Search Publications
Starburst-like Dust Extinction in the Small Magellanic Cloud
Gordon, Karl D.; Clayton, Geoffrey C.
The recent discovery that the ultraviolet (UV) dust extinction in starburst galaxies is similar to that found in the Small Magellanic Cloud (SMC) motivated us to reinvestigate the UV extinction found in the SMC. We have been able to improve significantly on previous studies by carefully choosing pairs of well-matched reddened and unreddened stars.…
M32 +/- 1
Lauer, Tod R.; Ajhar, Edward A.; Faber, S. M. +2 more
Multicolor HST WFPC2 images are used to study the central structure of the three Local Group galaxies M31, M32, and M33. PSF deconvolution and modeling of image aliasing are required to recover accurate brightness profiles within r < 0.5". The data present a study in contrasts that suggests different evolutionary histories. In M31, the nucleus …
Ultraviolet-Optical Observations of the Seyfert 2 Galaxies NGC 7130, NGC 5135, and IC 3639: Implications for the Starburst-Active Galactic Nucleus Connection
Heckman, Timothy; Leitherer, Claus; Wilson, Andrew S. +5 more
We present and discuss Hubble Space Telescope (HST) (WFPC2 and FOC) images and ultraviolet (GHRS) spectra plus ground-based optical spectra of three Seyfert 2 nuclei (NGC 7130, NGC 5135 and IC 3639). These galaxies, together with Mrk 477 (Heckman et al.), were selected on the basis of ultraviolet brightness from a bigger sample that comprises the …
The dark side of star formation in the Antennae galaxies
Cesarsky, C.; Duc, P. -A.; Madden, S. C. +6 more
We compare mid-infrared images of the Antennae galaxies (NGC4038/39) from the Infrared Space Observatory, with optical images from the Hubble Space Telescope. The mid-infrared observations show that the most intense starburst in this colliding system of galaxies takes place in an off-nucleus region that is inconspicuous at optical wavelengths. The…
A spectral decomposition of the variable optical, ultraviolet and X-ray continuum of NGC 5548
Zdziarski, Andrzej A.; Smith, David A.; Johnson, W. Neil +2 more
We present an analysis and decomposition of the broad-band optical/UV/X-ray/gamma-ray spectrum of the Seyfert 1 galaxy NGC 5548. The spectrum consists of an average of simultaneous optical/IUE/Ginga observations accompanied by ROSATCGRO/OSSE data from non-simultaneous observations. We show that the overall optical/UV/X-ray/gamma-ray spectrum can b…
A HST spectroscopic study of QSOs with intermediate redshift damped Lyalpha systems
Deharveng, Jean-Michel; Bergeron, Jacqueline; Le Brun, Vincent +1 more
We present HST spectra for a sample of six QSOs with intermediate redshift (z_ale 1.) damped Lyalpha systems. These observations aim at measuring the Hi column density and detect metal lines in order to investigate the metal enrichment of the gas, as well as the presence of neutral species, molecules and dust. All systems selected on the basis of …
SUMER Measurements of Nonthermal Motions: Constraints on Coronal Heating Mechanisms
Chae, Jongchul; Schühle, Udo; Lemaire, Philippe
We have determined nonthermal velocities in the quiet Sun at temperatures between 104 K and 2 × 106 K by measuring the widths of a number of EUV and far-ultraviolet (FUV) lines taken with SUMER on board the SOHO spacecraft. The broadenings owing to the SUMER instrument and the finite opacity in each line have been carefully e…
Metal-rich globular clusters in the galactic disk: new age determinations and the relation to halo clusters
Salaris, M.; Weiss, A.
New age determinations of the galactic disk globular clusters 47 Tuc, M 71 and NGC 6352 have been performed with our up-to-date alpha -enhanced stellar models. We find that all three clusters are about 9.2 Gyr old and therefore coeval with the oldest disk white dwarfs. Several arguments are presented which indicate that the initial helium content …
The Color-Magnitude Relation in CL 1358+62 at Z = 0.33: Evidence for Significant Evolution in the S0 Population
van Dokkum, Pieter G.; Franx, Marijn; Kelson, Daniel D. +3 more
We use a large, multicolor mosaic of HST WFPC2 images to measure the colors and morphologies of 194 spectroscopically confirmed members of the rich galaxy cluster CL 1358+62 at z = 0.33. We study the color-magnitude (CM) relation as a function of radius in the cluster to a limit of 4.6 arcmin from the center, equivalent to 1.6 h-15…
Externally Illuminated Young Stellar Environments in the Orion Nebula: Hubble Space Telescope Planetary Camera and Ultraviolet Observations
Johnstone, Doug; Bally, John; Sutherland, Ralph S. +1 more
We present new 0.05" resolution (22 AU) narrowband Hubble Space Telescope Planetary Camera images of externally illuminated young stellar objects embedded in the Orion Nebula. We also present 0.02" resolution (9 AU) UV images of seven externally illuminated protostellar environments and the first UV spectra that cover the spectral range between 14…