Search Publications
The structural and scaling properties of nearby galaxy clusters. II. The M-T relation
Arnaud, M.; Pointecouteau, E.; Pratt, G. W.
Using a sample of ten nearby (z≲ 0.15), relaxed galaxy clusters in the temperature range [2-9]~keV, we have investigated the scaling relation between the mass at various density contrasts (δ=2500,1000,500,200) and the cluster temperature. The masses are derived from NFW-type model fits to mass profiles, obtained under the hydrostatic assumption us…
Olivine and Pyroxene Diversity in the Crust of Mars
Mangold, N.; Bibring, J. -P.; Gendrin, A. +6 more
Data from the Observatoire pour la Minéralogie, l'Eau, les Glaces, et l'Activité (OMEGA) on the Mars Express spacecraft identify the distinct mafic, rock-forming minerals olivine, low-calcium pyroxene (LCP), and high-calcium pyroxene (HCP) on the surface of Mars. Olivine- and HCP-rich regions are found in deposits that span the age range of geolog…
Ion Neutral Mass Spectrometer Results from the First Flyby of Titan
Ip, Wing-Huen; McNutt, Ralph L.; Waite, J. Hunter +19 more
The Cassini Ion Neutral Mass Spectrometer (INMS) has obtained the first in situ composition measurements of the neutral densities of molecular nitrogen, methane, molecular hydrogen, argon, and a host of stable carbon-nitrile compounds in Titan's upper atmosphere. INMS in situ mass spectrometry has also provided evidence for atmospheric waves in th…
A planetary system as the origin of structure in Fomalhaut's dust belt
Kalas, Paul; Graham, James R.; Clampin, Mark
The Sun and >15per cent of nearby stars are surrounded by dusty disks that must be collisionally replenished by asteroids and comets, as the dust would otherwise be depleted on timescales <107years (ref. 1). Theoretical studies show that the structure of a dusty disk can be modified by the gravitational influence of planets, but t…
A Helium Spread among the Main-Sequence Stars in NGC 2808
D'Antona, F.; Bellazzini, M.; Galleti, S. +3 more
We have made a detailed study of the color distribution of the main sequence of the globular cluster (GC) NGC 2808, based on new deep HST WFPC2 photometry of a field in the uncrowded outskirts of the cluster. The observed color distribution of main-sequence stars is not Gaussian and is wider than expected for a single stellar population, given our…
The association of coronal mass ejections with their effects near the Earth
Schwenn, R.; Gonzalez, W. D.; Huttunen, E. +1 more
To this day, the prediction of space weather effects near the Earth suffers from a fundamental problem: The radial propagation speed of "halo" CMEs (i.e. CMEs pointed along the Sun-Earth-line that are known to be the main drivers of space weather disturbances) towards the Earth cannot be measured directly because of the unfavorable geometry. From …
The Centers of Early-Type Galaxies with Hubble Space Telescope. V. New WFPC2 Photometry
Filippenko, Alexei V.; Ho, Luis C.; Gebhardt, Karl +14 more
We present observations of 77 early-type galaxies imaged with the PC1 CCD of the Hubble Space Telescope (HST) WFPC2. ``Nuker-law'' parametric fits to the surface brightness profiles are used to classify the central structure into ``core'' or ``power-law'' forms. Core galaxies are typically rounder than power-law galaxies. Nearly all power-law gala…
The Mass Assembly Histories of Galaxies of Various Morphologies in the GOODS Fields
Conselice, Christopher J.; Ellis, Richard S.; Bundy, Kevin
We present an analysis of the growth of stellar mass with cosmic time partitioned according to galaxy morphology. Using a well-defined catalog of 2150 galaxies based, in part, on archival data in the Great Observatories Origins Deep Survey (GOODS) fields, we assign morphological types in three broad classes (ellipticals, spirals, peculiar/irregula…
Standard Photometric Systems
Bessell, Michael S.
Standard star photometry dominated the latter half of the twentieth century reaching its zenith in the 1980s. It was introduced to take advantage of the high sensitivity and large dynamic range of photomultiplier tubes compared to photographic plates. As the quantum efficiency of photodetectors improved and the wavelength range extended further to…
The nature and origin of Seyfert warm absorbers
Page, M. J.; Branduardi-Raymont, G.; Blustin, A. J. +2 more
We collate the results of recent high resolution X-ray spectroscopic observations of 23 AGN, and use the resulting information to try to provide answers to some of the main open questions about warm absorbers: where do they originate, what effect do they have on their host galaxies, and what is their importance within the energetics and dynamics o…