressure settings and hence sensitivity to higher axion masses than our previous measurements with (4)He. With about 1 h of data taking at each of 252 different pressure settings we have scanned the axion mass range 0.39 eV≲m(a)≲0.64 eV. From the absence of excess x rays when the magnet was pointing to the Sun we set a typical upper limit on the axion-photon coupling of g(aγ)≲2.3×10(-10) GeV(-1) at 95% C.L., the exact value depending on the pressure setting. Kim-Shifman-Vainshtein-Zakharov axions are excluded at the upper end of our mass range, the first time ever for any solar axion search. In the future we will extend our search to m(a)≲1.15 eV, comfortably overlapping with cosmological hot dark matter bounds.

We present results from recent Suzaku and Chandra X-ray, and MMT optical observations of the strongly merging "double cluster" A1750 out to its virial radius, both along and perpendicular to a putative large-scale structure filament. Some previous studies of individual clusters have found evidence for ICM entropy profiles that flatten at large cluster radii, as compared with the self-similar prediction based on purely gravitational models of hierarchical cluster formation, and gas fractions that rise above the mean cosmic value. Weakening accretion shocks and the presence of unresolved cool gas clumps, both of which are expected to correlate with large scale structure filaments, have been invoked to explain these results. In the outskirts of A1750, we find entropy profiles that are consistent with self-similar expectations, and gas fractions that are consistent with the mean cosmic value, both along and perpendicular to the putative large scale filament. Thus, we find no evidence for gas clumping in the outskirts of A1750, in either direction. This may indicate that gas clumping is less common in lower temperature (kT ≈ 4 keV), less massive systems, consistent with some (but not all) previous studies of low mass clusters and groups. Cluster mass may therefore play a more important role in gas clumping than dynamical state. Finally, we find evidence for diffuse, cool (< 1 keV) gas at large cluster radii (R 200 ) along the filament, which is consistent with the expected properties of the denser, hotter phase of the WHIM.

The spatial distribution of the metals residing in the intra-cluster medium (ICM) of galaxy clusters records all the information on a cluster's nucleosynthesis and chemical enrichment history. We present measurements from a total of 1.2Ms Suzaku XIS and 72ks Chandra observations of the cool-core galaxy cluster Abell 3112 out to its virial radius (∼1470 kpc). We find that the ratio of the observed supernova type Ia explosions to the total supernova explosions has a uniform distribution at a level of 12%-16% out to the cluster's virial radius. The observed fraction of type Ia supernova explosions is in agreement with the corresponding fraction found in our Galaxy and the chemical enrichment of our Galaxy. The non-varying supernova enrichment suggests that the ICM in cluster outskirts was enriched by metals at an early stage before the cluster itself was formed during a period of intense star formation activity. Additionally, we find that the 2D delayed detonation model CDDT produce significantly worse fits to the X-ray spectra compared to simple 1D W7 models. This is due to the relative overestimate of Si, and the underestimate of Mg in these models with respect to the measured abundances.

In this paper, we report the relative supernovae (SNe) contribution to the metal budget of the intracluster medium (ICM) of the Abell 1837 galaxy cluster at redshift z = 0.069. For this purpose, we analysed the hot ICM of the cluster and obtained radial metal distributions using XMM–Newton archival data with a total exposure of ∼100 ks. These metal measurements consist of Mg, Si, S, Fe and Ni within a radius of 0.7 R500, which is divided into three concentric annuli. In order to explain the observed metal abundance pattern in terms of relative supernova contributions, we used our newly developed code SNeRatio, which utilizes theoretical nucleosynthesis models. This study covers the most recent 3D Type Ia SN and core-collapse SN yield tables. All combinations of these theoretical yields were fitted with our measured abundance ratios, and statistically acceptable ones were selected. Each of these models was found to predict a uniform SNIa percentage contribution to the total SNe from the cluster centre to the outskirts and to form an SNIa ratio distribution with a mean of 39 ± 14${{\ \rm per\ cent}}$. This uniformity is consistent with the early enrichment scenario, which assumes that metal production processes begin in the early phase of cluster formation, namely the proto-cluster phase at epoch z ≥ 2.