Search Publications
The Survival of Dark Matter Halos in the Cluster Cl 0024+16
Treu, Tommaso; Ellis, Richard; Smail, Ian +5 more
Theories of structure formation in a cold dark matter dominated universe predict that massive clusters of galaxies assemble from the hierarchical merging of lower mass subhalos. Exploiting strong and weak gravitational lensing signals inferred from panoramic Hubble Space Telescope imaging data, we present a high-resolution reconstruction of the ma…
The Environments of Active Galactic Nuclei within the zCOSMOS Density Field
Finoguenov, A.; Kneib, J. -P.; Jahnke, K. +58 more
The impact of environment on active galactic nucleus (AGN) activity up to z ~ 1 is assessed by utilizing a mass-selected sample of galaxies from the 10k catalog of the zCOSMOS spectroscopic redshift survey. We identify 147 AGN by their X-ray emission as detected by XMM-Newton from a parent sample of 7234 galaxies. We measure the fraction of galaxi…
Linking Remote Imagery of a Coronal Mass Ejection to Its In Situ Signatures at 1 AU
Möstl, C.; Farrugia, C. J.; Temmer, M. +5 more
In a case study (2008 June 6-7) we report on how the internal structure of a coronal mass ejection (CME) at 1 AU can be anticipated from remote observations of white-light images of the heliosphere. Favorable circumstances are the absence of fast equatorial solar wind streams and a low CME velocity which allow us to relate the imaging and in situ …
Gemini Spectroscopic Survey of Young Star Clusters in Merging/Interacting Galaxies. III. The Antennae
Miller, Bryan W.; Konstantopoulos, Iraklis S.; Trancho, Gelys +1 more
We present optical spectroscopy of 16 star clusters in the merging galaxies NGC 4038/39 ("the Antennae") and supplement this data set with Hubble Space Telescope imaging. The age and metallicity of each cluster is derived through a comparison between the observed Balmer and metal line strengths with simple stellar population models. We then estima…
Globular cluster systems in nearby dwarf galaxies - I. HST/ACS observations and dynamical properties of globular clusters at low environmental density
Georgiev, Iskren Y.; Goudfrooij, Paul; Puzia, Thomas H. +1 more
We investigate the old globular cluster (GC) population of 68 faint (MV > -16mag) dwarf galaxies located in the halo regions of nearby (<~12Mpc) loose galaxy groups and in the field environment based on archival Hubble Space Telescope (HST)/Advanced Camera for Surveys (ACS) images in F606W and F814W filters. The combined colour di…
Nonlinear Force-free Modeling of a Long-lasting Coronal Sigmoid
van Ballegooijen, Adriaan; Savcheva, Antonia
A study of the magnetic configuration and evolution of a long-lasting quiescent coronal sigmoid is presented. The sigmoid was observed by Hinode/XRT and Transition Region and Coronal Explorer (TRACE) between 2007 February 6 and 12 when it finally erupted. We construct nonlinear force-free field models for several observations during this period, u…
The haze and methane distributions on Uranus from HST-STIS spectroscopy
Karkoschka, Erich; Tomasko, Martin
We analyzed a unique, three-dimensional data set of Uranus acquired with the STIS Hubble spectrograph on August 19, 2002. The data covered a full afternoon hemisphere at 0.1 arc-sec spatial resolution between 300 and 1000 nm wavelength at 1 nm resolution. Navigation was accurate to 0.002 arc-sec and 0.02 nm. We tested our calibration with WFPC2 im…
Scaling Laws of Turbulence and Heating of Fast Solar Wind: The Role of Density Fluctuations
Bruno, R.; Carbone, V.; Sorriso-Valvo, L. +2 more
Incompressible and isotropic magnetohydrodynamic turbulence in plasmas can be described by an exact relation for the energy flux through the scales. This Yaglom-like scaling law has been recently observed in the solar wind above the solar poles observed by the Ulysses spacecraft, where the turbulence is in an Alfvénic state. An analogous phenomeno…
Study of the Spectral and Temporal Characteristics of X-Ray Emission of the Gamma-Ray Binary LS 5039 with Suzaku
Yamaoka, Kazutaka; Takahashi, Tadayuki; Uchiyama, Yasunobu +6 more
We report on the results from Suzaku broadband X-ray observations of the galactic binary source LS 5039. The Suzaku data, which have continuous coverage of more than one orbital period, show strong modulation of the X-ray emission at the orbital period of this TeV gamma-ray emitting system. The X-ray emission shows a minimum at orbital phase ~0.1,…
Constraining jet/disc geometry and radiative processes in stellar black holes XTE J1118+480 and GX 339-4
Nowak, Michael; Wilms, Jörn; Markoff, Sera +3 more
We present results from modelling of quasi-simultaneous broad-band (radio through X-ray) observations of the Galactic stellar black hole (BH) transient X-ray binary (XRB) systems XTE J1118+480 and GX 339-4 using an irradiated disc + compact jet model. In addition to quantifying the physical properties of the jet, we have developed a new irradiated…