Search Publications
The Hubble Space Telescope Survey of BL Lacertae Objects. I. Surface Brightness Profiles, Magnitudes, and Radii of Host Galaxies
Urry, C. Megan; Scarpa, Riccardo; Treves, Aldo +2 more
We report on a large Hubble Space Telescope imaging survey of BL Lac objects, at spatial resolution >~10 times better than previous ground-based surveys. We focus on data reduction and analysis, describing the procedures used to model the host galaxy surface brightness radial profiles. A total of 69 host galaxies were resolved out of 110 object…
Resolved Spectroscopy of the Narrow-Line Region in NGC 1068: Kinematics of the Ionized Gas
Crenshaw, D. Michael; Kraemer, Steven B.
We have determined the radial velocities of the [O III]-emitting gas in the inner narrow-line region of the Seyfert 2 galaxy NGC 1068, along a slit at position angle 202 deg, from STIS observations at a spatial resolution of 0.1" and a spectral resolving power of λ/Δλ~1000. We use these data to investigate the kinematics of the narrow-line region …
The Initial Mass Function of the Galactic Bulge down to ~0.15 Msolar
Gould, Andrew; Rich, R. Michael; Frogel, Jay A. +5 more
We present a luminosity function (LF) for lower main-sequence stars in the Galactic bulge near (l,b)=(0deg,-6deg) to J=24, corresponding to MJ~9.3. This LF is derived from Hubble Space Telescope (HST) near infrared camera and multiobject spectrometer (NICMOS) observations of a region of 22.5"x22.5", with the F110W …
Ion Cyclotron Wave Dissipation in the Solar Corona: The Summed Effect of More than 2000 Ion Species
Cranmer, Steven R.
In this paper the dissipation of ion cyclotron resonant Alfvén waves in the extended solar corona is examined in detail. For the first time, the wave damping arising from more than 2000 low-abundance ion species is taken into account. Useful approximations for the computation of coronal ionization equilibria for elements heavier than nickel are pr…
Magnetic AP Stars in the Hertzsprung-Russell Diagram
Hubrig, S.; North, P.; Mathys, G.
The evolutionary state of magnetic Ap stars is rediscussed using the recently released Hipparcos data. The distribution of the magnetic Ap stars of mass below 3 Msolar in the H-R diagram differs from that of the normal stars in the same temperature range at a high level of significance. Magnetic stars are concentrated toward the center …
Weak Lensing Measurements: A Revisited Method and Application toHubble Space Telescope Images
Refregier, Alexandre; Rhodes, Jason; Groth, Edward J.
The weak distortions produced by gravitational lensing in the images of background galaxies provide a unique method to measure directly the distribution of mass in the universe. However, because the induced distortions are only of a few percent, this technique requires high-precision measurements of the lensing shear and cautious corrections for s…
The Hubble Space Telescope Key Project on the Extragalactic Distance Scale. XXV. A Recalibration of Cepheid Distances to Type IA Supernovae and the Value of the Hubble Constant
Kelson, Daniel D.; Illingworth, Garth D.; Huchra, John P. +14 more
Cepheid-based distances to seven Type Ia supernovae (SNe) host galaxies have been derived using the standard Hubble Space Telescope (HST) Key Project on the Extragalactic Distance Scale pipeline. For the first time, this allows for a transparent comparison of data accumulated as part of three different HST projects: the Key Project, the Sandage et…
Si and Mn Abundances in Damped Lyα Systems with Low Dust Content
Bowen, David V.; Pettini, Max; Ellison, Sara L. +2 more
We have measured the abundances of Zn, Si, Mn, Cr, Fe, and Ni in three damped Lyα systems at redshifts zabs<=1 from high-resolution echelle spectra of QSOs recorded with the Keck I telescope. In all three cases, the abundances of Cr, Fe, and Ni relative to Zn indicate low levels of dust depletions. We propose that when the proportion…
Yohkoh SXT and SOHO EIT Observations of Sigmoid-to-Arcade Evolution of Structures Associated with Halo Coronal Mass Ejections
Sterling, Alphonse C.; Thompson, Barbara J.; Hudson, Hugh S. +1 more
A subset of the solar-disk counterparts to halo coronal mass ejections (CMEs) displays an evolution in soft X-rays (SXR) that is characterized by a preflare S-shaped structure, dubbed a ``sigmoid,'' which evolves into a postflare cusp or arcade. We examine the morphological properties of the evolution of sigmoids into cusps and arcades for four su…
Another View of the EIT Wave Phenomenon
Delannée, C.
This paper investigates three different EIT waves. The events occurred on 1997 November 3 at 10:31 UT, on 1998 January 27 at 22:19 UT, and on 1998 June 13 at 15:23 UT and were observed with EIT on board the Solar and Heliospheric Observatory (SOHO) using the 195 Å filter that contains an Fe XII line. The three events show the following similar str…