Search Publications
The Multitude of Molecular Hydrogen Knots in the Helix Nebula
McCullough, Peter; Meixner, Margaret; Speck, Angela +2 more
We present Hubble Space Telescope NICMOS imaging of the H2 2.12 µm emission in five fields in the Helix Nebula ranging in radial distance from 250" to 450" from the central star. The images reveal arcuate structures with their apexes pointing toward the central star. These molecular hydrogen knots are most highly structured in the…
SDSS J024634.11-082536.2: A New Gravitationally Lensed Quasar from the Sloan Digital Sky Survey
Castander, Francisco J.; White, Richard L.; Hall, Patrick B. +14 more
We report the discovery of a new two-image gravitationally lensed quasar, SDSS J024634.11-082536.2 (SDSS J0246-0825). This object was selected as a lensed quasar candidate from the Sloan Digital Sky Survey (SDSS) by the same algorithm that was used to discover other SDSS lensed quasars (e.g., SDSS J0924+0219). Multicolor imaging with the Magellan …
A Multi-Instrument Study of the Helix Nebula Knots with the Hubble Space Telescope
O'Dell, C. R.; Henney, W. J.; Ferland, G. J.
We have conducted a combined observational and theoretical investigation of the ubiquitous knots in the Helix Nebula (NGC 7293). We have constructed a combined hydrodynamic + radiation model for the ionized portion of these knots and have accurately calculated a static model for their molecular regions. Imaging observations in optical emission lin…
A Deep Radio Survey of Abell 2125. II. Accelerated Galaxy Evolution during a Cluster-Cluster Merger
Morrison, G. E.; Wang, Q. D.; Owen, Frazer N. +2 more
Using our extensive radio, optical, near-IR, and X-ray imaging and spectroscopy, we consider the reason for the unusually large number of radio-detected galaxies, mostly found outside the cluster core, in Abell 2125 (z=0.2465, richness class 4). With 20 cm VLA data, we detect continuum emission from 90 cluster members. The multiwavelength properti…
Hubble Space Telescope NICMOS Imaging Polarimetry of Proto-Planetary Nebulae: Probing the Dust Shell Structure via Polarized Light
Ueta, Toshiya; Meixner, Margaret; Murakawa, Koji
Using NICMOS on the Hubble Space Telescope, we have performed imaging polarimetry of proto-planetary nebulae (PPNs). Our objective is to study the structure of optically thin circumstellar shells of post-asymptotic giant branch (AGB) stars by separating dust-scattered, linearly polarized starlight from unpolarized direct starlight. This unique tec…
High-Mass Triple Systems: The Classical Cepheid Y Carinae
Evans, Nancy Remage; Carpenter, Kenneth G.; Robinson, Richard +2 more
We have obtained a Hubble Space Telescope STIS ultraviolet high-dispersion echelle-mode spectrum of the binary companion of the double-mode classical Cepheid Y Car. The velocity measured for the hot companion from this spectrum is very different from reasonable predictions for binary motion, implying that the companion is itself a short-period bin…
Hubble Space Telescope Advanced Camera for Surveys Observations of the z = 6.42 Quasar SDSS J1148+5251: A Leak in the Gunn-Peterson Trough
White, Richard L.; Strauss, Michael A.; Fan, Xiaohui +1 more
The Hubble Space Telescope Advanced Camera for Surveys has been used to obtain a narrowband image of the weak emission peak seen at λ=7205 Å in the Gunn-Peterson Lyβ absorption trough of the highest redshift quasar, SDSS J1148+5251. The emission looks perfectly pointlike; there is no evidence for the intervening galaxy that we previously suggested…
Jet-Gas Interaction in Markarian 78. II. Ionization Mechanisms
Silverman, J. D.; Wilson, A. S.; Rosario, D. J. +2 more
We investigate the ionization mechanisms in the Seyfert galaxy Markarian 78, chosen because its narrow-line region (NLR) is dominated by a strong jet-gas interaction. Our principal aim is to ascertain whether or not shock-related ionization is important. We use Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) optical and UV…
Kinematic Structure of H2 and [Fe II] in the Bipolar Planetary Nebula M2-9
Smith, Nathan; Gehrz, Robert D.; Balick, Bruce
We present new high-dispersion, long-slit, infrared (IR) spectra of the double-shell bipolar planetary nebula M2-9 in the emission lines [Fe II] λ16435 and H2v=1-0 S(1) λ21218. H2 spectra reveal for the first time the kinematic structure of the outer shell in M2-9. Kinematics of the inner shell, traced by [Fe II], resemble th…
Hubble Space Telescope WFPC2 Photometry of the Globular Clusters M3 and M13: Binaries and Intrinsic Broadening on the Main Sequence
Bailyn, Charles D.; Zhao, Bing
We study the color-magnitude diagram (CMD) morphologies of M3 and M13 using high-precision Hubble Space Telescope photometry. Asymmetric broadening above and to the red of the main sequence is apparent. We use extensive artificial star experiments to synthetically reproduce chance superposition and photometric error and examine whether a main-sequ…