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Radio Emission from Galaxies in the Hubble Deep Field
Fomalont, E. B.; Windhorst, R. A.; Richards, E. A. +2 more
We report on sensitive radio observations made with the VLA at 8.5 GHz centered on the Hubble Deep Field (HDF). We collected data in the A, CnB, C, DnC, and D configurations corresponding to angular resolutions ranging from 0.3" to 10". We detected 29 radio sources in a complete sample within 4.6‧ of the HDF center and above a flux density limit o…
The ACT Reference Catalog
Urban, S. E.; Wycoff, G. L.; Corbin, T. E.
The US Naval Observatory has completed the compilation of the ACT Reference Catalog, containing 988,758 stars covering the entire sky. The motivation behind the ACT was to provide accurate proper motions for the majority of the stars in the Tycho Catalogue. To do this, positions from new reductions of the Astrographic Catalogue (AC 2000) were comb…
The Ultraviolet Spectra of LINERs: A Comparative Study
Filippenko, Alexei V.; Ho, Luis C.; Maoz, Dan +3 more
Imaging studies have shown that ~25% of LINER galaxies display a compact nuclear UV source. As part of a program to study the nature of LINERs and their connection to the active galaxy phenomenon, we compare the Hubble Space Telescope UV (1150-3200 Å) spectra of seven such UV-bright LINERs. Data for three of the galaxies (NGC 404, 4569, and 5055) …
The Complex Kinematics of the Neutral Hydrogen Associated with I ZW 18
Salzer, John J.; Haynes, Martha P.; van Zee, Liese +1 more
We present the results of high velocity (1.3 km s^-1 channels) and high spatial (~5", or ~250 pc at the distance of I Zw 18) resolution H i synthesis observations of the blue compact dwarf galaxy I Zw 18 to investigate the link between its unique evolutionary history and the neutral gas distribution and kinematics. The H i distribution is extensiv…
Evidence for a 3 X 10^8 M_⊙ Black Hole in NGC 7052 from Hubble Space Telescope Observations of the Nuclear Gas Disk
van den Bosch, Frank C.; van der Marel, Roeland P.
We present a Hubble Space Telescope (HST) study of the nuclear region of the E4 radio galaxy NGC 7052, which has a nuclear disk of dust and gas. The Second Wide Field and Planetary Camera (WFPC2) was used to obtain B, V, and I broadband images and an Hα + [N II] narrowband image. The images yield the stellar surface brightness profile, the optical…
WFPC2 Observations of Star Clusters in the Magellanic Clouds. II. The Oldest Star Clusters in the Small Magellanic Cloud
Sarajedini, Ata; Mighell, Kenneth J.; French, Rica S.
We present our analysis of archival Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC2) observations in F450W (~B) and F555W (~V) of the intermediate-age populous star clusters NGC 121, NGC 339, NGC 361, NGC 416, and Kron 3 in the Small Magellanic Cloud. We use published photometry of two other SMC populous star clusters, Lindsay 1 and Li…
Wide Field Planetary Camera 2 Observations of Leo A: A Predominantly Young Galaxy within the Local Group
Saha, A.; Gallagher, J. S.; Cole, A. A. +6 more
The unprecedented detail of the Wide Field Planetary Camera 2 (WFPC2) color-magnitude diagrams (CMDs) of the resolved stellar population of Leo A presented here allows us to determine a new distance and an accurate star formation history for this extremely metal-poor Local Group dwarf irregular galaxy. From the position of the red clump, the heliu…
FLIERs and Other Microstructures in Planetary Nebulae. IV. Images of Elliptical PNs from the Hubble Space Telescope
Perinotto, Mario; Balick, Bruce; Hajian, Arsen R. +3 more
We report new results from high spatial resolution Wide Field Planetary Camera 2 imaging studies of ``FLIERs'' and other microstructures in the planetary nebulae NGC 3242, 6826, 7009, and 7662. Most FLIERs have head-tail morphologies, with the tails pointing outward from the nucleus. Ionization gradients that decrease with distance from the nebula…
Wide Field Planetary Camera 2 Imaging of the Globular Cluster System of the S0 Galaxy NGC 3115
Kundu, Arunav; Whitmore, Bradley C.
Using the Wide Field Planetary Camera 2 on board the Hubble Space Telescope we have identified 144 globular cluster candidates in the inner region of the S0 galaxy NGC 3115. The color distribution of the globular clusters is bimodal, with a blue peak at V-I = 0.96 mag and a red peak at V-I = 1.17 mag. There are roughly equal number of blue and red…
HIPPARCOS Subdwarf Parallaxes: Metal-rich Clusters and the Thick Disk
Reid, Neill
We have used main-sequence fitting to calibrate the distances to the globular clusters NGC 6397, M5, NGC 288, M71, and 47 Tucanae, matching the cluster photometry against data for subdwarfs with precise Hipparcos parallax measurements and accurate abundance determinations. Both the cluster and subdwarf abundance scales are tied to high-resolution …