Search Publications
Star Formation History in the NICMOS Northern Hubble Deep Field
Thompson, Rodger I.; Weymann, Ray J.; Storrie-Lombardi, Lisa J.
We present the results of an extensive analysis of the star formation rates determined from the NICMOS deep images of the northern Hubble Deep Field. We use SED template fitting photometric techniques to determine both the redshift and the extinction for each galaxy in our field. Measurement of the individual extinctions provides a correction for …
A Revised Cepheid Distance to NGC 4258 and a Test of the Distance Scale
Zepf, Stephen E.; Davis, Marc; Madore, Barry F. +5 more
In a previous paper we reported a Hubble Space Telescope (HST) Cepheid distance to the galaxy NGC 4258 obtained using the calibrations and methods then standard for the Key Project. Here we reevaluate the Cepheid distance using the recently revised Key Project procedures. These revisions alter the zero points and slopes of the Cepheid period-lumin…
Morphology and Evolution of the Large Magellanic Cloud Planetary Nebulae
Mutchler, Max; Blades, J. Chris; Balick, Bruce +2 more
The LMC is ideal for studying the coevolution of planetary nebulae (PNs) and their central stars in that the debilitating uncertainties of the Galactic PN distance scale and selection biases from attenuation by interstellar dust do not apply. We present images and analyze slitless spectra that were obtained in a survey of Large Magellanic Cloud PN…
The Jet and the Supernova in GRB 990712
Christensen, L.; Hjorth, J.; Jakobsson, P. +2 more
The optical light curve of the afterglow following the gamma-ray burst GRB 990712 is reexamined. Recently published polarization measurements of that source require a collimated outflow geometry that in turn predicts a break in the light curve. We show that the V-band light curve is consistent with such a break and that the postbreak light-curve e…
The Rich Ultraviolet Spectrum of Vibrationally Excited Interstellar H2 toward HD 37903
Sofia, Ulysses J.; Meyer, David M.; Draine, B. T. +2 more
Based on recent high-resolution Hubble Space Telescope Space Telescope Imaging Spectrograph observations over the 1160-1360 Å wavelength region, we have discovered that HD 37903 (the illuminating star of the bright reflection nebula NGC 2023 in Orion) exhibits a rich spectrum of vibrationally excited interstellar H2 absorption. We have …
Observation of Polar Plumes at High Solar Altitudes
Plunkett, S. P.; Andrews, M. D.; DeForest, C. E.
Using the Large-Angle Spectrometric Coronagraph (LASCO) aboard the Solar and Heliospheric Observatory (SOHO) spacecraft, we have imaged polar plumes extending 30 Rsolar from disk center in the image plane and ~45 Rsolar in three-dimensional space, a factor of 2-3 farther than previous imaging measurements and well into the co…
Late AGB Magnetic Cycles: Magnetohydrodynamic Solutions for the Hubble Space Telescope Planetary Nebula Rings
García-Segura, Guillermo; López, José Alberto; Franco, José
The Hubble Space Telescope (HST) has revealed the existence of multiple, regularly spaced, and faint concentric shells around some planetary nebulae. Here we present two- (and a half) dimensional magnetohydrodynamic numerical simulations of the effects of a solar-like magnetic cycle, with periodic polarity inversions, in the slow wind of an asympt…
Chandra X-Ray Observatory Observation of the High-Redshift Cluster MS 1054-0321
Donahue, Megan; Garmire, Gordon P.; Canizares, Claude R. +3 more
We observed MS 1054-0321, the highest redshift cluster of galaxies in the Einstein Medium Sensitivity Survey (EMSS), with the Chandra ACIS-S detector. We find the X-ray temperature of the cluster to be 10.4+1.7-1.5 keV, lower than, but statistically consistent with, the temperature inferred previously. This temperature agrees…
The Nuclear Dynamics of M32. I. Data and Stellar Kinematics
Nelson, C.; Bender, R.; Joseph, C. L. +14 more
We have obtained optical long-slit spectroscopy of the nucleus of M32 using the Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope. The stellar rotation velocity and velocity dispersion, as well as the full line-of-sight velocity distribution (LOSVD), were determined as a function of position along the slit using two independen…
Properties of Solar Polar Coronal Hole Plasmas Observed above the Limb
Wilhelm, K.; Schühle, U.; Doschek, G. A. +2 more
We determine the line-of-sight emission measure distribution and nonthermal motions as a function of height above the limb in the north and south polar coronal holes. These quantities are derived from extreme-ultraviolet (EUV) spectra obtained from the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on the Solar and Helios…