Search Publications
Discovery of 10 µm silicate emission in quasars. Evidence of the AGN unification scheme
Siebenmorgen, R.; Schulz, B.; Haas, M. +1 more
According to the unified scheme, AGN are surrounded by a dust-torus, and the observed diversity of AGN properties results from the different orientations relative to our line of sight. The strong resonance of silicate dust at 10 µm is therefore, as expected, seen in absorption towards many type-2 AGN. In type-1 AGN, it should be seen in emis…
Spitzer imaging of i'-drop galaxies: old stars at z~ 6
Bunker, Andrew J.; Ellis, Richard S.; Stanway, Elizabeth R. +3 more
We present new evidence for mature stellar populations with ages >100Myr in massive galaxies (Mstellar > 1010Msolar) seen at a time when the Universe was less than 1Gyr old. We analyse the prominent detections of two z~ 6 star-forming galaxies (SBM03#1 and #3) made at wavelengths corresponding to the rest-fra…
Evidence from the Mars Express High Resolution Stereo Camera for a frozen sea close to Mars' equator
HRSC Co-Investigator Team; Head, James W.; van Gasselt, Stephan +10 more
It is thought that the Cerberus Fossae fissures on Mars were the source of both lava and water floods two to ten million years ago. Evidence for the resulting lava plains has been identified in eastern Elysium, but seas and lakes from these fissures and previous water flooding events were presumed to have evaporated and sublimed away. Here we pres…
Can the Steep Mass Profile of A1689 Be Explained by a Triaxial Dark Halo?
Broadhurst, Tom; Oguri, Masamune; Umetsu, Keiichi +1 more
The steep mass profile of A1689 derived from recent detailed lensing observations is not readily reconciled with the low-concentration halos predicted by the standard cold dark matter (CDM) model. However, halo triaxiality may act to bias the profile constraints derived assuming a spherically symmetric mass distribution, since lensing relates only…
Hubble Space Telescope Observations of Element Abundances in Low-Redshift Damped Lyα Galaxies and Implications for the Global Metallicity-Redshift Relation
York, Donald G.; Fall, S. Michael; Kulkarni, Varsha P. +4 more
Most models of cosmic chemical evolution predict that the mass-weighted mean interstellar metallicity of galaxies should rise with time from a low value ~1/30 solar at z~3 to a nearly solar value at z=0. In the absence of any selection effects, the damped Lyα absorbers (DLAs) in quasar spectra are expected to show such a rise in global metallicity…
The Low-z Intergalactic Medium. I. O VI Baryon Census
Shull, J. Michael; Danforth, Charles W.
Intergalactic absorbers along lines of sight to distant quasars are a powerful diagnostic for the evolution and content of the intergalactic medium (IGM). In this study, we use the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite to search 129 known Lyα absorption systems at z<0.15 toward 31 active galactic nuclei (AGNs) for correspondin…
The vertical profile of winds on Titan
Plettemeier, D.; Gurvits, L. I.; Pogrebenko, S. V. +12 more
One of Titan's most intriguing attributes is its copious but featureless atmosphere. The Voyager 1 fly-by and occultation in 1980 provided the first radial survey of Titan's atmospheric pressure and temperature and evidence for the presence of strong zonal winds. It was realized that the motion of an atmospheric probe could be used to study the wi…
Coronal Evolution of the Sun in Time: High-Resolution X-Ray Spectroscopy of Solar Analogs with Different Ages
Skinner, Stephen L.; Güdel, Manuel; Ness, Jan-Uwe +3 more
We investigate the long-term evolution of X-ray coronae of solar analogs based on high-resolution X-ray spectroscopy and photometry with XMM-Newton. Six nearby main-sequence G stars with ages between ~0.1 and ~1.6 Gyr and rotation periods between ~1 and 12.4 days have been observed. We use the X-ray spectra to derive coronal element abundances of …
VLT spectroscopy of globular cluster systems. II. Spectroscopic ages, metallicities, and [ α/Fe] ratios of globular clusters in early-type galaxies
Saglia, R. P.; Thomas, D.; Bender, R. +5 more
An analysis of ages, metallicities, and [ α/Fe] ratios of globular cluster systems in early-type galaxies is presented, based on Lick index measurements summarized in Puzia et al. (2004, A&A, 415, 123, Paper I of this series). In the light of calibration and measurement uncertainties, age-metallicity degeneracy, and the relative dynamic range …
Reconnection in a rotation-dominated magnetosphere and its relation to Saturn's auroral dynamics
Jackman, C. M.; Milan, S. E.; Yeoman, T. K. +6 more
The first extended series of observations of Saturn's auroral emissions, undertaken by the Hubble Space Telescope in January 2004 in conjunction with measurements of the upstream solar wind and interplanetary magnetic field (IMF) by the Cassini spacecraft, have revealed a strong auroral response to the interplanetary medium. Following the arrival …