Context. CoRoT is a space telescope dedicated to stellar seismology and the search for extrasolar planets. The mission is led by the CNES in association with French laboratories and has a large international participation. The European Space Agency (ESA), Austria, Belgium, and Germany contribute to the payload, and Spain and Brazil contribute to the ground segment. Development of the spacecraft, which is based on a PROTEUS low earth orbit (LEO) recurrent platform, commenced in October 2000, and the satellite was launched on December 27, 2006. Aims. The instrument and platform characteristics prior to launch have been described in ESA publication (SP-1306). In the present paper we explain the behaviour in flight, based on raw and corrected data. Methods. Five runs have been completed since January 2007. The data used here are essentially those acquired during the commissioning phase and from a long run that lasted 146 days. These enable us to give a complete overview of the instrument and platform behaviour for all environmental conditions. The ground based data processing is not described in detail because the most important method has been published elsewhere. Results. We show that the performance specifications are easily satisfied when the environmental conditions are favourable. Most of the perturbations, hence data corrections, are related to LEO perturbations: high energy particles inside the South Atlantic Anomaly (SAA), eclipses and temperature variations, and line of sight fluctuations due to the attitude control system. Straylight due to the reflected light from the earth, which is controlled by the telescope and baffle design, appears to be negligible.

Understanding the mechanisms that lead dense environments to host galaxies with redder colors, more spheroidal morphologies, and lower star formation rates than field populations remains an important problem. As most candidate processes ultimately depend on host halo mass, accurate characterizations of the local environment, ideally tied to halo mass estimates and spanning a range in halo mass and redshift are needed. In this work, we present and test a rigorous, probabalistic method for assigning galaxies to groups based on precise photometric redshifts and X-ray selected groups drawn from the COSMOS field. The groups have masses in the range 10 13 M 200c /M 10 14 and span redshifts 0 < z < 1. We characterize our selection algorithm via tests on spectroscopic subsamples, including new data obtained at the VLT, and by applying our method to detailed mock catalogs. We find that our group member galaxy sample has a purity of 84% and completeness of 92% within 0.5R 200c . We measure the impact of uncertainties in redshifts and group centering on the quality of the member selection with simulations based on current data as well as future imaging and spectroscopic surveys. As a first application of our new group member catalog which will be made publicly available, we show that member galaxies exhibit a higher quenched fraction compared to the field at fixed stellar mass out to z ∼ 1, indicating a significant relationship between star formation and environment at group scales. We also address the suggestion that dusty star forming galaxies in such groups may impact the high-power spectrum of the cosmic microwave background and find that such a population cannot explain the low power seen in recent SZ measurements.

We present accurate time delays for the quadruply imaged quasar HE 0435-1223. The delays were measured from 575 independent photometric points obtained in the R-band between January 2004 and March 2010. With seven years of data, we clearly show that quasar image A is affected by strong microlensing variations and that the time delays are best expressed relative to quasar image B. We measured Δt BC = 7.8 ± 0.8 days, Δt BD = −6.5 ± 0.7 days and Δt CD = −14.3 ± 0.8 days. We spacially deconvolved HST NICMOS2 F160W images to derive accurate astrometry of the quasar images and to infer the light profile of the lensing galaxy. We combined these images with a stellar population fitting of a deep VLT spectrum of the lensing galaxy to estimate the baryonic fraction, f b , in the Einstein radius. We measured f b = 0.65 The spectrum also allowed us to estimate the velocity dispersion of the lensing galaxy, σ ap = 222 ± 34 km s −1 . We used f b and σ ap to constrain an analytical model of the lensing galaxy composed of an Hernquist plus generalized NFW profile. We solved the Jeans equations numerically for the model and explored the parameter space under the additional requirement that the model must predict the correct astrometry for the quasar images. Given the current error bars on f b and σ ap , we did not constrain H 0 yet with high accuracy, i.e., we found a broad range of models with χ 2 < 1. However, narrowing this range is possible, provided a better velocity dispersion measurement becomes available. In addition, increasing the depth of the current HST imaging data of HE 0435-1223 will allow us to combine our constraints with lens reconstruction techniques that make use of the full Einstein ring that is visible in this object. Key words. cosmological parameters -gravitational lensing: strong Based on observations made with the 1.2 m Euler Swiss Telescope, the 1.5 m telescope of Maidanak Observatory in Uzbekistan, and with the 1.2 m Mercator Telescope, operated on the island of La Palma by the Flemish Community, at the Spanish Observatorio del Roque de los

