Search Publications
H_2 emission from shocks in molecular outflows: the significance of departures from a stationary state
Pineau des Forêts, G.; Flower, D. R.
We have computed the time dependence of the H_2 rovibrational emission spectrum from molecular outflows. This emission arises in shock waves generated by the impact of jets, associated with low-mass star formation, on molecular gas. The shocks are unlikely to have attained a state of equilibrium, and so their structure will exhibit both C- and J-t…
Infrared spectra of young stars in Chamaeleon
Henning, Th.; Lemke, D.; Pfau, W. +2 more
We present infrared spectra covering the wavelength ranges 3.1-5.0 mu m and 5.8-11.6 mu m for 9 young stars located in the Chamaeleon I dark cloud. The spectra were taken with the spectrophotometer of ISO (ISOPHOT-S). The spectra of three stars which illuminate reflection nebulae are dominated by the series of strong emission features generally as…
ISO-SWS spectroscopy of IC443 and the origin of the IRAS 12 and 25 MU M emission from radiative supernova remnants
Lutz, D.; Oliva, E.; Moorwood, A. F. M. +1 more
ISO-SWS spectral observations of the supernova remnant IC443 are presented. Like other radiative SNRs, this object is characterized by prominent line-emitting filaments and relatively strong IRAS 12 and 25 mu m emission which is commonly interpreted as thermal radiation from very small grains stochastically heated by collisions with the hot plasma…
Objects in NGC 205 Resolved into Stellar Associations by Hubble Space Telescope Ultraviolet Imaging
Cappellari, Michele; Renzini, Alvio; Greggio, Laura +3 more
We have obtained high-resolution UV images with the Hubble Space Telescope/Wide-Field Planetary Camera 2 of the central region of the dwarf elliptical galaxy NGC 205. Our images reveal that many of the hot UV stars previously detected and studied from the ground are actually multiple systems, open clusters, and star associations. We have performed…
The Host Galaxy of the Broad Absorption Line QSO PG 1700+518 and Its Ring Galaxy Companion: NICMOS 1.6 Micron Imaging
Hines, Dean C.; Thompson, Rodger I.; Weymann, Ray J. +2 more
The 1.6 µm Near Infrared Camera and Multiobject Spectrometer image of the broad absorption line QSO PG 1700+518 clearly resolves the QSO host galaxy and a ringlike companion. The companion is most likely a ring galaxy produced in a collision with the QSO galaxy ~5×107 yr ago. The morphology of the PG 1700+518 system is very simila…
A Precision Test of HIPPARCOS Systematics toward the Hyades
Gould, Andrew; Narayanan, Vijay K.
We propose a test that can in principle detect any systematic errors in the Hipparcos parallaxes toward the Hyades cluster at the level of 0.3 mas. We show that the statistical parallax algorithm subsumes the classical moving cluster methods and provides more precise estimates of the distance and the first two moments of the velocity distribution …
A search for star formation in the translucent clouds MBM7 and MBM55
Schmitt, J. H. M. M.; Neuhäuser, R.; Caillault, J. -P. +3 more
The star formation capability of two molecular clouds at high galactic latitude ( | b | > 30(deg) ) is investigated. Possible pre-main sequence stars in and around the translucent clouds MBM7 and MBM55 have been identified via their X-ray emission by inspecting ROSAT All-Sky Survey observations of the clouds and environs and ROSAT pointed obser…
Solar wind stream interfaces in corotating interaction regions: New SWICS/Ulysses results
Wimmer-Schweingruber, Robert F.; von Steiger, Rudolf; Paerli, Raoul
We have analyzed data from the solar wind ion composition spectrometer (SWICS)/Ulysses instrument taken between August 1996 and May 1997. In this period the Ulysses spacecraft traveled from 28° to 11°N and encountered a highly regular pattern of high-speed streams alternating with slow solar wind. Heliocentric distance varied between 4.3 and 5.1 a…
Multi-wavelength observations of the onset phase of a coronal mass ejection
Thompson, B. J.; Inhester, B.; Harrison, R. A. +6 more
The structure and dynamics of the initial phases of a coronal mass ejection (CME) seen in soft X-ray, extreme ultraviolet and optical emission are described. The event occurred on the SW limb of the Sun in active region AR 8026 on 9 April 1997. Just prior to the CME there was a class C1.5 flare. Images taken with the Extreme Ultraviolet Imaging Te…
The Color Distributions of Globular Clusters in Virgo Elliptical Galaxies
Tsvetanov, Zlatan I.; Neilsen, Eric H., Jr.
This Letter presents the color distributions of the globular cluster (GC) systems of 12 Virgo elliptical galaxies, measured using data from the Hubble Space Telescope. Bright galaxies with large numbers of detected GCs show two distinct cluster populations with mean V-I colors near 1.01 and 1.26. The GC population of M86 is a clear exception; its …