Search Publications
X-ray spectral imaging and Doppler mapping of Cassiopeia A
Kaastra, J. S.; Vink, J.; Bleeker, J. A. M. +2 more
We present a detailed X-ray spectral analysis of Cas A using a deep exposure from the EPIC-MOS cameras on-board XMM-Newton. Spectral fitting was performed on a 15x15 grid of 20″ x 20″ pixels using a two component non-equilibrium ionisation model (NEI) giving maps of ionisation age, temperature, interstellar column density, abundances for Ne, Mg, S…
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…
Abundances of Deuterium, Nitrogen, and Oxygen in the Local Interstellar Medium: Overview of First Results from the FUSE Mission
Kruk, J. W.; Savage, B. D.; Shull, J. M. +33 more
Observations obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) have been used to determine the column densities of D I, N I, and O I along seven sight lines that probe the local interstellar medium (LISM) at distances from 37 to 179 pc. Five of the sight lines are within the Local Bubble, and two penetrate the surrounding H I wall. R…
Astrometry with the Hubble Space Telescope: A Parallax of the Fundamental Distance Calibrator RR Lyrae
McArthur, B. E.; Franz, O. G.; Bradley, A. J. +16 more
We present an absolute parallax and relative proper motion for the fundamental distance scale calibrator, RR Lyrae. We obtain these with astrometric data from FGS 3, a white-light interferometer on the Hubble Space Telescope. We find πabs=3.82+/-0.2 mas. Spectral classifications and VRIJHKT2M and DDO 51 photometry of the astr…
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.…
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 …
Galaxy cores as relics of black hole mergers
van den Bosch, Frank C.; Rest, Armin; Merritt, David +1 more
We investigate the hypothesis that the cores of elliptical galaxies and bulges are created from the binding energy liberated by the coalescence of supermassive binary black holes during galaxy mergers. Assuming that the central density profiles of galaxies were initially steep power laws, ρ ~r -2 , we define the `mass deficit' as the ma…
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…
An empirical calibration of star formation rate estimators
Terlevich, Roberto; Terlevich, Elena; Rosa-González, Daniel
The observational determination of the behaviour of the star formation rate (SFR) with look-back time or redshift has two main weaknesses: (i) the large uncertainty of the dust/extinction corrections, and (ii) that systematic errors may be introduced by the fact that the SFR is estimated using different methods at different redshifts. Most frequen…