The existence of strong lensing systems with Einstein radii covering the full mass spectrum, from ∼ 1 − 2 (produced by galaxy scale dark matter haloes) to > 10 (produced by galaxy cluster scale haloes) have long been predicted. Many lenses with Einstein radii around 1 − 2 and above 10 have been reported but very few in between. In this article, we present a sample of 13 strong lensing systems with Einstein radii in the range 3 − 8 (or image separations in the range 6 − 16 ), i.e. systems produced by galaxy group scale dark matter haloes. This group sample spans a redshift range from 0.3 to 0.8. This opens a new window of exploration in the mass spectrum, around 10 13 -10 14 M , a crucial range for understanding the transition between galaxies and galaxy clusters, and a range that have not been extensively probed with lensing techniques. These systems constitute a subsample of the Strong Lensing Legacy Survey (SL2S), which aims to discover strong lensing systems in the Canada France Hawaii Telescope Legacy Survey (CFHTLS). The sample is based on a search over 100 square degrees, implying a number density of ∼ 0.13 groups per square degree. Our analysis is based on multi-colour CFHTLS images complemented with Hubble Space Telescope imaging and ground based spectroscopy. Large scale properties are derived from both the light distribution of elliptical galaxies group members and weak lensing of the faint background galaxy population. On small scales, the strong lensing analysis yields Einstein radii between 2.5 and 8 . On larger scales, strong lens centres coincide with peaks of light distribution, suggesting that light traces mass. Most of the luminosity maps have complicated shapes, implying that these intermediate mass structures may be dynamically young. A weak lensing signal is detected for 6 groups and upper limits are provided for 6 others. Fitting the reduced shear with a Singular Isothermal Sphere, we find σ SIS ∼ 500 km s −1 with large error bars and an upper limit of ∼ 900 km s −1 for the whole sample (except for the highest redshift structure whose velocity dispersion is consistent with that of a galaxy cluster). The mass-to-light ratio for the sample is found to be M/L i ∼ 250 (solar units, corrected for evolution), with an upper limit of 500. This compares with mass-to-light ratios of small groups (with σ SIS ∼ 300 km s −1 ) and galaxy clusters (with σ SIS > 1 000 km s −1 ), thus bridging the gap between these mass scales. The group sample released in this paper will be complemented with other observations, providing a unique sample to study this important intermediate mass range in further detail.

We present a large robust sample of 1503 reliable and unconfused 70 µm selected sources from the multiwavelength data set of the Cosmic Evolution Survey (COSMOS). Using the Spitzer IRAC and MIPS photometry, we estimate the total infrared luminosity, L IR (8-1000 µm), by finding the best fit template from several different template libraries. The long wavelength 70 and 160 µm data allow us to obtain a reliable estimate of L IR , accurate to within 0.2 and 0.05 dex, respectively. The 70 µm data point enables a significant improvement over the luminosity estimates possible with only a 24 µm detection. The full sample spans a wide range in L IR , L IR ≈ 10 8 − 10 14 L , with a median luminosity of 10 11.4 L . We identify a total of 687 luminous, 303 ultraluminous, and 31 hyperluminous infrared galaxies (LIRGs, ULIRGs, and HyLIRGs) over the redshift range 0.01 < z < 3.5 with a median redshift of 0.5. Presented here are the full spectral energy distributions for each of the sources compiled from the extensive multiwavelength data set from the ultraviolet (UV) to the far-infrared (FIR). A catalog of the general properties of the sample (including the photometry, redshifts, and L IR ) are included with this paper. We find that the overall shape of the spectral energy distribution (SED) and trends with L IR (e.g., IR color temperatures and optical-IR ratios) are similar to what has been seen in studies of local objects, however, our large sample allows us to see the extreme spread in UV to nearinfrared (NIR) colors spanning nearly three orders of magnitude. In addition, using SED fits we find possible evidence for a subset of cooler ultraluminous objects than observed locally. However, until direct observations at longer wavelengths are obtained, the peak of emission and the dust temperature cannot be well constrained. We use these SEDs, along with the deep radio and X-ray coverage of the field, to identify a large sample of candidate active galactic nuclei (AGN). We find that the fraction of AGN increases strongly with L IR , as it does in the local universe, and that nearly 70% of ULIRGs and all HyLIRGs likely host a powerful AGN.