Search Publications
The ACS Survey of Galactic Globular Clusters. I. Overview and Clusters without Previous Hubble Space Telescope Photometry
Anderson, Jay; Dotter, Aaron; Sarajedini, Ata +10 more
We present the first results of a large Advanced Camera for Surveys (ACS) survey of Galactic globular clusters. This Hubble Space Telescope (HST) Treasury project is designed to obtain photometry with S/N (signal-to-noise ratio) gtrsim10 for main-sequence stars with masses gtrsim0.2 Modot in a sample of globulars using the ACS Wide Fiel…
Hubble Space Telescope Fine Guidance Sensor Parallaxes of Galactic Cepheid Variable Stars: Period-Luminosity Relations
Freedman, Wendy L.; Harrison, Thomas E.; Bean, Jacob L. +6 more
We present new absolute trigonometric parallaxes and relative proper motions for nine Galactic Cepheid variable stars: ell Car, ζ Gem, β Dor, W Sgr, X Sgr, Y Sgr, FF Aql, T Vul, and RT Aur. We obtain these results with astrometric data from Fine Guidance Sensor 1r, a white-light interferometer on the Hubble Space Telescope. We find absolute parall…
The ACS Survey of Galactic Globular Clusters. II. Stellar Evolution Tracks, Isochrones, Luminosity Functions, and Synthetic Horizontal-Branch Models
Anderson, Jay; Dotter, Aaron; Baron, E. +4 more
The ACS Survey of Galactic Globular Clusters, an HST Treasury Project, will deliver high-quality, homogeneous photometry of 65 globular clusters. This paper introduces a new collection of stellar evolution tracks and isochrones suitable for analyzing the ACS survey data. Stellar evolution models were computed at [Fe/H]=-2.5, -2.0, -1.5, -1.0, -0.5…
Preplanetary Nebulae: A Hubble Space Telescope Imaging Survey and a New Morphological Classification System
Sahai, Raghvendra; Sánchez Contreras, Carmen; Morris, Mark +1 more
Using the Hubble Space Telescope (HST), we have carried out a survey of candidate preplanetary nebulae (PPNs). We report here our discoveries of objects having well-resolved geometric structures, and we use the large sample of PPNs now imaged with HST (including previously studied objects in this class) to devise a comprehensive morphological clas…
The Hubble Flow around the Centaurus A/M83 Galaxy Complex
Dolphin, Andrew; Shaya, Edward J.; Tully, R. Brent +8 more
We present Hubble Space Telescope ACS images and color-magnitude diagrams for 24 nearby galaxies in and near the constellation of Centaurus with radial velocities VLG<550 km s-1. Distances are determined based on the luminosities of stars at the tip of the red giant branch that range from 3.0 to 6.5 Mpc. The galaxies are c…
Star Cluster Demographics. I. A General Framework and Application to the Antennae Galaxies
Whitmore, Bradley C.; Fall, S. Michael; Chandar, Rupali
We present a framework for understanding the demographics of star cluster systems and develop a toy model that incorporates a universal initial power-law mass function, selected formation histories, selected disruption laws, and a convolution with common artifacts and selection effects found in observational data. A wide variety of observations ca…
A Survey of Local Group Galaxies Currently Forming Stars. II. UBVRI Photometry of Stars in Seven Dwarfs and a Comparison of the Entire Sample
Smith, R. C.; Massey, Philip; Hodge, Paul W. +4 more
We have obtained UBVRI images with the Kitt Peak National Observatory and Cerro Tololo Inter-American Observatory 4 m telescopes and Mosaic cameras of seven dwarfs in (or near) the Local Group, all of which have known evidence of recent star formation: IC 10, NGC 6822, WLM, Sextans B, Sextans A, Pegasus, and Phoenix. We construct color-magnitude d…
Internal Properties of Ultracompact Dwarf Galaxies in the Virgo Cluster
Hilker, M.; Evstigneeva, E. A.; Drinkwater, M. J. +1 more
We present new imaging and spectroscopic observations of six ultracompact dwarf (UCD) galaxies in the Virgo Cluster, along with reanalyzed data for five Fornax Cluster UCDs. These are the most luminous UCDs: -14 mag < MV < -12 mag. Our Hubble Space Telescope imaging shows that most of the UCDs have shallow or steep cusps in their …
Structural Parameters for Globular Clusters in M31 and Generalizations for the Fundamental Plane
Forbes, Duncan A.; Barmby, Pauline; Harris, William E. +2 more
The structures of globular clusters (GCs) reflect their dynamical states and past histories. High-resolution imaging allows the exploration of morphologies of clusters in other galaxies. Surface brightness profiles from new Hubble Space Telescope observations of 34 GCs in M31 are presented, together with fits of several different structural models…
Visual Binaries in the Orion Nebula Cluster
Bally, John; Reipurth, Bo; Connelley, Michael S. +1 more
We have carried out a major survey for visual binaries toward the Orion Nebula Cluster, using images obtained with the Advanced Camera for Surveys on the Hubble Space Telescope through an Hα filter. From 1051 stars more than 60″ from θ1 Ori C, we have selected 781 that fulfill the criteria for membership in the Orion Nebula Cluster. Amo…