Australian National University

About: Australian National University is a education organization based out in Canberra, Australian Capital Territory, Australia. It is known for research contribution in the topics: Population & Galaxy. The organization has 34419 authors who have published 109261 publications receiving 4315448 citations. The organization is also known as: The Australian National University & ANU.

An expanded Mbh–σ diagram, and a new calibration of active galactic nuclei masses

Abstract: We present an updated and improved Mbh–σ diagram containing 64 galaxies for which Mbh measurements (not just upper limits) are available. Because of new and increased black hole masses at the high-mass end, and a better representation of barred galaxies at the low-mass end, the ‘classical’ (all morphological type) Mbh–σ relation for predicting black hole masses is log (Mbh/M⊙) = (8.13 ± 0.05) + (5.13 ± 0.34)log [σ/200 km s−1], with an rms scatter of 0.43 dex. Modifying the regression analysis to correct for a hitherto overlooked sample bias in which black holes with masses <106 M⊙ are not (yet) detectable, the relation steepens further to give log (Mbh/M⊙) = (8.15 ± 0.06) + (5.95 ± 0.44)log [σ/200 km s−1]. We have also updated the ‘barless’ and ‘elliptical-only’Mbh–σ relations introduced by Graham and Hu in 2008 due to the offset nature of barred galaxies. These relations have a total scatter as low as 0.34 dex and currently define the upper envelope of points in the Mbh–σ diagram. They also have a slope consistent with a value 5, in agreement with the prediction by Silk & Rees based on feedback from massive black holes in bulges built by monolithic collapse. Using updated virial products and velocity dispersions from 28 active galactic nuclei, we determine that the optimal scaling factor f– which brings their virial products in line with the 64 directly measured black hole masses – is 2.8+0.7−0.5. This is roughly half the value reported by Onken et al. and Woo et al., and consequently halves the mass estimates of most high-redshift quasars. Given that barred galaxies are, on average, located ∼0.5 dex below the ‘barless’ and ‘elliptical-only’Mbh–σ relations, we have explored the results after separating the samples into barred and non-barred galaxies, and we have also developed a preliminary corrective term to the velocity dispersion based on bar dynamics. In addition, given the recently recognized coexistence of massive black holes and nuclear star clusters, we present the first ever (Mbh+Mnc)–σ diagram and begin to explore how galaxies shift from their former location in the Mbh–σ diagram.

New four-million-year-old hominid species from Kanapoi and Allia Bay, Kenya

Abstract: Nine hominid dental, cranial and postcranial specimens from Kanapoi, Kenya, and 12 specimens from Allia Bay, Kenya, are described here as a new species of Australopithecus dating from between about 3.9 million and 4.2 million years ago. The mosaic of primitive and derived features shows this species to be a possible ancestor to Australopithecus afarensis and suggests that Ardipithecus ramidus is a sister species to this and all later hominids. A tibia establishes that hominids were bipedal at least half a million years before the previous earliest evidence showed.

Temperature sensitivity of soil respiration rates enhanced by microbial community response

Abstract: Soils store about four times as much carbon as plant biomass, and soil microbial respiration releases about 60 petagrams of carbon per year to the atmosphere as carbon dioxide. Short-term experiments have shown that soil microbial respiration increases exponentially with temperature. This information has been incorporated into soil carbon and Earth-system models, which suggest that warming-induced increases in carbon dioxide release from soils represent an important positive feedback loop that could influence twenty-first-century climate change. The magnitude of this feedback remains uncertain, however, not least because the response of soil microbial communities to changing temperatures has the potential to either decrease or increase warming-induced carbon losses substantially. Here we collect soils from different ecosystems along a climate gradient from the Arctic to the Amazon and investigate how microbial community-level responses control the temperature sensitivity of soil respiration. We find that the microbial community-level response more often enhances than reduces the mid- to long-term (90 days) temperature sensitivity of respiration. Furthermore, the strongest enhancing responses were observed in soils with high carbon-to-nitrogen ratios and in soils from cold climatic regions. After 90 days, microbial community responses increased the temperature sensitivity of respiration in high-latitude soils by a factor of 1.4 compared to the instantaneous temperature response. This suggests that the substantial carbon stores in Arctic and boreal soils could be more vulnerable to climate warming than currently predicted.

A Comparative Study of Inequality and Corruption

Abstract: We propose that income inequality increases corruption. The rich are likely to both have greater motivation and opportunities to engage in bribery and fraud as one means to preserve and advance their status, privileges, and interests while the poor are more vulnerable to extortion at higher levels of inequality. While countries with authoritarian regimes are likely to have greater levels of corruption on average, the effect of greater inequality on corruption will be higher in democracies, in which the wealthy cannot employ repression and poorer groups are likely to more effectively demand redistribution. Both OLS estimates (for samples of 95 to 122 countries) and IV 2SLS estimates (for samples of 83 to 103 countries) support our arguments, with 2SLS estimates showing stronger statistically significant effects of inequality on corruption, utilizing Transparency International's Corruption Perceptions Index, the World Bank's Control of Corruption Index (average for 1996-2002) and Dollar and Kraay's income inequality data (average Gini for 1950-1999). Surprisingly, the explanatory power of inequality is substantially no less important than conventionally accepted causes of corruption such as economic development. Contrary to conventional wisdom, smaller and not larger government is associated with higher levels of corruption, because higher inequality through corruption is associated with lower tax rates as well as lower government transfers and subsidies.