Search Publications
Microquasars as sources of positron annihilation radiation
Guessoum, N.; Jean, P.; Prantzos, N.
We consider the production of positrons in microquasars, i.e. X-ray binary systems that exhibit jets frequently, but not continuously. We estimate the production rate of positrons in microquasars, both by simple energy considerations and in the framework of various proposed models. We then evaluate the collective emissivity of the annihilation rad…
The clustering evolution of distant red galaxies in the GOODS-MUSIC sample
Fontana, A.; Vanzella, E.; Grazian, A. +8 more
Aims.We study the clustering properties of Distant Red Galaxies (DRGs) to test whether they are the progenitors of local massive galaxies.
Methods.We use the GOODS-MUSIC sample, a catalog of ~3000 Ks-selected galaxies based on VLT and HST observation of the GOODS-South field with extended multi-wavelength coverage (from 0.3 to 8~µm) and …
Measuring supermassive black holes with gas kinematics: the active S0 galaxy NGC 3998
Marconi, A.; Capetti, A.; de Francesco, G.
Context: .We present results from a kinematical study of the gas in the nucleus of the active S0 galaxy NGC 3998 obtained from archival HST/STIS long-slit spectra.
Aims: .We analyzed the emission lines profiles and derived the map of the gas velocity field. The observed velocity curves are consistent with gas in regular rotation around the gal…
The near-infrared luminosity function of cluster galaxies beyond redshift one
Demarco, R.; Lidman, C.; Toft, S. +7 more
Aims.We determined the Ks band luminosity function (LF), and inferred the corresponding stellar mass function, of cluster galaxies at redshift z≃ 1.2, using near-infrared images of three X-ray luminous clusters at z=1.11,1.24,1.27.
Methods: .The composite LF was derived down to M*+4, by means of statistical background sub…
Vertical distribution of Galactic disk stars
Soubiran, C.; Siebert, A.; Bienaymé, O. +2 more
We used red clump stars to measure the surface mass density of the Galactic disk in the solar neighbourhood. High resolution spectra of red clump stars towards the NGP have been obtained with the ELODIE spectrograph at OHP for Tycho-2 selected stars, and nearby Hipparcos counterparts were also observed. We determined their distances, velocities, a…
Electron acceleration by the reconnection outflow shock during solar flares
Mann, G.; Aurass, H.; Warmuth, A.
During solar flares a large amount of nonthermal electromagnetic radiation up to the γ-ray range is emitted from the corona, which implies that energetic electrons are generated. Within the framework of the magnetic reconnection scenario, jets appear in the outflow region and can establish standing fast-mode shocks if they penetrate the surroundin…
Modeling the Sun's open magnetic flux
Schüssler, M.; Baumann, I.
Context: .The heliospheric magnetic field can be extrapolated from the photospheric field distribution using models based upon various approximations. Such models are required for the reconstruction of the open solar magnetic flux prior to the time of direct measurements on the basis of surface flux transport simulations.
Aims: .We evaluate th…
Simulations of galactic winds and starbursts in galaxy clusters
van Kampen, E.; Schindler, S.; Breitschwerdt, D. +7 more
We present an investigation of the metal enrichment of the intra-cluster medium (ICM) by galactic winds and merger-driven starbursts. We use combined N-body/hydrodynamic simulations with a semi-numerical galaxy formation model. The mass loss by galactic winds is obtained by calculating transonic solutions of steady state outflows, driven by therma…
Radio and X-ray variability of young stellar objects in the Coronet cluster
Menten, K. M.; Forbrich, J.; Preibisch, Th.
The Coronet cluster in the nearby R CrA dark cloud offers the rare opportunity to study at least four "class I" protostellar sources as well as one candidate "class 0" source, a Herbig Ae star, and a candidate brown dwarf within a few square arcminutes - most of them detected at radio- and X-ray wavelengths. These sources were observed with the Ve…
Multiplicity of very low-mass objects in the Upper Scorpius OB association: a possible wide binary population
Béjar, V. J. S.; Schirmer, M.; Ghez, A. M. +5 more
Aims.Properties of multiplicity, such as the multiplicity frequency, the distribution of mass ratios and periods, provide important informations on the formation processes at work. Studying these properties in different environments and at different ages allows us to constrain the models of formation and to understand the influence of the environm…