Search Publications
Magnetic Field Strengths in the Hot Spots and Lobes of Three Powerful Fanaroff-Riley Type II Radio Sources
Cameron, R. A.; Hardcastle, M. J.; Birkinshaw, M. +3 more
We have made deep Chandra observations of three powerful Fanaroff-Riley type II (FR II) radio sources: two quasars (3C 263 and 3C 351) and one radio galaxy (3C 330). X-ray emission from hot spots and lobes, as well as from the active nucleus, is detected in each source. We model the hot spots' synchrotron spectra using VLA, BIMA, and Hubble Space …
A Determination of H0 with the CLASS Gravitational Lens B1608+656. III. A Significant Improvement in the Precision of the Time Delay Measurements
Koopmans, L. V. E.; Fassnacht, C. D.; Rusin, D. +1 more
The gravitational lens CLASS B1608+656 is the only four-image lens system for which all three independent time delays have been measured. This makes the system an excellent candidate for a high-quality determination of H0 at cosmological distances. However, the original measurements of the time delays had large (12%-20%) uncertainties, …
Are High-Redshift Damped Lyα Galaxies Lyman Break Galaxies?
Jakobsen, P.; Fall, S. M.; Møller, P. +2 more
We use deep HST STIS and NICMOS images of three spectroscopically confirmed galaxy counterparts of high-redshift damped Lyα (DLA) absorbers (one of which is a new discovery) to test the hypothesis that high-redshift DLA galaxies are Lyman break galaxies. If this hypothesis is correct, the emission properties of DLA galaxies must lie within the ran…
Chandra Detection of a Type II Quasar at z = 3.288
Moran, Edward C.; Davis, Marc; Graham, James R. +16 more
We report on observations of a type II quasar at redshift z=3.288, identified as a hard X-ray source in a 185 ks observation with the Chandra X-Ray Observatory and as a high-redshift photometric candidate from deep, multiband optical imaging. CXO J084837.9+445352 (hereafter CXO 52) shows an unusually hard X-ray spectrum from which we infer an abso…
The HELLAS2XMM Survey. II. Multiwavelength Observations of P3: An X-Ray-bright, Optically Inactive Galaxy
Maiolino, R.; Perola, G. C.; Fiore, F. +11 more
Recent X-ray surveys have clearly demonstrated that a population of optically dull, X-ray-bright galaxies is emerging at 2-10 keV fluxes of the order of 10-14 ergs cm-2 s-1. Although they might constitute an important fraction of the sources responsible for the hard X-ray background, their nature is still unknown. …
Elemental Abundances and Post-Coronal Mass Ejection Current Sheet in a Very Hot Active Region
Raymond, J. C.; Ciaravella, A.; Fineschi, S. +4 more
A peculiar young active region was observed in 1998 March with the Ultraviolet Coronagraph Spectrometer (UVCS) over the southwest limb. The spectra showed strong emission in the λ974 line of fluorine-like iron, [Fe XVIII], which is brightest at an electron temperature of 106.8 K, and lines of Ne IX, [Ca XIV], [Ca XV], Fe XVII, [Ni XIV],…
A Mass for the Extrasolar Planet Gliese 876b Determined from Hubble Space Telescope Fine Guidance Sensor 3 Astrometry and High-Precision Radial Velocities
Butler, R. P.; McArthur, B. E.; Benedict, G. F. +9 more
We report the first astrometrically determined mass of an extrasolar planet, a companion previously detected by Doppler spectroscopy. Radial velocities first provided an ephemeris with which to schedule a significant fraction of the Hubble Space Telescope (HST) observations near companion peri- and apastron. The astrometry residuals at these orbit…
The Spectral Energy Distribution of HH 30 IRS: Constraining the Circumstellar Dust Size Distribution
Wood, Kenneth; Wolff, Michael J.; Bjorkman, J. E. +1 more
We present spectral energy distribution (SED) models for the edge-on classical T Tauri star HH 30 IRS that indicate that dust grains have grown to larger than 50 µm within its circumstellar disk. The disk geometry and inclination are known from previous modeling of multiwavelength Hubble Space Telescope images, and we use the SED (0.5µ…
Do the Infrared Emission Features Need Ultraviolet Excitation? The Polycyclic Aromatic Hydrocarbon Model in UV-poor Reflection Nebulae
Draine, B. T.; Li, Aigen
One of the major challenges to identification of the 3.3, 6.2, 7.7, 8.6, and 11.3 µm interstellar infrared (IR) emission bands with polycyclic aromatic hydrocarbon (PAH) molecules has been the recent detection of these bands in regions with little ultraviolet (UV) illumination, since small, neutral PAH molecules have little or no absorption …
The Low-Mass X-Ray Binary-Globular Cluster Connection in NGC 4472
Kundu, Arunav; Zepf, Stephen E.; Maccarone, Thomas J.
We have analyzed the low-mass X-ray binary (LMXB) candidates in a Chandra observation of the giant elliptical galaxy NGC 4472. In a region observed by the Hubble Space Telescope (HST), approximately 40% of the bright (LX>~1037 ergs s-1) LMXBs are associated with optically identified globular clusters (GC). This …