Search Publications
Titan's methane cycle
Atreya, Sushil K.; Ferri, Francesca; Niemann, Hasso B. +5 more
Methane is key to sustaining Titan's thick nitrogen atmosphere. However, methane is destroyed and converted to heavier hydrocarbons irreversibly on a relatively short timescale of approximately 10-100 million years. Without the warming provided by CH 4-generated hydrocarbon hazes in the stratosphere and the pressure induced opacity in t…
Origin of the Galactic ridge X-ray emission
Sunyaev, R.; Revnivtsev, M.; Sazonov, S. +2 more
We analyze a map of the Galactic ridge X-ray emission (GRXE) constructed in the 3-20 keV energy band from RXTE/PCA scan and slew observations. We show that the GRXE intensity follows the Galactic near-infrared surface brightness closely and thus traces the Galactic stellar mass distribution. The GRXE consists of two spatial components that can be …
The colours of the Sun
Flynn, Chris; Holmberg, Johan; Portinari, Laura
We compile a sample of Sun-like stars with accurate effective temperatures, metallicities and colours (from the ultraviolet to the near-infrared). A crucial improvement is that the effective temperature scale of the stars has recently been established as both accurate and precise through direct measurement of angular diameters obtained with stella…
Chandra and XMM-Newton Observations of a Sample of Low-Redshift FR I and FR II Radio Galaxy Nuclei
Hardcastle, M. J.; Birkinshaw, M.; Worrall, D. M. +2 more
We present spectral results from Chandra and XMM-Newton observations of a sample of 22 low-redshift (z<0.1) radio galaxies and consider whether the core emission originates from the base of a relativistic jet, or an accretion flow, or contains contributions from both. We find correlations between the unabsorbed X-ray, radio, and optical fluxes …
Hubble Space Telescope and Ground-based Observations of Type Ia Supernovae at Redshift 0.5: Cosmological Implications
Filippenko, Alexei V.; Garnavich, Peter; Riess, Adam G. +26 more
We present observations of the Type Ia supernovae (SNe) 1999M, 1999N, 1999Q, 1999S, and 1999U, at redshift z~0.5. They were discovered in early 1999 with the 4.0 m Blanco telescope at Cerro Tololo Inter-American Observatory by the High-z Supernova Search Team (HZT) and subsequently followed with many ground-based telescopes. SNe 1999Q and 1999U we…
Early and Rapid Merging as a Formation Mechanism of Massive Galaxies: Empirical Constraints
Conselice, Christopher J.
We present the results of a series of empirical computations regarding the role of major mergers in forming the stellar masses of modern galaxies based on measured galaxy merger and star formation histories from z~0.5 to 3. We reconstruct the merger history of normal field galaxies from z~3 to z~0 as a function of initial mass using published pair…
Composition and Physical Properties of Enceladus' Surface
Sotin, C.; Baines, K. H.; Nicholson, P. D. +22 more
Observations of Saturn's satellite Enceladus using Cassini's Visual and Infrared Mapping Spectrometer instrument were obtained during three flybys of Enceladus in 2005. Enceladus' surface is composed mostly of nearly pure water ice except near its south pole, where there are light organics, CO2, and amorphous and crystalline water ice, …
Joint observations by Cluster satellites of bursty bulk flows in the magnetotail
Zhang, T. L.; Dandouras, I.; Lucek, E. +9 more
Using the observations of three satellites of Cluster (C1, C3, and C4) during the periods July to October 2001 and July to October 2002, we study 209 active time bursty bulk flows (BBFs), the difference between single satellite observations and multisatellite observations, and the difference among three selection criteria (two about BBFs and one a…
Hubble Space Telescope NICMOS Observations of T Dwarfs: Brown Dwarf Multiplicity and New Probes of the L/T Transition
Burrows, Adam; Kirkpatrick, J. Davy; Burgasser, Adam J. +5 more
We present the results of a Hubble Space Telescope NICMOS imaging survey of 22 T-type field brown dwarfs. Five are resolved as binary systems with angular separations of 0.05"-0.35", and companionship is established on the basis of component F110W-F170M colors (indicative of CH4 absorption) and low probabilities of background contaminat…
The Latitudinal Distribution of Clouds on Titan
Montmessin, F.; Lebonnois, S.; Rannou, P. +1 more
Clouds have been observed recently on Titan, through the thick haze, using near-infrared spectroscopy and images near the south pole and in temperate regions near 40°S. Recent telescope and Cassini orbiter observations are now providing an insight into cloud climatology. To study clouds, we have developed a general circulation model of Titan that …