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WIYN Open Cluster Study. VII. NGC 2451A and the Hipparcos Distance Scale
Deliyannis, Constantine P.; Kozhurina-Platais, Vera; Girard, Terrence M. +5 more
We provide new evidence that NGC 2451A is undoubtedly a young open cluster, although sparsely populated. New cluster membership has been derived from relative proper motions of 5868 stars. In total, 136 stars down to V~15 have membership probability Pµ>=2%. New CCD BV photometry indicates that about 70 stars are indeed main-seq…
Compact Star Clusters in M81. II. Two Populations
Chandar, Rupali; Ford, Holland C.; Tsvetanov, Zlatan
We present the color and magnitude distributions of compact star clusters discovered in the early-type spiral galaxy M81, from Hubble Space Telescope Wide Field Planetary Camera 2 B, V, and I-band imaging. These clearly show the presence of two cluster populations-a typical red globular cluster system, as well as a young population, which was not …
Molecular Gas and Star Formation in NGC 3077
Meier, David S.; Turner, Jean L.; Beck, Sara C.
We present high-resolution (~2.5") CO(1-0) and CO(2-1) images of the central 1 kpc of NGC 3077 made with the Owens Valley Millimeter Array. CO emission is distributed in three major complexes, which resolve into at least seven giant molecular clouds (GMCs). Two complexes are associated with the central starburst. A third, more distant complex is n…
Diameters of δ Cephei and η Aquilae Measured with the Navy Prototype Optical Interferometer
Hajian, Arsen R.; Hummel, C. A.; Germain, M. E. +5 more
We have measured the diameters of the Cepheid variables δ Cephei (18 nights) and η Aquilae (11 nights) with the Navy Prototype Optical Interferometer. The primary results of these observations are the mean angular diameters <θLD> of these Cepheids: 1.520+/-0.014 milliseconds of arc (mas) for δ Cep and 1.69+/-0.04 mas for η Aql. We…
Ultraviolet Signposts of Resonant Dynamics in the Starburst-ringed SAB Galaxy M94 (NGC 4736)
Madore, Barry F.; Keel, William C.; O'Connell, Robert W. +10 more
The dynamic orchestration of star-birth activity in the starburst-ringed galaxy M94 (NGC 4736) is investigated using images from the Ultraviolet Imaging Telescope (UIT; far-ultraviolet [FUV] band), Hubble Space Telescope (HST; near-ultraviolet [NUV] band), Kitt Peak 0.9 m telescope (Hα, R, and I bands), and Palomar 5 m telescope (B band), along wi…
The Continuing Slow Decline of AG Pegasi
Kenyon, Scott J.; Proga, Daniel; Keyes, Charles D.
We analyze optical and ultraviolet observations of the symbiotic binary AG Pegasi acquired during 1992-1997. The bolometric luminosity of the hot component declined by a factor of 2-3 from 1980-1985 to 1997. Since 1992, the effective temperature of the hot component may have declined by 10%-20%, but this decline is comparable to the measurement er…
Abundances in the Planetary Nebula IC 5217
Feibelman, Walter A.; Hyung, Siek; Aller, Lawrence H. +1 more
High-resolution optical wavelength spectroscopic data were secured in the optical wavelengths, 3700-10050 Å, for the planetary nebula IC 5217 with the Hamilton Echelle Spectrograph at Lick Observatory. These optical spectra have been analyzed along with the near-UV and UV archive data. Diagnostic analyses indicate a nebular physical condition with…
The New Two-Image Gravitational Lens System CLASS B2319+051
Pearson, T. J.; Blandford, R. D.; Koopmans, L. V. E. +10 more
We report the discovery of a new two-image gravitational lens system, CLASS B2319+051, from the Cosmic Lens All-Sky Survey. Radio imaging with the Very Large Array (VLA) and Multielement Radio-linked Interferometer Network (MERLIN) shows two compact components with a flux density ratio of ~=5:1, separated by 1.36". Observations with the Very Long …
The Evolution of Galaxy Morphology for Galaxies in the Canada-France Redshift Survey
van den Bergh, Sidney
The images of 229 galaxies in the Canada-France Redshift Survey have been classified on the DDO system. These observations were combined with previous classifications of galaxies with known redshifts in the Hubble Deep Field. The combined sample provides homogeneous morphological classifications for 425 galaxies of known redshift. The fraction of …
Hubble Space Telescope NICMOS Imaging of the Cores of M31 and M32
Rieke, Marcia J.; Corbin, Michael R.; O'Neil, Earl
We present 1.1, 1.6, and 2.2 µm images of the cores of the Local Group galaxies M31 and M32 obtained with the Near Infrared Camera and Multi-Object Spectrometer of the Hubble Space Telescope (HST). These images are also compared with optical images of the galaxies obtained with the HST Wide Field Planetary Camera 2 (WFPC2). In M31, the nucle…