Search Publications
Size and Structure of the Narrow-Line Region of Quasars
Wilson, Andrew S.; Wills, Beverley J.; Falcke, Heino +2 more
We have observed the narrow-line regions (NLRs) of the seven brightest radio-quiet Palomar-Green (or Bright Quasar Survey) quasars (z<0.5) with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope (HST). Linear-ramp filters were used to image the [O III] λ5007 line emission with 0.0455"-0.1" pixel resolution. We find that the N…
The Axisymmetric Ejecta of Supernova 1987A
Panagia, N.; Lundqvist, P.; Fransson, C. +15 more
Extensive early observations proved that the ejecta of supernova 1987A (SN 1987A) are aspherical. The most important of these early observations include (1) the ``Bochum event'' that revealed small-scale spectroscopic structure indicating chemical inhomogeneities of the ejecta, (2) spectropolarimetry that showed deviations from spherical symmetry,…
Interaction of EIT Waves with Coronal Active Regions
Thompson, B. J.; Ofman, L.
Large-scale coronal waves associated with flares were first observed by the Solar and Heliospheric Observatory (SOHO) Extreme ultraviolet Imaging Telescope (EIT). We present the first three-dimensional MHD modeling of the interaction of the EIT waves with active regions and the possibility of destabilization of an active region by these waves. The…
Discovery of a Substellar Companion to the K2 III Giant ι Draconis
Butler, R. Paul; Fischer, Debra A.; Marcy, Geoffrey W. +3 more
We report precise radial velocity measurements of the K giant ι Dra (HD 137759, HR 5744, HIP 75458), carried out at Lick Observatory, which reveal the presence of a substellar companion orbiting the primary star. A Keplerian fit to the data yields an orbital period of about 536 days and an eccentricity of 0.70. Assuming a mass of 1.05 Msolar<…
Gravitational Microlensing Events Due to Stellar-Mass Black Holes
Alcock, C.; Allsman, R. A.; Alves, D. R. +30 more
We present an analysis of the longest timescale microlensing events discovered by the MACHO Collaboration during a 7 year survey of the Galactic bulge. We find six events that exhibit very strong microlensing parallax signals due, in part, to accurate photometric data from the GMAN and MPS collaborations. The microlensing parallax fit parameters a…
Chandra Observations of ``The Antennae'' Galaxies (NGC 4038/4039). III. X-Ray Properties and Multiwavelength Associations of the X-Ray Source Population
Zezas, A.; Fabbiano, G.; Murray, S. S. +1 more
We investigate the nature of the luminous X-ray source population detected in a (72 ks) Chandra ACIS-S observation of NGC 4038/4039, the Antennae galaxies. We derive the average X-ray spectral properties of sources in different luminosity ranges, and we correlate the X-ray positions with radio, IR, and optical (Hubble Space Telescope) data. The X-…
The Evolution of Field Early-Type Galaxies to z~0.7
Stiavelli, Massimo; Treu, Tommaso; Casertano, S. +2 more
We have measured the fundamental plane (FP) parameters for a sample of 30 field early-type galaxies (E/S0s) in the redshift range 0.1<z<0.66. We find that (i) the FP is defined and tight out to the highest redshift bin; (ii) the intercept γ evolves as dγ/dz=0.58+0.09-0.13 (for Ω=0.3, ΩΛ=0.7) or, in terms of a…
Formation and Fragmentation of Gaseous Spurs in Spiral Galaxies
Kim, Woong-Tae; Ostriker, Eve C.
Intermediate-scale spurs are common in spiral galaxies, but perhaps most distinctively evident in a recent image by Scoville & Rector showing a quasi-regular series of dust lanes projecting from the arms of M51. We investigate, using time-dependent numerical MHD simulations, how such spurs could form (and subsequently fragment) from the intera…
A Revised Parallax and Its Implications for RX J185635-3754
Walter, Frederick M.; Lattimer, James M.
New astrometric analysis of four Wide Field Planetary Camera 2 images of the isolated neutron star RX J185635-3754 shows that its distance is 117+/-12 pc, nearly double the originally published distance. We argue that the star's birthplace was in the Upper Scorpius association but that a connection with ζ Ophiuchi is now unlikely. Assuming birth i…
The DEEP Groth Strip Survey. X. Number Density and Luminosity Function of Field E/S0 Galaxies at z < 1
Gebhardt, Karl; Faber, S. M.; Willmer, Christopher N. A. +7 more
We present the luminosity function and color-redshift relation of a magnitude-limited sample of 145 mostly red field E/S0 galaxies at z<~1 from the DEEP Groth Strip Survey (GSS). Using nearby galaxy images as a training set, we develop a quantitative method to classify E/S0 galaxies based on smoothness, symmetry, and bulge-to-total light ratio.…