Search Publications
Proper Motions of Dwarf Spheroidal Galaxies from Hubble Space Telescope Imaging. II. Measurement for Carina
Minniti, Dante; Mateo, Mario; Piatek, Slawomir +4 more
This article presents and discusses a measurement of the proper motion for the Carina dwarf spheroidal galaxy (dSph) from images in two distinct fields in the direction of Carina taken with the Hubble Space Telescope, at three epochs. Each field contains a confirmed quasi-stellar object that is the reference point for measuring the proper motion o…
Observational Constraints on Disk Heating as a Function of Hubble Type
Shapiro, Kristen L.; Gerssen, Joris; van der Marel, Roeland P.
Current understanding of the secular evolution of galactic disks suggests that this process is dominated by two or more ``heating'' mechanisms, which increase the random motions of stars in the disk. In particular, the gravitational influence of giant molecular clouds and irregularities in the spiral potential have been proposed to explain the obs…
Hubble Space Telescope Detection of Spiral Structure in Two Coma Cluster Dwarf Galaxies
Jerjen, Helmut; Graham, Alister W.; Guzmán, Rafael
We report the discovery of spiral-like structure in Hubble Space Telescope images of two dwarf galaxies (GMP 3292 and GMP 3629) belonging to the Coma Cluster. GMP 3629 is the faintest such galaxy detected in a cluster environment, and it is the first such galaxy observed in the dense Coma Cluster. The large bulge and the faintness of the broad spi…
Radial Velocity Studies of Close Binary Stars. VIII.
Rucinski, Slavek M.; Capobianco, Christopher C.; Lu, Wenxian +7 more
Radial velocity measurements and sine-curve fits to the orbital velocity variations are presented for the seventh set of 10 close binary systems: V410 Aur, V523 Cas, QW Gem, V921 Her, V2357 Oph, V1130 Tau, HN UMa, HX UMa, HD 93917, and NSV 223. All systems but three (V523 Cas, HD 93917, NSV 223) were discovered photometrically by the Hipparcos mis…
Hubble Space Telescope Astrometry of m4 and the Galactic Constant V0/R0
Anderson, Jay; Bedin, Luigi R.; Piotto, Giampaolo +1 more
From multiepoch WFPC2/HST observations we present astrometric measurements of stars in the Galactic globular cluster M4 (NGC 6121) and in the foreground and background. The presence of an extragalactic point source allows us to determine the absolute proper motion of the cluster and, through use of the field stars in this region only 18° from the …
Deep Hubble Space Telescope Imaging of Sextans A. III. The Star Formation History
Dolphin, Andrew E.; Skillman, Evan D.; Saha, A. +6 more
We present a measurement of the star formation history of Sextans A, based on WFPC2 photometry that is 50% complete to V=27.5 (MV~+1.9) and I=27.0. The star formation history and chemical enrichment history have been measured through modeling of the color-magnitude diagram (CMD). We find evidence for increased reddening in the youngest …
Chandra and XMM-Newton Observations of the First Quasars: X-Rays from the Age of Cosmic Enlightenment
Brandt, W. N.; Strauss, Michael A.; Vignali, C. +6 more
We report on Chandra and XMM-Newton observations of a sample of 13 quasars at z~4.7-5.4 mostly taken from the Sloan Digital Sky Survey (SDSS). The present sample complements previous X-ray studies of z>=4 quasars, in which the majority of the objects are optically more luminous and at lower redshifts. All but two of our quasars have been detect…
The Araucaria Project: Dependence of Mean K, J, and I Absolute Magnitudes of Red Clump Stars on Metallicity and Age
Udalski, A.; Gieren, W.; Pietrzyński, G.
As a part of our ongoing Araucaria Project on the improvement of stellar distance indicators we present deep near-infrared JK imaging of several fields in four Local Group galaxies: LMC, SMC, and the Carina and Fornax dwarf galaxies. These data were obtained under excellent seeing conditions at the European Southern Observatory Very Large Telescop…
From Globular Clusters to Tidal Dwarfs: Structure Formation in the Tidal Tails of Merging Galaxies
Charlton, Jane C.; Kundu, Arunav; Gallagher, Sarah C. +5 more
Using V and I images obtained with the Wide Field Planetary Camera 2 (WFPC2) of the Hubble Space Telescope, we investigate compact stellar structures within tidal tails. Six regions of tidal debris in the four classic ``Toomre sequence'' mergers: NGC 4038/39 (``Antennae''), NGC 3256, NGC 3921, and NGC 7252 (``Atoms for Peace'') have been studied i…
WIYN Open Cluster Study. XVII. Astrometry and Membership to V=21 in NGC 188
Kozhurina-Platais, Vera; Girard, Terrence M.; van Altena, William F. +2 more
We present techniques for obtaining precision astrometry using old photographic plates from assorted large-aperture reflectors in combination with recent CCD Mosaic Imager frames. At the core of this approach is a transformation of plate/CCD coordinates into a previously constructed astrometric reference frame around the open cluster NGC 188. This…