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Evolution in the Color-Magnitude Relation of Early-Type Galaxies in Clusters of Galaxies at z~=1
Dickinson, M.; Stanford, S. A.; Holden, B. P. +1 more
We present a study of the color evolution of elliptical and S0 galaxies in six clusters of galaxies inside the redshift range 0.78<z<1.27. For each cluster, we used imaging from the Hubble Space Telescope (HST) to determine morphological types of the galaxies. These types were determined both by an automated technique and from visual inspect…
WFI J2026-4536 and WFI J2033-4723: Two New Quadruple Gravitational Lenses
Rix, Hans-Walter; Dressler, Alan; Egami, Eiichi +3 more
We report the discovery of two new gravitationally lensed quasars, WFI J2026-4536 and WFI J2033-4723, at respective source redshifts of z=2.23 and z=1.66. Both systems are quadruply imaged and have similar PG 1115-like image configurations. WFI J2026-4536 has a maximum image separation of 1.4", a total brightness of g=16.5, and a relatively simple…
Predicted rotation signatures in MHD disc winds and comparison to DG Tau observations.
Dougados, C.; Ferreira, J.; Cabrit, S. +4 more
Motivated by the first detections of rotation signatures in the DG Tau jet (Bacciotti et al. \cite{bacciotti2002}), we examine possible biases affecting the relation between detected rotation signatures and true azimuthal velocity for self-similar MHD disc winds, taking into account projection, convolution as well as excitation gradients effects. …
Radiation-driven winds of hot luminous stars. XV. Constraints on the mass-luminosity relation of central stars of planetary nebulae
Pauldrach, A. W. A.; Hoffmann, T. L.; Méndez, R. H.
We present a new model atmosphere analysis of nine central stars of planetary nebulae. This study is based on a new generation of realistic stellar model atmospheres for hot stars; state-of-the-art, hydrodynamically consistent, spherically symmetric model atmospheres that have been shown to correctly reproduce the observed UV spectra of massive Po…
Magnetic turbulence in the plasma sheet
Balogh, A.; Zhang, T. L.; Klecker, B. +9 more
Small-scale magnetic turbulence observed by the Cluster spacecraft in the plasma sheet is investigated by means of a wavelet estimator suitable for detecting distinct scaling characteristics even in noisy measurements. The spectral estimators used for this purpose are affected by a frequency-dependent bias. The variances of the wavelet coefficient…
XMM-Newton observation of the relaxed cluster A478: Gas and dark matter distribution from 0.01R200 to 0.5R200
de Plaa, J.; Arnaud, M.; Pointecouteau, E. +1 more
We present an XMM-Newton mosaic observation of the hot (kT∼6.5 keV) and nearby (z=0.0881) relaxed cluster of galaxies A478. We derive precise gas density, gas temperature, gas mass and total mass profiles up to 12 arcmin (about half of the virial radius R200). The gas density profile is highly peaked towards the center and the surface b…
Tests of stellar model atmospheres by optical interferometry. VLTI/VINCI limb-darkening measurements of the M4 giant ψ Phe
Kervella, P.; Wittkowski, M.; Aufdenberg, J. P.
We present K-band interferometric measurements of the limb-darkened (LD) intensity profile of the M 4 giant star ψ Phoenicis obtained with the Very Large Telescope Interferometer (VLTI) and its commissioning instrument VINCI. High-precision squared visibility amplitudes in the second lobe of the visibility function were obtained employing two 8.2 …
Long-term spectral changes in the partial-covering candidate narrow-line Seyfert 1 galaxy 1H 0707-495
Brandt, W. N.; Vaughan, S.; Fabian, A. C. +3 more
We compare two XMM-Newton observations of the narrow-line Seyfert 1 galaxy 1H 0707-495, separated by two years, and discuss the results in terms of the partial-covering phenomenon. The second longer observation once again displays a sharp (<200 eV) spectral drop above 7 keV; however, in comparison with the first observation, the edge depth and …
Testing Lorentz Invariance with GRB 021206
Hurley, K.; Wunderer, C. B.; Boggs, Steven E. +1 more
Since the discovery of the cosmological origin of gamma-ray bursts (GRBs), there has been growing interest in using these transient events to probe the quantum gravity energy scale in the range 1016-1019 GeV, up to the Planck mass scale. This energy scale can manifest itself through a measurable modification in the electromag…
The Stellar Populations of Low-Luminosity Active Galactic Nuclei. II. Space Telescope Imaging Spectrograph Observations
Heckman, Timothy; Leitherer, Claus; Storchi-Bergmann, Thaisa +5 more
We present a study of the stellar populations of low-luminosity active galactic nuclei (LLAGNs). Our goal is to search for spectroscopic signatures of young and intermediate-age stars and to investigate their relationship with the ionization mechanism in LLAGNs. The method used is based on the stellar population synthesis of the optical continuum …