Indian ASTROSAT telescope set for global stardom
Nature 525, 7570 (2015). http://www.nature.com/doifinder/10.1038/525438a
Author: T. V. Padma
Observatory will extend the capabilities of existing US and European facilities, and boost Indian research.
The formation of submillimetre-bright galaxies from gas infall over a billion years
Nature 525, 7570 (2015). doi:10.1038/nature15383
Authors: Desika Narayanan, Matthew Turk, Robert Feldmann, Thomas Robitaille, Philip Hopkins, Robert Thompson, Christopher Hayward, David Ball, Claude-André Faucher-Giguère & Dušan Kereš
Submillimetre-bright galaxies at high redshift are the most luminous, heavily star-forming galaxies in the Universe and are characterized by prodigious emission in the far-infrared, with a flux of at least five millijanskys at a wavelength of 850 micrometres. They reside in haloes with masses about 1013 times that of the Sun, have low gas fractions compared to main-sequence disks at a comparable redshift, trace complex environments and are not easily observable at optical wavelengths. Their physical origin remains unclear. Simulations have been able to form galaxies with the requisite luminosities, but have otherwise been unable to simultaneously match the stellar masses, star formation rates, gas fractions and environments. Here we report a cosmological hydrodynamic galaxy formation simulation that is able to form a submillimetre galaxy that simultaneously satisfies the broad range of observed physical constraints. We find that groups of galaxies residing in massive dark matter haloes have increasing rates of star formation that peak at collective rates of about 500–1,000 solar masses per year at redshifts of two to three, by which time the interstellar medium is sufficiently enriched with metals that the region may be observed as a submillimetre-selected system. The intense star formation rates are fuelled in part by the infall of a reservoir gas supply enabled by stellar feedback at earlier times, not through major mergers. With a lifetime of nearly a billion years, our simulations show that the submillimetre-bright phase of high-redshift galaxies is prolonged and associated with significant mass buildup in early-Universe proto-clusters, and that many submillimetre-bright galaxies are composed of numerous unresolved components (for which there is some observational evidence).
Computational astrophysics: Monstrous galaxies unmasked
Nature 525, 7570 (2015). doi:10.1038/525465a
Authors: Romeel Davé
The enigma of how the most luminous galaxies arise is closer to being solved. New simulations show that these are long-lived massive galaxies powered by prodigious gas infall and the recycling of supernova-driven outflows. See Letter p.496
Planetary science: A balmy climate on exoplanets?
Nature 525, 7570 (2015). doi:10.1038/525429a
Certain planets outside our Solar System could have wind patterns that produce habitable climates.Ludmila Carone at the University of Leuven in Belgium and her team used climate models to investigate atmospheric temperatures and wind patterns on planets with Earth-like atmospheres. The chosen planets closely
Planetary science: Global ocean on Enceladus
Nature 525, 7570 (2015). doi:10.1038/525428a
Beneath an icy crust, Saturn's moon Enceladus (pictured) has an ocean that covers its entire globe.NASA's Cassini spacecraft measured wobbles in Enceladus's rotation over more than seven years. The data confirm that the crust is moving separately from the rocky core, meaning that there
The diurnal cycle of water ice on comet 67P/Churyumov–Gerasimenko
Nature 525, 7570 (2015). doi:10.1038/nature14869
Authors: M. C. De Sanctis, F. Capaccioni, M. Ciarniello, G. Filacchione, M. Formisano, S. Mottola, A. Raponi, F. Tosi, D. Bockelée-Morvan, S. Erard, C. Leyrat, B. Schmitt, E. Ammannito, G. Arnold, M. A. Barucci, M. Combi, M. T. Capria, P. Cerroni, W.-H. Ip, E. Kuehrt, T. B. McCord, E. Palomba, P. Beck & E. Quirico
Observations of cometary nuclei have revealed a very limited amount of surface water ice, which is insufficient to explain the observed water outgassing. This was clearly demonstrated on comet 9P/Tempel 1, where the dust jets (driven by volatiles) were only partially correlated with the exposed ice regions. The observations of 67P/Churyumov–Gerasimenko have revealed that activity has a diurnal variation in intensity arising from changing insolation conditions. It was previously concluded that water vapour was generated in ice-rich subsurface layers with a transport mechanism linked to solar illumination, but that has not hitherto been observed. Periodic condensations of water vapour very close to, or on, the surface were suggested to explain short-lived outbursts seen near sunrise on comet 9P/Tempel 1. Here we report observations of water ice on the surface of comet 67P/Churyumov–Gerasimenko, appearing and disappearing in a cyclic pattern that follows local illumination conditions, providing a source of localized activity. This water cycle appears to be an important process in the evolution of the comet, leading to cyclical modification of the relative abundance of water ice on its surface.