Search Publications
Discovery of Cepheids in IC 4182: Absolute Peak Brightness of SN IA 1937C and the Value of H 0
Panagia, N.; Saha, A.; Labhardt, Lukas +4 more
Repeated imaging of a field in the Sdm galaxy IC 4182 with the Wide Field Camera of the Hubble Space Telescope has led to the discovery of 28 Cepheid variables. The distance modulus to this galaxy, derived from the Cepheids, is (m - M) = 28.36 +/- 0.09, and the absolute magnitude at peak brightness of the Type Ia supernova SN 1937C which appeared …
The 1993 Multiwavelength Campaign on 3C 279: The Radio to Gamma-Ray Energy Distribution in Low State
Maraschi, L.; Ghisellini, G.; Pian, E. +27 more
Simultaneous observations of 3C 279 at radio, millimeter, near- infrared, optical, ultraviolet (with IUE) and X-ray (with ROSAT) wavelengths were obtained in 1992 December-1993 January, during a three week pointing at the source by the Compton Gamma Ray Observatory. The blazar was in a quiescent or "low" state during this period. Comparing the mul…
Evolution of Lyman-Limit Absorption Systems over the Redshift Range 0.40 < Z < 4.69
Irwin, M. J.; McMahon, R. G.; Storrie-Lombardi, L. J. +1 more
We present the results of a study of 15 z > 4.2 QSOs that extend statistical studies of Lyman-limit absorption line systems [N(H I) >= 1.6 x 10^17^ cm^-2^] to the highest redshifts currently possible. This data set has been combined with homogeneous data sets of low-redshift Hubble Space Telescope observations and intermediate- redshift grou…
A Spectroscopic Analysis of DAO and Hot DA White Dwarfs: The Implications of the Presence of Helium and the Nature of DAO Stars
Fontaine, G.; Bergeron, P.; Wesemael, F. +4 more
A comprehensive study of optical spectrophotometry of DAO white dwarfs is presented. A detailed analysis of the He II lambda 4686 line profiles demonstrates conclusively that the chemical composition in the atmospheres of DAO stars is not stratified, except in one object (PG 1305-017). On the other hand, line profiles calculated from models with h…
M Dwarfs, Microlensing, and the Mass Budget of the Galaxy
Gould, Andrew; Bahcall, John N.; Kirhakos, Sofia +1 more
We show that faint red stars do not contribute significantly to the mass budget of the Galaxy or to microlensing statistics. Our results are obtained by analyzing two long exposures of a high-latitude field taken with the Wide Field Camera on the newly repaired {\it Hubble Space Telescope}. Stars are easily distinguished from galaxies essentially …
HST UV Imaging of the Starburst Regions in the Wolf-Rayet Galaxy He 2-10: Newly Formed Globular Clusters?
Vacca, William D.; Conti, Peter S.
We have obtained an ultraviolet image of the Wolf-Rayet galaxy He 2-10 using the Faint Object Camera aboard the Hubble Space Telescope and a filter centered at 2200 A. From previous analysis of optical spectra of He 2-10, it is known that O-type and Wolf-Rayet stars are present in large numbers in the nuclear starburst region. In the ultraviolet r…
The X-Ray and Ultraviolet Absorbing Outflow in 3C 351
Elvis, Martin; Fiore, Fabrizio; Mathur, Smita +1 more
3C 351 (z = 0.371), an X-ray-"quiet" quasar, is one of the few quasars showing signs of a "warm absorber" in its X-ray spectrum; i.e., partially ionized absorbing material in the line of sight whose opacity depends on its ionization structure. The main feature in the X-ray spectrum is a K- edge due to O VII or O VIII. 3C 351 also shows unusually s…
Luminosity Effects and the Emission-Line Properties of Quasars with 0 < Z < 3.8
Green, Richard F.; Osmer, Patrick S.; Porter, Alain C.
We present data and a spectral atlas for 76 quasars with 2.97 < z < 3.80 and for 33 quasars with z ~ 2, together with measures of 73 quasars from the IUE archives that mostly have z < 1. The quasars provide a sampling of the luminosity-redshift plane at constant luminosity for 0 < z < 3.8, a range of a factor of 40 in luminosity for…
The Morphology of Faint Galaxies in Medium Deep Survey Images Using WFPC2
Glazebrook, K.; Illingworth, G. D.; Koo, D. C. +12 more
First results from HST Medium Deep Survey images taken with WFPC2 demonstrate that galaxy classifications can be reliably performed to magnitudes I_814_ <~ 22.0 in the F815W band. Published spectroscopic surveys to this depth indicate a mean redshift of z^bar^ ~ 0.5. We have classified over 200 galaxies in nine WFPC2 fields according to a basic…
HST/FOC Imaging of the Narrow-Line Region of NGC 1068
Boksenberg, A.; Capetti, A.; Sparks, W. B. +2 more
We present imaging observations of NGC 1068 taken with the COSTAR- corrected (Corrective-Optics Space Telescope Axial Replacement) Faint Object Camera on board the Hubble Space Telescope in the UV and optical continuum and [O III] emission lines. From these observations the structure of the nuclear region of NGC 1068 is shown to be very complex. B…