Search Publications
Local Group Populations With the Hubble Space Telescope. I. The M31 Globular Cluster G1=Mayall II
Freedman, Wendy L.; Rich, R. Michael; Neill, James D. +1 more
We present WFPC2 photometry of the M31 globular cluster G1 and its adjacent halo field population. The cluster is one of the most luminous in the Local Group (~10^6^ L_sun_) and is at a projected distance of 39.5 kpc from the nucleus near the major axis of M31. The color of the red giant branch is similar to that of 47 Tuc, confirming previous gro…
Detection of a LY alpha Emission-Line Companion to the z=4.69 Quasar BR 1202$-0725
McMahon, Richard G.; Egami, Eiichi; Hu, Esther M.
We report the detection of a nearby emission-line companion to the z = 4.695 quasar BR 1202-0725. Deep narrowband exposures on this field from the University of Hawaii 2.2 m telescope show a Ly alpha flux of 1.5 x 10-16 ergs cm-2 s-1. High-resolution imaging in the F814W filter band with the Hubble Space Telescope Wide Field Planetary Camera (WFPC…
Ultraviolet Extinction by Interstellar Dust in External Galaxies: M31
Massey, Philip; Clayton, Geoffrey C.; Hutchings, J. B. +2 more
Hubble Space Telescope (HST) Faint Object Spectrograph (FOS) spectra of stars in OB associations of M31 are used to derive the UV extinction by interstellar dust in M31 by three different methods: (1) comparing spectra of M31 star pairs, (2) comparing spectra of M31 stars to those of Galactic standard stars, and (3) comparing M31 star spectra to a…
The average X-ray/gamma-ray spectrum of radio-quiet Seyfert 1s
Zdziarski, Andrzej A.; George, Ian M.; Gondek, Dorota +5 more
We have obtained the average 1-500 keV spectrum of radio-quiet Seyfert 1s using data from EXOSAT, Ginga, HEAO-1 and GRO OSSE. The spectral fit to the combined average EXOSAT and OSSE data is fully consistent with that for Ginga and OSSE, confirming results from an earlier Ginga/OSSE sample. The average spectrum is well fitted by a power-law X-ray …
The Cosmological Density and Ionization of Hot Gas: O VI Absorption in Quasar Spectra
Burles, Scott; Tytler, David
We have conducted the first survey for O VI 1032, 1038 A absorption lines in QSO spectra. We used medium-resolution (R ~ 1300) high signal- to-noise (~20) Faint Object Spectrograph spectra of 11 QSOs (0.53 <= z_em_ <= 2.07) from the Hubble Space Telescope archive. We use simulated spectra to determine the significance of the line identificat…
Interaction of a nonuniform solar wind with the local interstellar medium
Zank, G. P.; Pauls, H. L.
Results from a fully time dependent three-dimensional gasdynamic model of the interaction of the solar wind with the local interstellar medium are presented. Both subsonic and supersonic interstellar winds are considered, while the mediating effects of interstellar neutrals, magnetic fields, and cosmic rays are ignored. In accord with solar minimu…
K Giants in 47 Tucanae: Detection of a New Class of Variable Stars
Gilliland, Ronald L.; Edmonds, Peter D.
We report the discovery of variability among K giants in the globular cluster 47 Tucanae, using a time series of U exposures with the Hubble Space Telescope. The variables lie along a narrow band in the color-magnitude diagram, joining the faint end of the asymptotic giant branch to the red giant branch. The variations, if coherent, mostly have pe…
Thermal H_2_O emission from the Herbig-Haro flow HH 54.
Liseau, R.; White, G. J.; Church, S. +29 more
The first detection of thermal water emission from a Herbig-Haro object is presented. The observations were performed with the Lws (Long Wavelength Spectrograph) aboard Iso (Infrared Space Observatory). Besides H_2_O, rotational lines of CO are present in the spectrum of HH 54. These high-J CO lines are used to derive the physical model parameters…
First results of ISO-SWS observations of Jupiter.
Beintema, D. A.; Lellouch, E.; Encrenaz, T. +17 more
The spectrum of Jupiter has been recorded between 2.75 and 14.5µm with the grating mode of the Short-Wavelength Spectrometer (SWS) of ISO. The resolving power is 1500. The main preliminary results of this observation are (1) at 3µm, the first spectroscopic signature, probably associated with NH_3_ ice, of the Jovian cloud at 0.5 bar an…
Hubble Space Telescope Observations of the Double Nucleus of NGC 4486B
Gebhardt, Karl; Richstone, Douglas; Kormendy, John +7 more
Hubble Space Telescope WFPC2 images show that the low-luminosity elliptical galaxy companion to M87, NGC 4486B, has a double nucleus that resembles the one discovered in M31. The NGC 4486B nucleus comprises two peaks separated by ~0."15 or 12 pc. Neither peak is coincident with the galaxy photocenter, which falls between them. The nuclear morpholo…