The diversity of quasars unified by accretion and orientation

Quasars are rapidly accreting supermassive black holes at the center of massive galaxies. They display a broad range of properties across all wavelengths, reflecting the diversity in the physical conditions of the regions close to the central engine. These properties, however, are not random, but form well-defined trends. The dominant trend is known as Eigenvector 1, where many properties correlate with the strength of optical iron and [OIII] emission. The main physical driver of Eigenvector 1 has long been suspected to be the quasar luminosity normalized by the mass of the hole (the Eddington ratio), an important quantity of the black hole accretion process. But a definitive proof has been missing. Here we report an analysis of archival data that reveals that Eddington ratio indeed drives Eigenvector 1. We also find that orientation plays a significant role in determining the observed kinematics of the gas, implying a flattened, disklike geometry for the fast-moving clouds close to the hole. Our results show that most of the diversity of quasar phenomenology can be unified with two simple quantities, Eddington ratio and orientation.Comment: This is the author's version of the work; 18 pages including Supplementary Information; to appear in the 11 September 2014 issue of Nature at http://dx.doi.org/10.1038/nature1371

Aging vs crystallisation dynamics in hyperquenched glasses and a resolution of the water Tg controversy

The possibility of observing a glass transition in water before crystallisation occurs has been debated vigorously but inconclusively over five decades [1,2]. For two decades a glass transition at 136K [2,3] was accepted but this transition has perplexing qualities [4]. Recently it has been argued[2,5],that this assignment must be wrong. The re-assignment of Tg to temperatures above the 150K crystallisation was vigorously contested [6]. Here we use detailed anneal-and-scan studies of a hyperquenched inorganic glass, which does not crystallize on heating, to interpret the perplexing aspects of the 136K water phenomenon. We show that it is indeed linked to a glass transition, though only via a cross-over phenomenon. The thermal history that gives the same behaviour ("shadow" glass transition) in the inorganic glass is linked by crossover to a "normal" glass transition 23% higher in temperature. Thus a Tg is indeed unobservable for water, while the vitreous nature of hyperquenched glassy water is strongly supported. The shadow Tg is reproducible in the inorganic glass as it is in H2O. The observed aging dynamics are very relevant to current glass theory, particularly to dynamical heterogeneity which is seen to have an energy manifestation.Comment: 23 pages, 4 figure

The Tariff Equivalent and Forgone Trade Effects of Prohibitive Technical Barriers to Trade

We derive a method to econometrically estimate the tariff equivalent and foregone trade effects of a prohibitive technical barrier to trade (TBT) based on Wales and Woodland's Kuhn-Tucker approach to corner solutions in consumer choice. The method overcomes the lack of observed data on bilateral trade flows and accounts for differentiated goods by place of origin. We apply the derived random utility model to international trade in apples to identify the tariff equivalent of prohibitive nontariff trade barriers imposed by Australia on potential imports of New Zealand apples. We estimate the forgone apple trade between the two countries, the implied trade injury imposed by Australia on New Zealand, and the welfare loss to Australia. The removal of the TBTs would induce net welfare gains around US$50 million annually for Australia.Corner solution; Kuhn-Tucker model; New Zealand apples; nontariff barrier; NTB; prohibitive; random utility; TBT; technical barrier to trade; SPS; phytosanitary