Search Publications
The Herschel Virgo Cluster Survey. IX. Dust-to-gas mass ratio and metallicity gradients in four Virgo spiral galaxies
Bianchi, S.; Smith, M.; Fritz, J. +20 more
Context. Using Herschel data from the open time key project the Herschel Virgo Cluster Survey (HeViCS), we investigated the relationship between the metallicity gradients expressed by metal abundances in the gas phase as traced by the chemical composition of HII regions, and in the solid phase, as traced by the dust-to-gas mass ratio.
Aims: W…
Inferring the magnetic field vector in the quiet Sun. I. Photon noise and selection criteria
Borrero, J. M.; Kobel, P.
In the past, spectropolarimetric data from Hinode/SP were employed to infer the distribution of the magnetic field vector in the quiet Sun. While some authors found predominantly horizontal magnetic fields, others favor an isotropic distribution. We investigate whether it is actually possible to accurately retrieve the magnetic field vector in reg…
Concurrent X-ray, near-infrared, sub-millimeter, and GeV gamma-ray observations of Sagittarius A*
Genzel, R.; Rouan, D.; Ponti, G. +13 more
Aims: The radiative counterpart of the supermassive black hole at the Galactic center (GC), Sgr A⋆, is subject to frequent flares that are visible simultaneously in X-rays and the near-infrared (NIR). Often, enhanced radio variability from centimeter to sub-millimeter wavelengths is observed to follow these X-ray/NIR eruptions. We …
The upper atmosphere of the exoplanet HD 209458 b revealed by the sodium D lines. Temperature-pressure profile, ionization layer, and thermosphere
Moutou, C.; Ehrenreich, D.; Ferlet, R. +6 more
A complete reassessment of the Hubble Space Telescope (HST) observations of the transits of the extrasolar planet HD 209458 b has provided a transmission spectrum of the atmosphere over a wide range of wavelengths. Analysis of the NaI absorption line profile has already shown that the sodium abundance has to drop by at least a factor of ten above …
Detection of CH+ emission from the disc around HD 100546
Pinte, C.; Ménard, F.; Woitke, P. +13 more
Despite its importance in the thermal balance of the gas and in the determination of primeval planetary atmospheres, the chemistry in protoplanetary discs remains poorly constrained with only a handful of detected species. We observed the emission from the disc around the Herbig Be star
Solar irradiance variability: a six-year comparison between SORCE observations and the SATIRE model
Krivova, N. A.; Solanki, S.; Harder, J. W. +2 more
Aims: We investigate how well modeled solar irradiances agree with measurements from the SORCE satellite, both for total solar irradiance and broken down into spectral regions on timescales of several years.
Methods: We use the SATIRE model and compare modeled total solar irradiance (TSI) with TSI measurements over the period 25 February…
How old are the stars in the halo of NGC 5128 (Centaurus A)?
Rejkuba, M.; Greggio, L.; Harris, W. E. +1 more
Context. NGC 5128 (Centaurus A) is, at the distance of just 3.8 Mpc, the nearest easily observable giant elliptical galaxy. Therefore it is the best target to investigate the early star formation history of an elliptical galaxy.
Aims: Our aims are to establish when the oldest stars formed in NGC 5128, and whether this galaxy formed stars over…
Multiwavelength campaign on Mrk 509. I. Variability and spectral energy distribution
Kaastra, J. S.; Kriss, G. A.; Arav, N. +23 more
Context. Active galactic nuclei (AGN) show a wealth of interesting physical processes, some of which are poorly understood. In a broader context, they play an important role in processes that are far beyond their immediate surroundings, owing to the high emitted power.
Aims: We want to address a number of open questions, including the locatio…
Spectral energy distributions of an AKARI-SDSS-GALEX sample of galaxies
Buat, V.; Burgarella, D.; Noll, S. +5 more
Context. The nearby universe remains the best laboratory to understand the physical properties of galaxies and is a reference for any comparison with high redshift observations. The all sky (or very large) surveys that have been performed from the ultraviolet (UV) to the far-infrared (far-IR) provide us with large datasets of very large wavelength…
Resolved photometry of extragalactic young massive star clusters
Bastian, N.; Larsen, S. S.; Smith, L. J. +6 more
Aims: We present colour-magnitude diagrams (CMDs) of young massive star clusters in several galaxies located well beyond the Local Group. The richness of these clusters allows us to obtain large samples of post-main sequence stars and test how well the observed CMDs are reproduced by canonical stellar isochrones.
Methods: We use imaging …