Search Publications
M31 Globular Clusters in the Hubble Space Telescope Archive. II. Structural Parameters
Huchra, John P.; Barmby, Pauline; Holland, Stephen
We analyze the structural parameters of the largest available sample of spatially resolved extragalactic globular clusters. The images of M31 GCs were found in a search of Hubble Space Telescope (HST) archival data, described in a companion paper. We measure the ellipticities and position angles of the clusters and conclude that the ellipticities …
Tidal dwarfs in the M81 group: The second generation?
Sarajedini, A.; Dolphin, A. E.; Grebel, E. K. +8 more
We derive quantitative star formation histories of the four suspected tidal dwarf galaxies in the M 81 group, Holmberg IX, BK3N, Arp-loop (A0952+69), and Garland, using Hubble Space Telescope/Wide Field Planetary Camera 2 images in F606W and F814W obtained as part of a Snapshot survey of dwarf galaxies in the Local Universe. We consider the spatia…
The Low End of the Initial Mass Function in Young Clusters. II. Evidence for Primordial Mass Segregation in NGC 330 in the Small Magellanic Cloud
Leitherer, Claus; Clampin, Mark; Nota, Antonella +2 more
As part of a larger program aimed at investigating the universality of the initial mass function (IMF) at low masses in a number of young clusters in the LMC and SMC, we present a new study of the low end of the stellar IMF of NGC 330, the richest young star cluster in the SMC, from deep broadband V and I images obtained with HST/WFPC2. We detect …
Characteristics of Coronal Inflows
Sheeley, N. R., Jr.; Wang, Y. -M.
This paper describes coronal inflows observed with the Large Angle Spectrometric Coronagraph (LASCO). The inflows are not seen above 5.5 Rsolar, which appears to be a ``point of no return'' for the Sun's plasmas and fields. Below this height, most inflows seem to indicate magnetic flux that is returning to the Sun after its reconnection…
Evidence for Tidal Stripping of Dark Matter Halos in Massive Cluster Lenses
Smail, Ian; Kneib, Jean-Paul; Natarajan, Priyamvada
In this Letter, we present the results of our study of galaxy-galaxy lensing in massive cluster lenses spanning z=0.17-0.58, utilizing high-quality archival Hubble Space Telescope data. Local anisotropies in the shear maps are assumed to arise from dark matter substructure within these clusters. Associating the substructure with bright early-type …
HIPPARCOS age-metallicity relation of the solar neighbourhood disc stars
Arimoto, N.; Ibukiyama, A.
We derive age-metallicity relations (AMRs) and orbital parameters for the 1658 solar neighbourhood stars to which accurate distances are measured by the HIPPARCOS satellite. The sample stars comprise 1382 thin disc stars, 229 thick disc stars, and 47 halo stars according to their orbital parameters. We find a considerable scatter for thin disc AMR…
K-Band Red Clump Distance to the Large Magellanic Cloud
Minniti, Dante; Rejkuba, Marina; Alves, David R. +1 more
The Hipparcos I-band calibration of horizontal-branch red clump giants as standard candles has lead to controversial results for the distance to the Large Magellanic Cloud (LMC). In an attempt to properly ascertain the corrections for interstellar extinction and clump age and metallicity, we analyze new multiwavelength luminosity functions of the …
Nuclear Cusps and Cores in Early-Type Galaxies as Relics of Binary Black Hole Mergers
Ravindranath, Swara; Filippenko, Alexei V.; Ho, Luis C.
We present an analysis of the central cusp slopes and core parameters of early-type galaxies using a large database of surface brightness profiles obtained from Hubble Space Telescope observations. We examine the relation between the central cusp slopes, core parameters, and black hole masses in early-type galaxies, in light of two models that att…
Observations of T Tauri Stars using Hubble Space Telescope GHRS. I. Far-Ultraviolet Emission Lines
Valenti, Jeff A.; Walter, Frederick M.; Ardila, David R. +2 more
We have analyzed Goddard High Resolution Spectrograph data of eight classical T Tauri stars (CTTSs) and one weak-lined T Tauri star (WTTS). The GHRS data consist of spectral ranges 40 Å wide centered on 1345, 1400, 1497, 1550, and 1900 Å. These UV spectra show strong Si IV and C IV emission and large quantities of sharp (~40 km s-1) H
Crossing the Yellow Void: Spatially Resolved Spectroscopy of the Post-Red Supergiant IRC +10420 and Its Circumstellar Ejecta
Smith, Nathan; Humphreys, Roberta M.; Davidson, Kris
IRC +10420 is one of the extreme hypergiant stars that define the empirical upper luminosity boundary in the H-R diagram. During their post-red supergiant evolution, these massive stars enter a temperature range (6000-9000 K) of increased dynamical instability, high mass loss, and increasing opacity, a semiforbidden region that de Jager and his co…