Search Publications

The Centers of Early- to Intermediate-Type Spiral Galaxies: A Structural Analysis

Carollo, C. Marcella

A recent Hubble Space Telescope (HST)/WFPC2 visual survey of early- and intermediate-type spiral galaxies has unveiled a great complexity in the inner regions of these systems, which include a high fraction of photometrically distinct compact sources sitting at the galactic centers (``nuclei''). The faint nuclei (M_V>~-12) are typical…

Evidence for Chromospheric Evaporation in the Late Gradual Flare Phase from SOHO/CDS Observations

De Pontieu, B.; Czaykowska, A.; Alexander, D. +1 more

Using extreme-ultraviolet (EUV) spectroheliograms from the first intentional postflare observations with the Coronal Diagnostic Spectrometer (CDS) on board SOHO, we determine relative line-of-sight velocities and their temporal evolution during the gradual flare phase of an M6.8 two-ribbon flare that occurred on 1998 April 29. Dopplergrams in line…

The ISO spectrum of the young star HD 142527

Waters, L. B. F. M.; de Koter, A.; Waelkens, C. +2 more

We present a detailed analysis of SWS (2.35-45 mu m) and LWS (43-200 mu m) spectra obtained with the Infrared Space Observatory (ISO) (Kessler et al. 1996) of the dusty circumstellar disk surrounding the isolated young Fe star HD 142527. Two dust populations can be clearly discriminated: a warm component which is dominated by very strong silicate …

Laboratory studies of thermally processed H_2O-CH_3OH-CO_2 ice mixtures and their astrophysical implications

van Dishoeck, E. F.; Whittet, D. C. B.; Schutte, W. A. +7 more

Data of the Infrared Space Observatory ISO have strongly influenced the current view of interstellar ice chemistry. ISO and ground-based results have confirmed that the most abundant ice species in warm regions close to massive protostars are H_2O, CO_2, and CH_3OH. Ice segregation in those environments reflects the extensive thermal processing of…

Hubble Space Telescope Observations of the Broad Absorption Line QuasarPG 0946+301

Korista, Kirk T.; Arav, Nahum; de Kool, Martijn +2 more

We analyze Hubble Space Telescope (HST) and ground-based spectra of the brightest broad absorption line (BAL) quasar in the UV: PG 0946+301. A detailed study of the absorption troughs as a function of velocity is presented, facilitated by the use of a new algorithm to solve for the optical depth as a function of velocity for multiplet lines. We fi…

A Search for Companions to Nearby Brown Dwarfs: The Binary DENIS-P J1228.2-1547

Brandner, W.; Basri, G.; Martin, E. L.

Evidence for a Massive Black Hole in the S0 Galaxy NGC 4342

Cretton, Nicolas; van den Bosch, Frank C.

We present axisymmetric dynamical models of the edge-on S0 galaxy NGC 4342. This small low-luminosity galaxy harbors, in addition to its outer disk, a bright nuclear stellar disk. A combination of observations from the ground and with the Hubble Space Telescope (HST) has shown that NGC 4342 rotates rapidly and has a strong central increase in velo…

Evidence for Large-Scale Structure at z ~ 2.4 from Lyα Imaging

Keel, William C.; Windhorst, Rogier A.; Cohen, Seth H. +1 more

The history of large-scale structure depends on cosmological parameters and on how merging unfolds among both galaxies and groups. There has been recent evidence for clustering among Lyα emitters, Lyman-break galaxies, and Lyman absorbers. We present deep, wide-field medium-band imaging in redshifted Lyα of fields surrounding regions selected to h…

Near-Infrared Camera and Multi-Object Spectrometer Observations of the Hubble Deep Field: Observations, Data Reduction, and Galaxy Photometry

Schneider, Glenn; Rieke, Marcia J.; Thompson, Rodger I. +4 more

This paper presents data obtained during the NICMOS Guaranteed Time Observations of a portion of the Hubble Deep Field. The data are in a catalog format similar to the publication of the original WFPC2 Hubble Deep Field program (Williams et al.). The catalog contains 342 objects in a 49.1"x48.4" subfield of the total observed field, 235 of which a…

Barium abundances in cool dwarf stars as a constraint to s- and r-process nucleosynthesis

Bikmaev, I.; Mashonkina, L.; Gehren, T.

We revise barium abundances in 11 cool stars with metallicities ranging from -2.65 to 0.05. The results are based on differential NLTE model atmosphere analyses of spectra that have a typical S/N of 200 and a resolution of 40000 or 60000. To minimize systematic errors of theoretical modeling and to be sure that elemental surface abundances are not…