Search Publications
The Demography of Massive Dark Objects in Galaxy Centers
Gebhardt, Karl; Richstone, Douglas; Kormendy, John +9 more
We construct dynamical models for a sample of 36 nearby galaxies with Hubble Space Telescope (HST) photometry and ground-based kinematics. The models assume that each galaxy is axisymmetric, with a two-integral distribution function, arbitrary inclination angle, a position-independent stellar mass-to-light ratio Upsilon, and a central massive dark…
Evolutionary models for solar metallicity low-mass stars: mass-magnitude relationships and color-magnitude diagrams
Hauschildt, P. H.; Allard, F.; Baraffe, I. +1 more
We present evolutionary models for low mass stars from 0.075 to 1 M_sun for solar-type metallicities [M/H]= 0 and -0.5. The calculations include the most recent interior physics and the latest generation of non-grey atmosphere models. We provide mass-age-color-magnitude relationships for both metallicities. The mass-M_V and mass-M_K relations are …
Discovery of a supernova explosion at half the age of the Universe
Panagia, N.; Lidman, C.; Aldering, G. +19 more
The ultimate fate of the Universe, infinite expansion or a big crunch, can be determined by using the redshifts and distances of very distant supernovae to monitor changes in the expansion rate. We can now find large numbers of these distant supernovae, and measure their redshifts and apparent brightnesses; moreover, recent studies of nearby type …
Rotating Nuclear Rings and Extreme Starbursts in Ultraluminous Galaxies
Downes, D.; Solomon, P. M.
New CO interferometer data show that the molecular gas in infrared ultraluminous galaxies is in rotating nuclear disks or rings. The CO maps yield disk radii, kinematic major axes, rotation speeds, enclosed dynamical masses, and gas masses. The CO brightness temperatures, the double-peaked CO line profiles, the limits on thermal continuum flux fro…
Are Gamma-Ray Bursts in Star-Forming Regions?
Paczyński, Bohdan
The optical afterglow of the gamma-ray burst GRB 970508 (z=0.835) was a few hundred times more luminous than any supernova. Therefore, the name ``hypernova'' is proposed for the whole GRB/afterglow event.
There is tentative evidence that the GRBs 970228, 970508, and 970828 were close to star-forming regions. If this case is strengthened with …Supernova Limits on the Cosmic Equation of State
Filippenko, Alexei V.; Riess, Adam G.; Tonry, John +18 more
We use Type Ia supernovae studied by the High-z Supernova Search Team to constrain the properties of an energy component that may have contributed to accelerating the cosmic expansion. We find that for a flat geometry the equation-of-state parameter for the unknown component, αx = Px/ρx, must be less than -0.55 (95…
Constraints on Cosmological Models from Hubble Space Telescope Observations of High-z Supernovae
Spyromilio, J.; Diercks, A.; Schmidt, B. P. +18 more
We have coordinated Hubble Space Telescope (HST) photometry with ground-based discovery for three supernovae: Type Ia supernovae near z~0.5 (SN 1997ce, SN 1997cj) and a third event at z=0.97 (SN 1997ck). The superb spatial resolution of HST separates each supernova from its host galaxy and leads to good precision in the light curves. We use these …
The Evolution of Early-Type Galaxies in Distant Clusters
Dickinson, Mark; Eisenhardt, Peter R.; Stanford, S. A.
We present results from an optical-infrared photometric study of early-type (E+S0) galaxies in 19 galaxy clusters out to z = 0.9. The galaxy sample is selected on the basis of morphologies determined from Hubble Space Telescope (HST) WFPC2 images and is photometrically defined in the K band in order to minimize redshift-dependent selection biases.…
A Hubble Space Telescope Imaging Survey of Nearby Active Galactic Nuclei
Gorjian, Varoujan; Malkan, Matthew A.; Tam, Raymond
We have obtained WFPC2 images of 256 of the nearest (z <= 0.035) Seyfert 1, Seyfert 2, and starburst galaxies. Our 500 s broadband (F606W) exposures reveal much fine-scale structure in the centers of these galaxies, including dust lanes and patches, bars, rings, wisps, and filaments, and tidal features such as warps and tails. Most of this fine…
Star Formation in R136: A Cluster of O3 Stars Revealed by Hubble Space Telescope Spectroscopy
Massey, Philip; Hunter, Deidre A.
The R136 cluster in 30 Doradus is the prototype ``super star cluster,'' and the only example sufficiently close that its massive star content can be studied directly. We have used the Hubble Space Telescope to obtain spectra of 65 of the bluest, most luminous stars in R136 and find that the majority of these stars are of type O3, the hottest, most…