Search Publications

The HST view of FR I radio galaxies: evidence for non-thermal nuclear sources

Capetti, A.; Chiaberge, M.; Celotti, A.

Unresolved nuclear sources are detected by the Hubble Space Telescope in the great majority of a complete sample of 33 FR I radio galaxies belonging to the 3CR catalogue. The optical flux of these Central Compact Cores (CCC) shows a striking linear correlation with the radio core one over four decades, arguing for a non-thermal synchrotron origin …

Observations of Solid Carbon Dioxide in Molecular Clouds with the Infrared Space Observatory

de Graauw, Th.; Prusti, T.; van Dishoeck, E. F. +8 more

Spectra of interstellar CO₂ ice absorption features at a resolving power of λ/Δλ~1500-2000 are presented for 14 lines of sight. The observations were made with the Short-Wavelength Spectrometer (SWS) of the Infrared Space Observatory (ISO). Spectral coverage includes the primary stretching mode of CO₂ near 4.27 µm in al…

Source counts from the 15 mu m ISOCAM Deep Surveys

Aussel, H.; Elbaz, D.; Clements, D. L. +11 more

We present the results of the five mid-IR 15 mu m (12-18 mu m LW3 band) ISOCAM Guaranteed Time Extragalactic Surveys performed in the regions of the Lockman Hole and Marano Field. The roughly 1000 sources detected, 600 of which have a flux above the 80% completeness limit, guarantee a very high statistical significance for the integral and differe…

HUBBLE SPACE TELESCOPE/NICMOS Imaging of Disks and Envelopes around Very Young Stars

Brandner, Wolfgang; Stapelfeldt, Karl R.; Terebey, Susan +3 more

We present HST/NICMOS observations with ~0.1"~15 AU resolution of six young stellar objects in the Taurus star formation region. The targets of our survey are three Class I IRAS sources (IRAS 04016+2610, IRAS 04248+2612, and IRAS 04302+2247) and three low-luminosity stars (DG Tau B, Haro 6-5B, and CoKu Tau/1) associated with Herbig-Haro jets. The …

On the Doppler Shifts of Solar Ultraviolet Emission Lines

Peter, H.; Judge, P. G.

We examine emission-line profiles observed with the Solar Ultraviolet Measurement of Emitted Radiation (SUMER) instrument during the roll of the SOHO spacecraft on 1997 March 20. SUMER data were acquired in selected wavelength bands including lines from the low chromosphere to the corona. Our main aim is to determine the center-to-limb behavior of…

Metal Abundances at z<1.5: Fresh Clues to the Chemical Enrichment History of Damped Lyα Systems

Bowen, David V.; Pettini, Max; Ellison, Sara L. +1 more

We explore the redshift evolution of the metal content of damped Lyα systems (DLAs) with new observations of four absorbers at z<1.5 together with other recently published data, there is now a sample of 10 systems at intermediate redshifts for which the abundance of Zn has been measured. The main conclusion is that the column density-weighted m…

Solar Wind Outflow and the Chromospheric Magnetic Network

Dammasch, Ingolf E.; Wilhelm, Klaus; Curdt, Werner +5 more

Spectroscopic Constraints on Models of Ion Cyclotron Resonance Heating in the Polar Solar Corona and High-Speed Solar Wind

Kohl, John L.; Cranmer, Steven R.; Field, George B.

Using empirical ion velocity distributions derived from Ultraviolet Coronagraph Spectrometer (UVCS) and Solar Ultraviolet Measurements of Emitted Radiation (SUMER) ultraviolet spectroscopy, we construct theoretical models of the nonequilibrium plasma state of the polar solar corona. The primary energy deposition mechanism we investigate is the dis…

Far-Ultraviolet Radiation from Elliptical Galaxies

O'Connell, Robert W.

Far-ultraviolet radiation is a ubiquitous, if unanticipated, phenomenon in elliptical galaxies and early-type spiral bulges. It is the most variable photometric feature associated with old stellar populations. Recent observational and theoretical evidence shows that it is produced mainly by low-mass, small-envelope, helium-burning stars in extreme…

Three-dimensional Stereoscopic Analysis of Solar Active Region Loops. I. SOHO/EIT Observations at Temperatures of (1.0-1.5) × 10⁶ K

Klimchuk, J. A.; Aschwanden, Markus J.; Gary, G. Allen +5 more

The three-dimensional structure of solar active region NOAA 7986 observed on 1996 August 30 with the Extreme-Ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO) is analyzed. We develop a new method of dynamic stereoscopy to reconstruct the three-dimensional geometry of dynamically changing loops, which allows…