Search Publications
Complex C: A Low-Metallicity, High-Velocity Cloud Plunging into the Milky Way
Tripp, Todd M.; Jenkins, Edward B.; Linsky, J. L. +8 more
We present evidence that high-velocity cloud (HVC) complex C is a low-metallicity gas cloud that is plunging toward the disk and beginning to interact with the ambient gas that surrounds the Milky Way. This evidence begins with a new high-resolution (7 km s-1 FWHM) echelle spectrum of 3C 351 obtained with the Space Telescope Imaging Spe…
The Host Galaxies of Narrow-Line Seyfert 1 Galaxies: Evidence for Bar-Driven Fueling
Kraemer, S. B.; Crenshaw, D. M.; Gabel, J. R.
We present a study of the host galaxy morphologies of narrow- and broad-line Seyfert 1 galaxies (NLS1's and BLS1's) based on broadband optical images from the Hubble Space Telescope archives. We find that large-scale stellar bars, starting at ~1 kpc from the nucleus, are much more common in NLS1's than BLS1's. Furthermore, the fraction of NLS1 spi…
Parent Stars of Extrasolar Planets. VII. New Abundance Analyses of 30 Systems
Suntzeff, Nicholas B.; Gonzalez, Guillermo; Laws, Chris +4 more
The results of new spectroscopic analyses of 30 stars with giant planet and/or brown dwarf companions are presented. Values for Teff and [Fe/H] are used in conjunction with Hipparcos data and Padua isochrones to derive masses, ages, and theoretical surface gravities. These new data are combined with spectroscopic and photometric metalli…
Discovery of a Little Homunculus within the Homunculus Nebula of η Carinae
Kaiser, Mary Elizabeth; Smith, Nathan; Gull, Theodore R. +17 more
We report long-slit spectroscopic mapping of the η Carinae nebula obtained using the Space Telescope Imaging Spectrograph. The observations reveal the presence of a previously unknown bipolar emission nebula (roughly +/-2" along its major axis) embedded within the well-known and larger Homunculus Nebula. A preliminary analysis suggests that this e…
Addendum: Hubble Space Telescope Evidence for an Intermediate-Mass Black Hole in the Globular Cluster M15. II. Kinematic Analysis and Dynamical Modeling [Astron. J. 124, 3270 (2002)]
Gerssen, Joris; van der Marel, Roeland P.; Gebhardt, Karl +3 more
In Paper II, we reported the existence of a dark and compact mass component near the center of M15, based on an analysis of new data from the Hubble Space Telescope. Possible explanations for this mass component include (1) a single, intermediate-mass black hole (BH) and (2) a collection of dark remnants (e.g., neutron stars) that have sunk to the…
Spectral Energy Distributions of Seyfert Nuclei
Rieke, George H.; Alonso-Herrero, Almudena; Quillen, Alice C. +2 more
We present nuclear spectral energy distributions (SEDs) in the range 0.4-16 µm for an expanded CfA sample of Seyfert galaxies. The spectral indexes (fν~ν-αIR) from 1 to 16 µm range from αIR~0.9 to 3.8. The shapes of the spectra are correlated with Seyfert type in the sense that steeper nuclea…
Hubble Space Telescope Snapshot Study of Variable Stars in Globular Clusters: The Inner Region of NGC 6441
Rich, R. Michael; Stetson, Peter B.; Pritzl, Barton J. +4 more
We present the results of a Hubble Space Telescope snapshot program to survey the inner region of the metal-rich globular cluster NGC 6441 for its variable stars. A total of 57 variable stars were found, including 38 RR Lyrae stars, six Population II Cepheids, and 12 long-period variables. Twenty-four of the RR Lyrae stars and all of the Populatio…
STIS Spectroscopy of the Central 10 Parsecs of M81: Evidence for a Massive Black Hole
Ford, Holland; Devereux, Nick; Tsvetanov, Zlatan +1 more
Spectroscopic observations of the central 10 pc of M81 were obtained with STIS on board the Hubble Space Telescope during Cycle 7. Measurements of the Hα+[N II] blend reveal a velocity field indicative of a rotating disk of gas. The two-dimensional velocity field has been modeled as a thin disk rotating in a spherical gravitational potential. Mini…
The Rotation of the Globular Cluster 47 Tucanae in the Plane of the Sky
Anderson, Jay; King, Ivan R.
We have used the Hubble Space Telescope (HST) to measure the component of rotation of 47 Tuc in the plane of the sky, using background stars of the SMC as a reference. The rotation is comparable to that in the line of sight, showing that the axis of rotation of the cluster is considerably inclined. We also give an improved value of the absolute pr…
The Chandra Deep Field North Survey. XV. Optically Bright, X-Ray-Faint Sources
Hornschemeier, A. E.; Alexander, D. M.; Bauer, F. E. +7 more
We have analyzed optically bright, X-ray-faint [OBXF; i.e., log(fX/fR)<~-2] sources identified in an 178.9 arcmin2 area having high exposure (greater than 1500 ks) within the Chandra Deep Field North 2 Ms survey. We find 43 OBXF sources in this area, making up ~15% of the X-ray sources above a 0.5-2 keV flux of …