Search Publications
The Surface Brightness Fluctuation Survey of Galaxy Distances. II. Local and Large-Scale Flows
Ajhar, Edward A.; Dressler, Alan; Tonry, John L. +1 more
We present results from the Surface Brightness Fluctuation (SBF) Survey for the distances to 300 early-type galaxies, of which approximately half are ellipticals. A modest change in the zero point of the SBF relation, derived by using Cepheid distances to spirals with SBF measurements, yields a Hubble constant H0=77+/-4+/-7 km s-1<…
Large-Angle Spectrometric Coronagraph Measurements of the Energetics of Coronal Mass Ejections
Howard, R. A.; Dere, K. P.; Vourlidas, A. +1 more
We examine the energetics of coronal mass ejections (CMEs) with data from the large-angle spectrometric coronagraphs (LASCO) on SOHO. The LASCO observations provide fairly direct measurements of the mass, velocity, and dimensions of CMEs. Using these basic measurements, we determine the potential and kinetic energies and their evolution for severa…
The Hubble Space Telescope Key Project on the Extragalactic Distance Scale. XXVI. The Calibration of Population II Secondary Distance Indicators and the Value of the Hubble Constant
Kelson, Daniel D.; Illingworth, Garth D.; Madore, Barry F. +14 more
A Cepheid-based calibration is derived for four distance indicators that utilize stars in old stellar populations: the tip of the red giant branch (TRGB), the planetary nebula luminosity function (PNLF), the globular cluster luminosity function (GCLF), and the surface brightness fluctuation method (SBF). The calibration is largely based on the Cep…
The Composition and Distribution of Dust along the Line of Sight toward the Galactic Center
Lutz, D.; van Dishoeck, E. F.; Whittet, D. C. B. +5 more
We discuss the composition of dust and ice along the line of sight to the Galactic center (GC) based on analysis of mid-infrared spectra (2.4-13 µm) from the Short Wavelength Spectrometer on the Infrared Space Observatory (ISO). We have analyzed dust absorption features arising in the molecular cloud material and the diffuse interstellar med…
Intervening O VI Quasar Absorption Systems at Low Redshift: A Significant Baryon Reservoir
Tripp, Todd M.; Jenkins, Edward B.; Savage, Blair D.
Far-UV echelle spectroscopy of the radio-quiet QSO H1821+643 (zem=0.297), obtained with the Space Telescope Imaging Spectrograph (STIS) at ~7 km s-1 resolution, reveals four definite O VI absorption-line systems and one probable O VI absorber at 0.15<zabs<0.27. The four definite O VI absorbers are located nea…
The Hubble Space Telescope Survey of BL Lacertae Objects. II. Host Galaxies
Urry, C. Megan; O'Dowd, Matthew; Scarpa, Riccardo +3 more
We have used the Hubble Space Telescope (HST) WFPC2 camera to survey 132 BL Lac objects comprising seven complete radio-, X-ray-, and optically selected samples. We obtained useful images for 110 targets spanning the redshift range 0<~z<~1.3. These represent an unbiased subsample of the original 132 since they were snapshots selected to fill…
The Initial Mass Function of Low-Mass Stars and Brown Dwarfs in Young Clusters
Luhman, K. L.; Schneider, Glenn; Young, Erick T. +5 more
We have obtained images of the Trapezium Cluster (140''×140'' 0.3 pc×0.3 pc) with the Hubble Space Telescope Near-Infrared Camera and Multi-Object Spectrometer (NICMOS). Combining these data with new ground-based K-band spectra (R=800) and existing spectral types and photometry, we have constructed an H-R diagram and used it …
A Lack of Planets in 47 Tucanae from a Hubble Space Telescope Search
Edmonds, P. D.; Cochran, W. D.; Sarajedini, A. +21 more
We report results from a large Hubble Space Telescope project to observe a significant (~34,000) ensemble of main-sequence stars in the globular cluster 47 Tucanae with a goal of defining the frequency of inner orbit, gas giant planets. Simulations based on the characteristics of the 8.3 days of time series data in the F555W and F814W Wide Field P…
The Evolution of the Effective Equation of State of the Intergalactic Medium
Shull, J. Michael; Ricotti, Massimo; Gnedin, Nickolay Y.
We develop a method to extract the ``effective equation of state'' of the intergalactic medium from the Doppler (b) parameter distribution of the low-density Lyα forest. We test the method on numerical simulations and then apply it to published observations of the Lyα forest at redshifts z~=0-4. We find that the effective equation of state is clos…
The Hubble Space Telescope Key Project on the Extragalactic Distance Scale. XXIV. The Calibration of Tully-Fisher Relations and the Value of the Hubble Constant
Kelson, Daniel D.; Illingworth, Garth D.; Huchra, John P. +15 more
This paper presents the calibration of BVRIH-0.5 Tully-Fisher relations based on Cepheid distances to 21 galaxies within 25 Mpc and 23 clusters within 10,000 km s-1. These relations have been applied to several distant cluster surveys in order to derive a value for the Hubble constant, H0, mainly concentrating on a…