Search Publications
Jet-induced Emission-Line Nebulosity and Star Formation in the High-Redshift Radio Galaxy 4C 41.17
Dey, Arjun; Dopita, Michael A.; Sutherland, Ralph S. +3 more
The high-redshift radio galaxy 4C 41.17 has been shown in earlier work to consist of a powerful radio source in which there is strong evidence for jet-induced star formation along the radio axis. We argue that nuclear photoionization is not responsible for the excitation of the emission line clouds, and we construct a jet-cloud interaction model t…
Kinematics of Metal-poor Stars in the Galaxy. II. Proper Motions for a Large Nonkinematically Selected Sample
Beers, Timothy C.; Rossi, Silvia; Platais, Imants +4 more
We present a revised catalog of 2106 Galactic stars, selected without kinematic bias and with available radial velocities, distance estimates, and metal abundances in the range -4.0<=[Fe/H]<=0.0. This update of the 1995 Beers & Sommer-Larsen catalog includes newly derived homogeneous photometric distance estimates, revised radial velocit…
Basic Principles of Solar Acoustic Holography - (Invited Review)
Braun, D. C.; Lindsey, C.
We summarize the basic principles of holographic seismic imaging of the solar interior, drawing on familiar principles in optics and parallels with standard optical holography. Computational seismic holography is accomplished by the phase-coherent wave-mechanical reconstruction of the p-mode acoustic field into the solar interior based on heliosei…
Modelling irradiance variations from the surface distribution of the solar magnetic field
Solanki, S. K.; Unruh, Y. C.; Fligge, M.
An important question in solar physics is to what extent solar surface magnetism affects the solar irradiance. Previous attempts to answer this question have employed proxies of the magnetic field to reconstruct the irradiance and compare it with observations. Here we present the first model calculations of solar irradiance variations based on var…
Exploring the brown dwarf desert with Hipparcos
Queloz, D.; Arenou, F.; Udry, S. +2 more
The orbital elements of 11 spectroscopic binaries with brown dwarf candidates (M2 sin i between 0.01 and 0.08 Msun) are combined with the Hipparcos observations in order to derive astrometric orbits. Estimations of the masses of the secondary components are thus calculated. It appears that 5 secondary masses are more than 2 s…
Identification of a Nearby Stellar Association in theHipparcos Catalog: Implications for Recent, Local Star Formation
Zuckerman, B.; Webb, R. A.
The TW Hydrae Association (~55 pc from Earth) is the nearest known region of recent star formation. Based primarily on the Hipparcos catalog, we have identified a group of nine or 10 comoving star systems at a common distance (~45 pc) from Earth that appear to comprise another, somewhat older association (``the Tucanae Association''). Together wit…
The Hubble Space Telescope Survey of BL Lacertae Objects. I. Surface Brightness Profiles, Magnitudes, and Radii of Host Galaxies
Urry, C. Megan; Scarpa, Riccardo; Treves, Aldo +2 more
We report on a large Hubble Space Telescope imaging survey of BL Lac objects, at spatial resolution >~10 times better than previous ground-based surveys. We focus on data reduction and analysis, describing the procedures used to model the host galaxy surface brightness radial profiles. A total of 69 host galaxies were resolved out of 110 object…
Models for Old, Metal-Poor Stars with Enhanced α-Element Abundances. II. Their Implications for the Ages of the Galaxy's Globular Clusters and Field Halo Stars
VandenBerg, Don A.
The ages of globular clusters (GCs) and post-turnoff field stars in the Galactic halo are derived using new stellar evolutionary models that explicitly take into account the observed abundances of the α-elements. Whereas the distances of the field subgiants considered in this study are based on Hipparcos parallax measurements, theoretical zero-age…
Resolved Spectroscopy of the Narrow-Line Region in NGC 1068: Kinematics of the Ionized Gas
Crenshaw, D. Michael; Kraemer, Steven B.
We have determined the radial velocities of the [O III]-emitting gas in the inner narrow-line region of the Seyfert 2 galaxy NGC 1068, along a slit at position angle 202 deg, from STIS observations at a spatial resolution of 0.1" and a spectral resolving power of λ/Δλ~1000. We use these data to investigate the kinematics of the narrow-line region …
2.5-11 micron spectroscopy and imaging of AGNs. Implication for unification schemes
Altieri, B.; Clavel, J.; Metcalfe, L. +6 more
We present low resolution spectrophotometric and imaging ISO observations of a sample of 57 AGNs and one non-active SB galaxy over the 2.5-11 mu m range. The sample is about equally divided into type I (<= 1.5; 28 sources) and type II (> 1.5; 29 sources) objects. The mid-IR (MIR) spectra of type I (Sf1) and type II (Sf2) objects are statisti…