Search Publications
The Metagalactic Ionizing Radiation Field at Low Redshift
Shull, J. Michael; Giroux, Mark L.; Penton, Steven V. +2 more
We compute the ionizing radiation field at low redshift, arising from Seyferts, QSOs, and starburst galaxies. This calculation combines recent Seyfert luminosity functions, extrapolated ultraviolet fluxes from our IUE-AGN database, and a new intergalactic opacity model based on Hubble Space Telescope and Keck Lyα absorber surveys. At z=0 for AGNs …
Hubble Space Telescope Observations of the CFA Seyfert 2 Galaxies: The Fueling of Active Galactic Nuclei
Pogge, Richard W.; Martini, Paul
We present an investigation of possible fueling mechanisms operating in the inner kiloparsec of Seyfert galaxies. We analyze visible and near-infrared Hubble Space Telescope images of 24 Seyfert 2 galaxies from the CfA Redshift Survey sample. In particular, we are searching for the morphological signatures of dynamical processes responsible for tr…
Evidence for Large-Scale Structure at z ~ 2.4 from Lyα Imaging
Keel, William C.; Windhorst, Rogier A.; Cohen, Seth H. +1 more
The history of large-scale structure depends on cosmological parameters and on how merging unfolds among both galaxies and groups. There has been recent evidence for clustering among Lyα emitters, Lyman-break galaxies, and Lyman absorbers. We present deep, wide-field medium-band imaging in redshifted Lyα of fields surrounding regions selected to h…
Near-Infrared Camera and Multi-Object Spectrometer Observations of the Hubble Deep Field: Observations, Data Reduction, and Galaxy Photometry
Schneider, Glenn; Rieke, Marcia J.; Thompson, Rodger I. +4 more
This paper presents data obtained during the NICMOS Guaranteed Time Observations of a portion of the Hubble Deep Field. The data are in a catalog format similar to the publication of the original WFPC2 Hubble Deep Field program (Williams et al.). The catalog contains 342 objects in a 49.1"x48.4" subfield of the total observed field, 235 of which a…
Hubble Space Telescope Photometry of the Fornax Dwarf Spheroidal Galaxy: Cluster 4 and Its Field
Castellani, M.; Marconi, G.; Buonanno, R. +3 more
Using observations from the Hubble Space Telescope archive, color-magnitude diagrams (CMDs) have been constructed for globular cluster 4 in the Fornax dwarf spheroidal galaxy and its surrounding field. These diagrams extend below the main-sequence turnoffs and have yielded measurements of the ages of the populations. The most prominent features of…
The Age, Extinction, and Distance of the Old, Metal-rich Open Cluster NGC 6791
Chaboyer, Brian; Liebert, James; Green, Elizabeth M.
An extensive grid of metal-rich isochrones utilizing the latest available input physics has been calculated for comparison with the old, metal-rich open cluster NGC 6791. The isochrones have been simultaneously fitted to BV and VI color-magnitude diagrams, with the same composition, reddening, and distance modulus required for both colors. Our bes…
Interferometric Astrometry of Proxima Centauri and Barnard's Star Using HUBBLE SPACE TELESCOPE Fine Guidance Sensor 3: Detection Limits for Substellar Companions
Hemenway, P. D.; Jefferys, W. H.; Nelan, E. +13 more
We report on a substellar-companion search utilizing interferometric fringe-tracking astrometry acquired with Fine Guidance Sensor 3 on the Hubble Space Telescope. Our targets were Proxima Centauri and Barnard's star. We obtain absolute parallax values of pi_abs=0.7687"+/-0.0003" for Proxima Cen and pi_abs=0.5454"+/-0.0003" for Barnard's star. Onc…
Star Formation Histories from Hubble Space Telescope Color-Magnitude Diagrams of Six Fields of the Large Magellanic Cloud
Olsen, Knut A. G.
We present results on the analysis of background field stars found in Hubble Space Telescope Wide Field Planetary Camera 2 observations of six of the old globular clusters of the Large Magellanic Cloud. Treated as contaminants by the globular cluster analysts, we produce (V-I,V) color-magnitude diagrams (CMDs) of the field stars and use them to ex…
Some Characteristics of Current Star Formation in the 30 Doradus Nebula Revealed by HST/NICMOS
Walborn, Nolan R.; Grebel, Eva K.; Brandner, Wolfgang +3 more
The extensive ``second generation'' of star formation within the 30 Doradus Nebula, evidently triggered by the R136 central cluster around its periphery, has been imaged with the Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) on the Hubble Space Telescope. Many new IR sources, including multiple systems, clusters, and nebular structur…
Ages for Globular Clusters in the Outer Galactic Halo: The Second-Parameter Clusters Palomar 3, Palomar 4, and Eridanus
Bond, Howard E.; Stetson, Peter B.; Richer, Harvey B. +9 more
We have used the Wide Field Planetary Camera 2 on the Hubble Space Telescope to obtain photometry of the outer halo globular clusters Palomar 3, Palomar 4, and Eridanus. These three are classic examples of the ``second-parameter'' anomaly because of their red horizontal-branch morphologies in combination with their low-to-intermediate metallicitie…