"Proto-groups at z∼2 in zCOSMOS-deep"

Catrina DIENER (ETH Zurich)

Abstract

The zCOSMOS-deep sample contains 3500 galaxies with spectroscopic redshifts between 1.8 < z < 3 in the COSMOS field. We devise a group finder that takes into account the large measurement uncertainties at this redshift and identified 42 associations in this redshift range. They each contain three to five galaxies that lie within 500 kpc in projected distance and within 700 km/s in velocity. Based on the extensive analysis of mock catalogues generated from the Millennium simulation, I will discuss the properties of the observed structures as well as their evolution until redshift zero. Furthermore I will present a proto-cluster at redshift z = 2.45, that was dis- covered recently in follow-up observations of 7 of the proto-groups in zCOSMOS- deep. This interesting structure has so far 11 spectroscopically confirmed mem- bers.

"Magnetic star-disk interaction and the angular momentum evolution of young stars"

Jerome BOUVIER (Institut de Planetologie et d'Astrophysique de Grenoble, IPAG)

Abstract

Young solar-type stars, the so-called T Tauri stars, possess strong and complex magnetic fields, whose strength and topology are now directly measured through spectropolarimetric techniques. These strong fields disrupt the inner accretion disk over a distance of a few stellar radii, thus leading to magnetic funnel flows connecting the disk inner edge to the central star. Accretion shocks are expected to develop at the stellar surface near the magnetic poles, as the magnetically-channeled free-falling material hits the photosphere. Also, a non axisymmetric inner disk warp is expected to result from the interaction with an inclined stellar magnetosphere, which lifts up the disk material away from the central plane. In this talk, I will provide a summary of the observational evidence we have for magnetospheric accretion in young stars (magnetic fields, funnel flows, hot spots, disk warps) and will show how new COROT+Spitzer simultaneous observations nicely support and generalize this view. I will briefly mention how planetary migration may be affected by this process and will insist on the central role magnetospheric accretion plays in our current understanding of the angular momentum evolution of young stars. Finally, I will highlight the tentative causal links that appear to emerge between protoplanetary disk lifetimes, massive planet formation, rotational evolution, and lithium depletion in solar-type stars.

"Exploring giant planet aurorae with emissions from H3+"

Henrik MALIN (U. Leicester)

Abstract

The auroral process is when energetic particles impact upon the atmosphere, producing emissions. By observing these emissions we can not only glean the physical properties of the medium from which they were emitted, we can also address of the particle precipitation and physical process that delivered the particles upon the atmosphere. In the infrared, emission produced by this phenomenon can be observed from the molecular ion H3+. In this seminar, we explore what we can learn about the auroral process at Jupiter, Saturn, Uranus, and Neptune by observing emissions from H3+.

"Cepheids in Galactic Open Clusters: An All-sky Census in 8D"

Richard ANDERSON (Obs. de Geneve)

Abstract

We report on our recent eight-dimensional all-sky census of Cepheids belonging to Galactic open clusters that employs spatial, kinematic, and population-specific data. Our analysis has allowed us to confirm 15 cluster Cepheids (CCs) known in the literature and to identify 5 very good candidate CCs. Details on the analysis, including data selection and homogenization are provided. In addition to the literature data employed, we conducted observational radial velocity campaigns on both hemispheres. This program led to the discovery of the spectroscopic binary nature of at least 8 Cepheids. Some of these cases are highlighted here, including one for which a precise orbital solution was obtained. Our data mining approach to membership has the benefit of being transparent and self-consistent, and enables ranking of membership confidence according to the probabilities computed. However, some limitations of the literature data, especially for open clusters, are apparent. These limitations are discussed in the context of a calibration of the Galactic period-luminosity relationship using our bona-fide CC sample. Our method will find application in upcoming large surveys such as LSST and Gaia.

"In and around Cygnus OB2"

Fernando COMERON (ESO, Chile)

Abstract

TBA