Search Publications
An improved deprojection and PSF-deconvolution technique for galaxy-cluster X-ray surface-brightness profiles
Arnaud, M.; Pointecouteau, E.; Pratt, G. W. +1 more
We have developed a regularisation procedure for the direct deprojection and PSF-deconvolution of X-ray surface brightness profiles of clusters of galaxies. This procedure allows us to obtain accurate density profiles in a straightforward manner from X-ray observations (in particular data from XMM-Newton, where the PSF correction is important), wh…
The evolution of Lyman α absorbers in the redshift range 0.5 < z < 1.9
Reimers, D.; Janknecht, E.; Lopez, S. +1 more
We investigate the evolution and the statistical properties of the Ly α absorbers of the intergalactic medium (IGM) in the largely unexplored redshift range z=0.5-1.9. We use high-resolution (R ≥ 30 000) UV (STIS) and optical (VLT/UVES and Keck/HIRES) spectra of nine bright quasars with z_em < 1.94. The Ly α lines detected in the lines of sight…
XMM-Newton observations of a sample of γ-ray loud active galactic nuclei
Maraschi, L.; Tagliaferri, G.; Ghisellini, G. +7 more
Aims.To understand the nature of γ-ray loud active galactic nuclei (AGN) and the mechanisms for the generation of high-energy γ-rays.
Methods: .We performed a homogeneous and systematic analysis of simultaneous X-ray and optical/UV properties of a group of 15 γ-ray loud AGN, using observations performed with XMM-Newton. The sample is composed …
Ultraviolet-to-far infrared properties of Lyman break galaxies and luminous infrared galaxies at z ~ 1
Ilbert, O.; Buat, V.; Burgarella, D. +13 more
Aims.We present the first large, unbiased sample of Lyman Break Galaxies (LBGs) at z ∼ 1. Far ultraviolet-dropout (1530 Å) galaxies in the Chandra Deep Field South have been selected using GALEX data. This first large sample in the z ∼ 1 universe provides us with a high quality reference sample of LBGs.
Methods: .We analyzed the sample from t…
What is the spatial distribution of magnetic helicity injected in a solar active region?
Démoulin, P.; Pariat, E.; Nindos, A. +1 more
Context: .Magnetic helicity is suspected to play a key role in solar phenomena such as flares and coronal mass ejections. Several investigations have recently computed the photospheric flux of magnetic helicity in active regions. The derived spatial maps of the helicity flux density, called G_A, have an intrinsic mixed-sign patchy distribution.
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…