Search Publications
Automated Morphological Classification in Deep Hubble Space Telescope UBVI Fields: Rapidly and Passively Evolving Faint Galaxy Populations
Keel, William C.; Driver, Simon P.; Windhorst, Rogier A. +1 more
We analyze deep Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC2) images in U, B, V, I using artificial neural network (ANN) classifiers, which are based on galaxy surface brightness and light profile (but not on color nor on scale length, rhl). The ANN distinguishes quite well between E/S0, Sabc, and Sd/Irr+M galaxies (M for merging sy…
ISOCAM observations of the Antennae Galaxies.
Altieri, B.; Cesarsky, C.; Boulanger, F. +10 more
We have mapped the Antennae Galaxies (NGC4038/39) in the 6.7 and 15µm continuum emission using ISOCAM (Cesarsky et al., 1996A&A...315L..32C) with =~5 - 8" resolution. Spectrophotometric observations with the CVF in the spectral range 5.5 to 16.5µm have also been obtained. We compare the distribution of the infrared emission in the …
The Discovery of Young, Luminous, Compact Stellar Clusters in the Starburst Galaxy NGC 253
Watson, A. M.; Holtzman, J. A.; Stapelfeldt, K. R. +14 more
We report the discovery of four young, luminous, compact stellar clusters in the central region of the starburst spiral galaxy NGC 253. One cluster has an intrinsic M_V_ of about -15 or brighter, an inferred mass in excess of 1.5 x 10^6^ M_sun_, assuming a Salpeter IMF from 0.08 M_sun_ to 100 M_sun_, and is resolved with a half-light radius of abo…
Solid methane toward deeply embedded protostars.
Prusti, T.; de Graauw, T.; Whittet, D. C. B. +6 more
We report on the detection of an absorption feature near 7.67µ m toward the deeply embedded protostellar objects W 33A and NGC 7538 : IRS9. Comparison with laboratory spectra shows that this feature can be identified as the ν_4_ (`deformation') mode of solid state CH_4_ embedded in polar molecules (i.e., H_2_O and/or CH_3_OH) in icy grain ma…
SWS observations of IR emission features towards compact HII regions.
Heras, A. M.; Kessler, M. F.; de Graauw, T. +17 more
We present ISO Short Wavelength Spectrometer (SWS) grating spectra of six compact HII regions. In addition to strong emission lines from atomic species these spectra display infrared bands attributed to Polycyclic Aromatic Hydrocarbons (PAHs). The continuous spectral coverage of the present observations and the high spectral resolution allow to de…
The heliospheric magnetic field at solar minimum: ULYSSES observations from pole to pole.
Balogh, A.; Horbury, T. S.; Forsyth, R. J. +3 more
The fast transit of the Ulysses spacecraft from the south polar regions of the heliosphere to the north polar regions has allowed us to obtain a unique perspective on the configuration and properties of the heliospheric magnetic field at a time of solar minimum activity. We compare the magnetic field in the northern and southern hemispheres and fi…
The β Pictoris phenomenon among Herbig Ae/Be stars. UV and optical high dispersion spectra.
Talavera, A.; McCollum, B.; Sitko, M. L. +10 more
We present a survey of high dispersion UV and optical spectra of Herbig Ae/Be (HAeBe) and related stars. We find accreting, circumstellar gas over the velocity range +100 to +400km/s, and absorption profiles similar to those seen toward β Pic, in 36% of the 33 HAeBe stars with IUE data as well as in 3 non-emission B stars. We also find evidence of…
Interstellar Gas-Phase Abundances and Physical Conditions toward Two Distant High-Latitude Halo Stars
Sembach, Kenneth R.; Savage, Blair D.
Rapid energy dissipation and variability of the lo-Jupiter electrodynamic circuit
Prangé, Renée; Rego, Daniel; Ip, Wing +3 more
THE electrodynamic interaction between Jupiter and the closest of its large moons, Io, is unique in the Solar system. Io's volcanoes eject a considerable amount of material into the inner jovian system (>1 tonne per second), much of it in the form of ions1; the motion of Io through Jupiter's powerful magnetic field in turn generates …
A large polar crown coronal mass ejection and a ``problem'' geomagnetic storm: April 14-23, 1994
Dryer, M.; Weiss, L.; Singer, H. +2 more
In the 1960s and 1970s, systematic programs to associate geomagnetic storms with solar flares gave rise to a category of ``problem storms'' for which there were no clear associations or for which the associations were with solar activity that seemed too insignificant to properly account for the magnitude of the geomagnetic events. In the last 2 de…