Search Publications
COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses. X. Modeling based on high-precision astrometry of a sample of 25 lensed quasars: consequences for ellipticity, shear, and astrometric anomalies
Magain, P.; Meylan, G.; Courbin, F. +2 more
Gravitationally lensed quasars can be used as powerful cosmological and astrophysical probes. We can (i) infer the Hubble constant H0 based on the so-called time-delay technique, (ii) unveil substructures along the line-of-sight toward distant galaxies, and (iii) compare the shape and the slope of baryons and dark matter distributions i…
The double sub-giant branch of NGC 6656 (M 22): a chemical characterization
Milone, A. P.; Marino, A. F.; Zoccali, M. +14 more
We present an abundance analysis of 101 subgiant branch (SGB) stars in the globular cluster M 22. Using low-resolution FLAMES/GIRAFFE spectra we have determined abundances of the neutron-capture strontium and barium and the light element carbon. With these data we explore relationships between the observed SGB photometric split in this cluster and…
On the nature of the galactic early-B hypergiants
Howarth, I. D.; Urbaneja, M. A.; Negueruela, I. +3 more
Aims: Despite their importance to a number of astrophysical fields, the lifecycles of very massive stars are still poorly defined. In order to address this shortcoming, we present a detailed quantitative study of the physical properties of four early-B hypergiants (BHGs) of spectral type B1-4 Ia+; Cyg OB2 #12, ζ1 Sco, HD…
Far-infrared colours of nearby late-type galaxies in the Herschel Reference Survey
Clements, D. L.; Ciesla, L.; Buat, V. +21 more
We study the far infrared (60-500 µm) colours of late-type galaxies in the Herschel Reference Survey, a K-band selected, volume limited sample of nearby galaxies. The far infrared colours are correlated with each other, with tighter correlations for the indices that are closer in wavelength. We also compare the different colour indices to va…
3D simulations of Betelgeuse's bow shock
Langer, N.; Mohamed, S.; Mackey, J.
Betelgeuse, the bright, cool red supergiant in Orion, is moving supersonically relative to the local interstellar medium. The star emits a powerful stellar wind that collides with this medium, forming a cometary structure, a bow shock, pointing in the direction of motion. We present the first 3D hydrodynamic simulations of the formation and evolut…
X-ray and ultraviolet investigation into the magnetic connectivity of a solar flare
Aulanier, G.; Pariat, E.; Vilmer, N. +1 more
We investigate the X-ray and UV emission detected by RHESSI and TRACE in the context of a solar flare on the 16th November 2002 with the goal of better understanding the evolution of the flare. We analysed the characteristics of the X-ray emission in the 12-25 and 25-50 keV energy range while we looked at the UV emission at 1600 Å . The flare appe…
Dynamics of starbursting dwarf galaxies: I Zw 18
Fraternali, F.; Lelli, F.; Verheijen, M. +1 more
I Zw 18 is a prototype blue compact dwarf (BCD) galaxy, characterized by a strong starburst and extremely low metallicity (Z ~ 0.02 Z⊙). It has long been considered a candidate young galaxy in the Local Universe, but recent studies have found that it contains old stars. We analysed archival VLA observations of the 21 cm line and found t…
The Herschel Virgo Cluster Survey. X. The relationship between cold dust and molecular gas content in Virgo spirals
Bianchi, S.; Fritz, J.; Madden, S. C. +16 more
Aims: We examine whether dust mass can trace the total or molecular gas mass in late-type Virgo cluster galaxies, and how the environment affects the dust-to-gas ratio and the molecular fraction.
Methods: Using the far-infrared emission, as observed by the Herschel Virgo Cluster Survey (HeViCS), and the integrated HI 21-cm and CO J = 1-0…
Estimating turbulent velocities in the elliptical galaxies NGC 5044 and NGC 5813
Kaastra, J. S.; de Plaa, J.; Churazov, E. +5 more
Context. The interstellar and intra-cluster medium (ICM) in giant elliptical galaxies and clusters of galaxies is often assumed to be in hydrostatic equilibrium. Numerical simulations, however, show that about 5-30% of the pressure in a cluster is provided by turbulence induced by, for example, the central active galactic nucleus (AGN) and merger …
Multiwavelength campaign on Mrk 509. VIII. Location of the X-ray absorber
Kaastra, J. S.; Kriss, G. A.; Arav, N. +14 more
Aims: More than half of all active galactic nuclei show strong photoionised outflows. A major uncertainty in models for these outflows is the distance of the gas to the central black hole. We use the results of a massive multiwavelength monitoring campaign on the bright Seyfert 1 galaxy Mrk 509 to constrain the location of the outflow compone…