Search Publications
The Hubble Space Telescope Key Project on the Extragalactic Distance Scale. XXVIII. Combining the Constraints on the Hubble Constant
Kelson, Daniel D.; Illingworth, Garth D.; Huchra, John P. +14 more
Since the launch of Hubble Space Telescope (HST) 9 yr ago, Cepheid distances to 25 galaxies have been determined for the purpose of calibrating secondary distance indicators. Eighteen of these have been measured by the HST Key Project team, six by the Supernova Calibration Project, and one independently by Tanvir. Collectively, this work sets out …
On the Nature of Soft X-Ray Weak Quasi-stellar Objects
Brandt, W. N.; Laor, A.; Wills, Beverley J.
Recent studies of quasi-stellar objects (QSOs) with ROSAT suggest the existence of a significant population of soft X-ray weak QSOs (SXW QSOs) where the soft X-ray flux is ~10-30 times smaller than in typical QSOs. Why are these QSOs soft X-ray weak, and what is their relationship to broad absorption line QSOs (BAL QSOs) and X-ray warm absorber QS…
The Evolution of the Galactic Morphological Types in Clusters
Couch, Warrick J.; Poggianti, Bianca M.; Fasano, Giovanni +3 more
The morphological types of galaxies in nine clusters in the redshift range 0.1<~z<~0.25 are derived from very good seeing images taken at the NOT and the La Silla-Danish telescopes, with all galaxies at MV<-20 and within the central ~1 Mpc2 area being classified. With the purpose of investigating the evolution of the…
Hubble Space Telescope Photometry and Keck Spectroscopy of the Rich Cluster MS 1054-03: Morphologies, Butcher-Oemler Effect, and the Color-Magnitude Relation at Z = 0.83
van Dokkum, Pieter G.; Franx, Marijn; Kelson, Daniel D. +2 more
We present a study of 81 I-band selected, spectroscopically confirmed members of the X-ray cluster MS 1054-03 at z=0.83. Redshifts and spectral types were determined from Keck spectroscopy. Morphologies and accurate colors were determined from a large mosaic of HST WFPC2 images in RF606W and IF814W, corresponding to U and B i…
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<…
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…
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…