The Wide Field Camera Transit Survey is a pioneer program aiming at for searching extra-solar planets in the near-infrared. The images from the survey are processed by a data reduction pipeline,... Show moreThe Wide Field Camera Transit Survey is a pioneer program aiming at for searching extra-solar planets in the near-infrared. The images from the survey are processed by a data reduction pipeline, which uses aperture photometry to construct the light curves. We produce an alternative set of light curves using the difference-imaging method for the most complete field in the survey and carry out a quantitative comparison between the photometric precision achieved with both methods. The results show that difference-photometry light curves present an important improvement for stars with J {gt} 16. We report an implementation on the box-fitting transit detection algorithm, which performs a trapezoid-fit to the folded light curve, providing more accurate results than the box-fitting model. We describe and optimize a set of selection criteria to search for transit candidates, including the V-shape parameter calculated by our detection algorithm. The optimized selection criteria are applied to the aperture photometry and difference-imaging light curves, resulting in the automatic detection of the best 200 transit candidates from a sample of ~{}475 000 sources. We carry out a detailed analysis in the 18 best detections and classify them as transiting planet and eclipsing binary candidates. We present one planet candidate orbiting a late G-type star. No planet candidate around M-stars has been found, confirming the null detection hypothesis and upper limits on the occurrence rate of short-period giant planets around M-dwarfs presented in a prior study. We extend the search for transiting planets to stars with J {le} 18, which enables us to set a stricter upper limit of 1.1%. Furthermore, we present the detection of five faint extremely-short period eclipsing binaries and three M-dwarf/M-dwarf binary candidates. The detections demonstrate the benefits of using the difference-imaging light curves, especially when going to fainter magnitudes. Show less
Strazzullo, V.; Rosati, P.; Pannella, M.; Gobat, R.; Santos, J.S.; Nonino, M.; ... ; Postman, M. 2010
We present a multi-wavelength study of galaxy populations in the core of the massive, X-ray luminous cluster XMMU J2235 at z = 1.39, based on high quality VLT and HST photometry at optical and near... Show moreWe present a multi-wavelength study of galaxy populations in the core of the massive, X-ray luminous cluster XMMU J2235 at z = 1.39, based on high quality VLT and HST photometry at optical and near-infrared wavelengths. We derive luminosity functions in the z, H, and Ks bands, approximately corresponding to restframe U, R and z band. These show a faint-end slope consistent with being flat, and a characteristic magnitude M* close to passive evolution predictions of M* of local massive clusters, with a formation redshift z > 2. The color-magnitude and color-mass diagrams show evidence of a tight red sequence (intrinsic scatter less than or similar to 0.08) of massive galaxies already in place, with overall old stellar populations and generally early-type morphology. Beside the red colors, these massive (>6 x 10(10) M-circle dot) galaxies typically show early-type spectral features, and rest-frame far-UV emission consistent with very low star formation rates (SFR < 0.2 M-circle dot yr(-1)). Star forming spectroscopic members, with SFR of up to similar to 100 M-circle dot/yr, are all located at clustercentric distances greater than or similar to 250 kpc, with the central cluster region already appearing effectively quenched. Most part of the cluster galaxies more massive than 6 x 10(10) M-circle dot within the studied area do not appear to host significant levels of star formation. The high-mass end of the galaxy populations in the core of this cluster appears to be in a very advanced evolutionary stage, not only in terms of formation of the stellar populations, but also of the assembly of the stellar mass. The high-mass end of the galaxy stellar mass function is essentially already in place. The stellar mass fraction estimated within r(500) (similar to 1%, Kroupa IMF) is already similar to that of local massive clusters. On the other hand, surface brightness distribution modeling of the massive red sequence galaxies may suggest that their size is often smaller than expected based on the local stellar mass vs. size relation. An evolution of the stellar mass vs. size relation might imply that, in spite of the overall early assembly of these sources, their evolution is not complete, and processes like minor (and likely dry) merging might still shape the structural properties of these objects to resemble those of their local counterparts, without substantially affecting their stellar mass or host stellar populations. Nonetheless, a definite conclusion on the actual relevance of size evolution for the studied early-type sample is precluded by possible systematics and biases. Show less
