Search Publications
Structure and Mass of a Young Globular Cluster in NGC 6946
Brodie, Jean P.; Elmegreen, Bruce G.; Hodge, Paul W. +3 more
Using the Wide Field Planetary Camera 2 on board the Hubble Space Telescope, we have imaged a luminous young star cluster in the nearby spiral galaxy NGC 6946. Within a radius of 65 pc, the cluster has an absolute visual magnitude, MV=-13.2, comparable to the most luminous young ``super star clusters'' in the Antennae merger galaxy. UBV…
Hubble Space Telescope Optical-Near-Infrared Colors of Nearby R1/4 and Exponential Bulges
Stiavelli, Massimo; de Zeeuw, P. Tim; Carollo, C. Marcella +2 more
We have analyzed V, H, and J Hubble Space Telescope (HST) images for a sample of early- to late-type spiral galaxies and have reported elsewhere the statistical frequency of R1/4-law and exponential bulges in our sample as a function of Hubble type and the frequency of occurrence and structural properties of the resolved central nuclei …
Unusual Depletions toward the SMC Star SK 155-Differences in Dust Composition in the SMC Interstellar Medium?
York, Donald G.; Blades, J. Chris; Welty, Daniel E. +2 more
We report initial results from an analysis of Hubble Space Telescope/Space Telescope Imaging Spectrograph echelle spectra of interstellar absorption toward Sk 155, located in the ``wing'' region of the SMC. There are at least 12 Milky Way (disk and halo) and at least 25 SMC components discernible in the profiles of various neutral and singly ioniz…
Structure of Protostellar Collapse Candidate B335 Derived from Near-Infrared Extinction Maps
Wilner, David J.; Myers, Philip C.; Lada, Charles J. +3 more
We present a near-infrared extinction study of the dark globule B335, a protostellar collapse candidate, using data from the Hubble Space Telescope/Near Infrared Camera and Multi-Object Spectrometer and the W. M. Keck Observatory. These data allow a new quantitative test of the ``inside-out'' collapse model previously proposed to explain molecular…
Evidence of a Supermassive Black Hole in the Galaxy NGC 1023 from the Nuclear Stellar Dynamics
Nelson, C.; Bender, R.; Green, R. F. +13 more
We analyze the nuclear stellar dynamics of the SB0 galaxy NGC 1023, utilizing observational data both from the Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope and from the ground. The stellar kinematics measured from these long-slit spectra show rapid rotation (V~70 km s-1 at a distance of 0.1"=4.9 pc from the nuc…
LBQS 0103-2753: A 0.3" Binary Quasar
Burbidge, E. M.; Junkkarinen, V.; Shields, G. A. +4 more
Imaging and spectroscopy with the Hubble Space Telescope show that LBQS 0103-2753 (V=17.8, z=0.848) is a binary quasar with a separation of 0.3", or 2.3 kpc. This is by far the smallest separation binary quasar reported to date. The two components have very different spectra, including the presence of strong broad absorption lines (BALs) in compon…
Tailored Analyses of the WN 8 Stars WR 40 and WR 16
Hillier, D. J.; Herald, J. E.; Schulte-Ladbeck, R. E.
We present the results of tailored spectral analyses of two WN 8 Wolf-Rayet stars: WR 40 (HD 96548) and WR 16 (HD 86161). These analyses were carried out utilizing line-blanketed non-LTE model atmospheres with provisions for a clumped wind. For the first time in WN analyses, stellar parameters are derived by attempting to match the entire observed…
Why Are Solar Filaments More Extended in Extreme-Ultraviolet Lines than in Hα?
Heinzel, P.; Schmieder, B.; Tziotziou, K.
A long solar filament was observed simultaneously in the Hα line by THEMIS/MSDP and in selected EUV lines by the Coronal Diagnostic Spectrometer on SOHO. Co-alignment of optical and EUV images reveals that the dark EUV filament is much more extended than the Hα filament. Assuming that the EUV filament represents Lyman continuum absorption of the b…
Imaging an Emerging Active Region with Helioseismic Tomography
Christensen-Dalsgaard, Jørgen; Duvall, Thomas L., Jr.; Jensen, Jesper Munk +1 more
The wave-speed structure beneath an emerging active region is derived from helioseismic time-distance data using inversion techniques developed in geophysics. We use Fresnel zone-based sensitivity kernels along with a Fourier domain-based regularized least-squares inversion technique. The results show that wave-speed anomalies extend down to 20 Mm…
The Discovery of Cepheids and a New Distance to NGC 2841 Using the Hubble Space Telescope
Garnavich, P. M.; Richmond, M. W.; Stetson, P. B. +5 more
We report on the discovery of Cepheids in the spiral galaxy NGC 2841, based on observations made with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope. NGC 2841 was observed over 12 epochs using the F555W filter and over five epochs using the F814W filter. Photometry was performed using the DAOPHOT/ALLFRAME package. We discove…