Search Publications
The dynamical mass of the young cluster W3 in NGC 7252. Heavy-weight globular cluster or ultra compact dwarf galaxy?
Saglia, R. P.; Bastian, N.; Maraston, C. +3 more
We have determined the dynamical mass of the most luminous stellar cluster known to date, i.e. object W3 in the merger remnant galaxy NGC 7252. The dynamical mass is estimated from the velocity dispersion measured with the high-resolution spectrograph UVES on VLT. Our result is the astonishingly high velocity dispersion of σ=45 ± 5 km s-1
A Substantial Population of Red Galaxies at z > 2: Modeling of the Spectral Energy Distributions of an Extended Sample
Wuyts, S.; Daddi, E.; Förster Schreiber, N. M. +12 more
We investigate the nature of the substantial population of high-redshift galaxies with Js-Ks>=2.3 colors recently discovered as part of our Faint Infrared Extragalactic Survey (FIRES). This color cut efficiently isolates galaxies at z>2 with red rest-frame optical colors (``distant red galaxies'' [DRGs]). We select J
X-ray flares reveal mass and angular momentum of the Galactic Center black hole
Grosso, N.; Porquet, D.; Predehl, P. +1 more
We have analysed the light curve of the two brightest X-ray flares from the Galactic Center black hole, one flare observed by XMM-Newton on October 3, 2002 (Porquet et al. \cite{P2003}), and the other flare observed by Chandra on October 26, 2000 (Baganoff et al. \cite{B2001}). The power density spectra show five distinct peaks at periods of ∼100 …
The Colors of Dwarf Elliptical Galaxy Globular Cluster Systems, Nuclei, and Stellar Halos
Ferguson, Henry C.; Miller, Bryan W.; Lotz, Jennifer M.
We present the results of a Hubble Space Telescope WFPC2 F555W and F814W survey of 69 dwarf elliptical galaxies (dEs) in the Virgo and Fornax Clusters and Leo Group. The V-I colors of the dE globular clusters, nuclei, and underlying field-star populations are used to trace the dE star formation histories. We find that the dE globular cluster candi…
Hard X-ray view of the past activity of Sgr A* in a natural Compton mirror
Gilfanov, M. R.; Sunyaev, R. A.; Sazonov, S. Yu. +6 more
We report the association of the recently discovered hard X-ray source IGR J17475-2822 with the giant molecular cloud Sgr B2 in the Galactic Center region. The broad band (3-200 keV) spectrum of the source constructed from data of different observatories strongly supports the idea that the X-ray emission of Sgr B2 is Compton scattered and reproces…
Observable Properties of the Breakout Model for Coronal Mass Ejections
Lynch, B. J.; MacNeice, P. J.; Antiochos, S. K. +2 more
We compare the ``magnetic breakout'' model for coronal mass ejections (CMEs) with observed general properties of CMEs by analyzing in detail recent high-resolution MHD simulations of a complete breakout CME. The model produces an eruption with a three-part plasma density structure that shows a bright circular rim outlining a dark central cavity in…
Some empirical estimates of the H2 formation rate in photon-dominated regions
Boulanger, F.; Walmsley, C. M.; Habart, E. +2 more
We combine recent ISO observations of the vibrational ground state lines of H2 towards Photon-Dominated Regions (PDRs) with observations of vibrationally excited states made with ground-based telescopes in order to constrain the formation rate of H2 on grain surfaces under the physiconditions in the layers responsible for H
A Huge Drop in the X-Ray Luminosity of the Nonactive Galaxy RX J1242.6-1119A, and the First Postflare Spectrum: Testing the Tidal Disruption Scenario
Schartel, Norbert; Komossa, Stefanie; Hasinger, Günther +3 more
In recent years, indirect evidence has emerged suggesting that many nearby nonactive galaxies harbor quiescent supermassive black holes. Knowledge of the frequency of occurrence of black holes, of their masses and spins, is of broad relevance for studying black hole growth and galaxy and active galactic nuclei formation and evolution. It has been …
A multiwavelength study of solar flare waves. I. Observations and basic properties
Magdalenić, J.; Vršnak, B.; Hanslmeier, A. +2 more
Propagating wave-like disturbances associated with solar flares - commonly observed in the chromosphere as Moreton waves - have been known for several decades. Recently, the phenomenon has come back into focus prompted by the observation of coronal waves with the SOHO/EIT instrument (``EIT waves"). It has been suggested that they represent the ant…
Analysing observed star cluster SEDs with evolutionary synthesis models: systematic uncertainties
de Grijs, R.; Anders, P.; Fritze-v. Alvensleben, U. +1 more
We discuss the systematic uncertainties inherent to analyses of observed (broad-band) spectral energy distributions (SEDs) of star clusters with evolutionary synthesis models. We investigate the effects caused by restricting oneself to a limited number of available passbands, choices of various passband combinations, finite observational errors, n…