Search Publications
Properties of Globular Cluster Systems in Nearby Early-Type Galaxies
Forbes, Duncan A.; Brodie, Jean P.; Huchra, John P. +2 more
We present a study of globular clusters (GCs) in 17 relatively nearby early-type galaxies, based on deep F555W and F814W images from the Wide Field Planetary Camera 2, on board the Hubble Space Telescope. A detailed analysis of color distributions, cluster sizes, and luminosity functions is performed and compared with GCs in the Milky Way. In near…
New Insights from HST Studies of Globular Cluster Systems. I. Colors, Distances, and Specific Frequencies of 28 Elliptical Galaxies
Kundu, Arunav; Whitmore, Bradley C.
We present an analysis of the globular cluster systems of 28 elliptical galaxies using archival WFPC2 images in the V and I bands. The V-I color distributions of at least 50% of the galaxies appear to be bimodal at the present level of photometric accuracy. We argue that this is indicative of multiple epochs of cluster formation early in the histo…
M33: A Galaxy with No Supermassive Black Hole
Gebhardt, Karl; Richstone, Douglas; Kormendy, John +9 more
Galaxies that contain bulges appear to contain central black holes whose masses correlate with the velocity dispersion of the bulge. We show that no corresponding relationship applies in the pure disk galaxy M33. Three-integral dynamical models fit Hubble Space Telescope WFPC2 photometry and Space Telescope Imaging Spectrograph spectroscopy best i…
Population Gradients in Local Group Dwarf Spheroidal Galaxies
Grebel, Eva K.; Dolphin, Andrew; Holtzman, Jon +7 more
We present a systematic and homogeneous analysis of population gradients for the Local Group dwarf spheroidal galaxies (dSph's) Carina, Sculptor, Sextans, Tucana, and Andromeda I-III, V, and VI. For all of the Milky Way companions studied here, we find significant population gradients. The same is true for the remote dSph Tucana located at the out…
WFPC2 Images of the Central Regions of Early-Type Galaxies. I. The Data
van den Bosch, Frank C.; Rest, Armin; Ford, Holland C. +5 more
We present high-resolution R-band images of the central regions of 67 early-type galaxies obtained with the Wide Field and Planetary Camera 2 (WFPC2) aboard the Hubble Space Telescope (HST). This homogeneously selected sample roughly doubles the number of early-type galaxies that have now been imaged at HST resolution and complements similar data …
A Search for L Dwarf Binary Systems
Kirkpatrick, J. Davy; Gizis, John E.; Reid, I. Neill +1 more
We present analysis of Hubble Space Telescope (HST) planetary camera images of 20 L dwarfs identified in the course of the Two Micron All Sky Survey. Four of the targets, 2MASSW J0746425+200032, 2MASSs J0850359+105716, 2MASSW J0920122+351742, and 2MASSW J1146345+223053, have faint red companions at separations between 0.07" and 0.29" (1.6-7.6 AU).…
The Expansion Center and Dynamical Age of the Galactic Supernova Remnant Cassiopeia A
Thorstensen, John R.; van den Bergh, Sidney; Fesen, Robert A.
We present proper motions for 21 bright main shell and 17 faint, higher velocity, outer ejecta knots in the Cas A supernova remnant and use them to derive new estimates for the remnant's expansion center and age. Our study included 1951-1976 Palomar 5 m prime focus plates, 1988-1999 CCD images from the KPNO 4 m and MDM 2.4 m telescopes, and 1999 H…
High-Mass, OB Star Formation in M51: Hubble Space Telescope Hα and Paα Imaging
Scoville, N. Z.; Polletta, M.; Thompson, R. +3 more
We have obtained Hα and Paα emission-line images covering the central 3'-4' of M51 using the WFPC2 and NICMOS instruments on the Hubble Space Telescope to study the high-mass stellar population. The 0.1"-0.2" pixels provide 4.6-9 pc resolution in M51, and the Hα/Paα line ratios are used to obtain extinction estimates. A sample of 1373 Hα emission …
Central Structural Parameters of Early-Type Galaxies as Viewed with Nicmos on the Hubble Space Telescope
Ravindranath, Swara; Filippenko, Alexei V.; Ho, Luis C. +2 more
We present surface photometry for the central regions of a sample of 33 early-type (E, S0, and S0/a) galaxies observed at 1.6 µm (H band) using the Hubble Space Telescope. Dust absorption has less of an impact on the galaxy morphologies in the near-infrared than found in previous work based on observations at optical wavelengths. When presen…
Mayall II=G1 in M31: Giant Globular Cluster or Core of a Dwarf Elliptical Galaxy?
Djorgovski, S. G.; Jablonka, P.; Sarajedini, A. +3 more
Mayall II=G1 is one of the brightest globular clusters belonging to M31, the Andromeda galaxy. Our observations with the Wide Field and Planetary Camera (WFPC2) on board the Hubble Space Telescope (HST) provide photometric data for the I versus V-I and V versus V-I color-magnitude diagrams. They reach stars with magnitudes fainter than V=27 mag, w…