Search Publications
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…
GREAT confirms transient nature of the circum-nuclear disk
Martín-Pintado, J.; Harris, A. I.; Stutzki, J. +6 more
We report SOFIA/GREAT, Herschel/HIFI, and ground-based velocity-resolved spectroscopy of carbon monoxide (CO) rotational transitions from J = 2-1 to J = 16-15 toward two positions in the circum-nuclear disk (CND) in our Galactic center. Radiative transfer models were used to derive information on the physical state of the gas traced by CO. The exc…
Modelling the huge, Herschel-resolved debris ring around HD 207129
Magain, P.; Krivov, A. V.; Eiroa, C. +18 more
Debris disks, which are inferred from the observed infrared excess to be ensembles of dust, rocks, and probably planetesimals, are common features of stellar systems. As the mechanisms of their formation and evolution are linked to those of planetary bodies, they provide valuable information. The few well-resolved debris disks are even more valuab…
Orion revisited. I. The massive cluster in front of the Orion nebula cluster
Bouy, H.; Alves, J.
Aims: The aim of this work is to characterize the stellar population between Earth and the Orion A molecular cloud where the well-known star formation benchmark Orion nebula cluster (ONC) is embedded.
Methods: We used the denser regions the Orion A cloud to block optical background light, effectively isolating the stellar population in f…
AKARI observations of ice absorption bands towards edge-on young stellar objects
Tamura, M.; Kandori, R.; Pontoppidan, K. M. +9 more
Context. Circumstellar disks and envelopes of low-mass young stellar objects (YSOs) contain significant amounts of ice. Such icy material will evolve to become volatile components of planetary systems, such as comets in our solar system.
Aims: To investigate the composition and evolution of circumstellar ice around low-mass young stellar obje…
Star formation and disk properties in Pismis 24
Henning, Th.; van Boekel, R.; Fang, M. +6 more
Context. Circumstellar disks are expected to evolve quickly in massive young clusters harboring many OB-type stars. Two processes have been proposed to drive the disk evolution in such cruel environments: (1) gravitational interaction between circumstellar disks and nearby passing stars (stellar encounters); and (2) photoevaporation by UV photons …
Molecular line survey of the high-mass star-forming region NGC 6334I with Herschel/HIFI and the Submillimeter Array
Ceccarelli, C.; Comito, C.; Schilke, P. +7 more
Aims: We aim at deriving the molecular abundances and temperatures of the hot molecular cores in the high-mass star-forming region NGC 6334I and consequently deriving their physical and astrochemical conditions.
Methods: In the framework of the Herschel guaranteed time key program CHESS (Chemical HErschel Surveys of Star forming regions)…
Transient dust in warm debris disks. Detection of Fe-rich olivine grains
Mutschke, H.; Ábrahám, P.; Henning, Th. +4 more
Context. Debris disks trace remnant reservoirs of leftover planetesimals in planetary systems. In the past years, a handful of "warm" debris disks have been discovered in which emission in excess starts in the mid-infrared. An interesting subset of these warm debris disks shows emission features in mid-infrared spectra, which points towards the pr…
A DEBRIS disk around the planet hosting M-star GJ 581 spatially resolved with Herschel
Duchêne, G.; Dent, W. R. F.; Bryden, G. +17 more
Debris disks have been found primarily around intermediate and solar mass stars (spectral types A-K) but rarely around low mass M-type stars. We have spatially resolved a debris disk around the remarkable M3-type star GJ 581 hosting multiple planets using deep PACS images at 70, 100 and 160 µm as part of the DEBRIS Program on the Herschel Sp…