University of Victoria

About: University of Victoria is a education organization based out in Victoria, British Columbia, Canada. It is known for research contribution in the topics: Population & Galaxy. The organization has 14994 authors who have published 41051 publications receiving 1447972 citations. The organization is also known as: Victoria College.

The thermal imprint of galaxy formation on X-ray clusters

Abstract: It is widely believed that structure in the Universe evolves hierarchically—fluctuations in the primordial distribution of matter, amplified by gravity, collapse and merge to form progressively larger systems, culminating in the clusters of galaxies that are observed today. But the observed structure and evolution of X-ray-emitting clusters of galaxies seems to be at odds with this picture1. In particular, clusters and groups with relatively few galaxies, as well as most distant clusters, are substantially fainter in X-rays than predicted by models of hierarchical formation. Here we show that these discrepancies arise because the entropy of the hot diffuse intracluster gas near the centre of the cluster is higher than can be explained by gravitational collapse alone. We argue that the excess entropy is a relic of the energetic winds generated by supernovae in the forming galaxies. These winds also enriched the intracluster medium with elements heavier than helium. We show that such a process can account for the observed effects only if the intracluster medium is heated at modest redshifts (z ≲ 2) but before the final collapse into a cluster structure, indicating that the formation of galaxies precedes that of clusters and that most clusters have been assembled very recently.

Warming asymmetry in climate change simulations

Abstract: Climate change simulations made with coupled global climate models typically show a marked hemispheric asymmetry with more warming in the northern high latitudes than in the south. This asymmetry is ascribed to heat uptake by the ocean at high southern latitudes. A recent version of the CCCma climate model exhibits a much more symmetric warming, compared to an earlier version, and agrees somewhat better with observed 20th century trends. This is associated with an improved parameterization of ocean mixing which results in a decrease in heat penetration into the Southern Ocean, in accord with earlier ocean-only and simple coupled model investigations. The global average warming and the net penetration of heat into the global ocean (and hence its thermal expansion) are essentially unchanged. Observed trends in sea-ice extent over the past two decades exhibit hemispheric asymmetry with a statistically significant decrease in northern but not in southern ice cover. Both model versions are consistent with these observations implying that observed ice extent is not yet an indicator of asymmetry in future global warming. Taken together, these results suggest that southern hemisphere climate warming at a rate comparable to that in the northern hemisphere should be considered a realistic possiblity.

Improved luminosity determination in pp collisions at root s=7 TeV using the ATLAS detector at the LHC

Abstract: The luminosity calibration for the ATLAS detector at the LHC during pp collisions at root s = 7 TeV in 2010 and 2011 is presented. Evaluation of the luminosity scale is performed using several luminosity-sensitive detectors, and comparisons are made of the long-term stability and accuracy of this calibration applied to the pp collisions at root s = 7 TeV. A luminosity uncertainty of delta L/L = +/- 3.5 % is obtained for the 47 pb(-1) of data delivered to ATLAS in 2010, and an uncertainty of delta L/L = +/- 1.8 % is obtained for the 5.5 fb(-1) delivered in 2011.

Drought in the Anthropocene

Abstract: Drought management is inefficient because feedbacks between drought and people are not fully understood. In this human-influenced era, we need to rethink the concept of drought to include the human role in mitigating and enhancing drought.