Search Publications
Weak and Post-T Tauri Stars around B-Type Members of the Scorpius-Centaurus OB Association
Martín, E. L.
I report medium-resolution (FWHM = 1.9 Å) spectroscopic observations of six Hα emission-line stars proposed in 1993 by Meyer, Wilking, & Zinnecker to be T Tauri stars formed in the vicinity of the B1 giant sigma Sco, a bright member of the Sco-Cen OB association. Using spectroscopic criteria (spectral types, Hα and Li i equivalent widths), whi…
The Specific Globular Cluster Frequencies of Dwarf Elliptical Galaxiesfrom the Hubble Space Telescope
Ferguson, Henry C.; Stiavelli, Massimo; Whitmore, Bradley C. +2 more
The specific globular cluster frequencies (SN) for 24 dwarf elliptical (dE) galaxies in the Virgo and Fornax Clusters and the Leo Group that were imaged with the Hubble Space Telescope are presented. Combining all available data, we find that for nucleated dE (dE, N) galaxies, which are spatially distributed like giant elliptical galaxi…
Dwarf Elliptical Galaxies in the M81 Group: The Structure and Stellar Populations of BK5N and F8D1
Da Costa, G. S.; Caldwell, Nelson; Seitzer, Patrick +1 more
The M81 Group is one of the nearest groups of galaxies, but its properties are quite different from those of the Local Group. It has therefore provided a different environment for the evolution of its member galaxies. We have carried out a CCD survey of the M81 Group to search for analogs to Local Group dwarf elliptical (dE) galaxies. All the M81 …
Cosmic-Ray Modulation in the Heliosphere A Phenomenological Study
McDonald, Frank B.
The heliospheric cosmic-ray network-Pioneer 10/11, Voyager 1/2, Ulysses and IMP 8 have provided detailed observations of galactic and anomalous cosmic rays over a period of time that now exceeds 25 years and extends to heliocentric distances beyond 65 AU. These data, when compared over consecutive 11 year solar cycles, clearly establishes the exis…
Late Spectral Evolution of SN 1987A. II. Line Emission
Fransson, Claes; Kozma, Cecilia
Using the temperature and ionization calculated in our previous paper, we model the spectral evolution of SN 1987A. We find that the temperature evolution is directly reflected in the time evolution of the lines. In particular, the IR catastrophe is seen in the metal lines as a transition from thermal to nonthermal excitation, seen most clearly in…
The Ages of the Globular Clusters in the Fornax Dwarf Galaxy
Suntzeff, N. B.; Buonanno, R.; Corsi, C. E. +3 more
From observations with the Hubble Space Telescope, color-magnitude diagrams (CMDs) have been constructed for the four most metal-poor globular clusters in the Fornax dSph galaxy. These diagrams confirm that cluster 1 has a redder horizontal-branch (HB) morphology than the other three clusters despite its similarity in metallicity (the second param…
Oscillating Blue Stragglers in the Core of 47 Tucanae
Bono, Giuseppe; Gilliland, Ronald L.; Saha, Abhijit +5 more
Six SX Phe variables detected in a 39 hr time series of Hubble Space Telescope Planetary Camera exposures in the F336W (U) filter are discussed. Two of these stars show both the fundamental and first-overtone modes and are among the first double-mode SX Phe stars reported in globular clusters. One of the double-mode stars shows evidence for a thir…
HST images of a galaxy group at z=2.81, and the sizes of damped Lyalpha galaxies
Møller, P.; Warren, S. J.
We present Hubble Space Telescope (HST) WFPC2 observations in three bands (F450W=B, F467M and F814W=I) of a group of three galaxies at z=2.8 discovered in a ground-based narrow-band search for Lyalphaemission near the z=2.8 quasar PKS 0528-250. One of the galaxies is a damped Lyalpha(DLA) absorber and these observations bear on the relation betwee…
Measurement of the Abundance of Helium-3 in the Sun and in the Local Interstellar Cloud with SWICS on ULYSSES
Gloeckler, George; Geiss, Johannes
The abundance of 3He in the present day local interstellar cloud (LIC) and in the sun has important implications for the study of galactic evolution and for estimating the production of light nuclei in the early universe. Data from the Solar Wind Ion Composition Spectrometer (SWICS) on Ulysses is used to measure the isotopic ratio of helium (3He/4…
Numerical Simulations of Triggered Star Formation. I. Collapse of Dense Molecular Cloud Cores
Vanhala, Harri A. T.; Cameron, A. G. W.
Results from numerical simulations of shock waves impacting molecular cloud cores are presented. The three-dimensional smoothed particle hydrodynamics code used in the calculations includes effects from a varying adiabatic exponent, molecular, atomic, and dust cooling, as well as magnetic pseudofluid. The molecular cloud cores are assumed to be em…