Likelihood Analysis of Cosmic Shear on Simulated and VIRMOS-DESCART Data

We present a maximum likelihood analysis of cosmological parameters from measurements of the aperture mass up to 35 arcmin, using simulated and real cosmic shear data. A four-dimensional parameter space is explored which examines the mean density \Omega_M, the mass power spectrum normalization \sigma_8, the shape parameter \Gamma and the redshift of the sources z_s. Constraints on \Omega_M and \sigma_8 (resp. \Gamma and z_s) are then given by marginalizing over \Gamma and z_s (resp. \Omega_M and \sigma_8). For a flat LCDM cosmologies, using a photometric redshift prior for the sources and \Gamma \in [0.1,0.4], we find \sigma_8=(0.57\pm0.04) \Omega_M^{(0.24\mp 0.18) \Omega_M-0.49} at the 68% confidence level (the error budget includes statistical noise, full cosmic variance and residual systematic). The estimate of \Gamma, marginalized over \Omega_M \in [0.1,0.4], \sigma_8 \in [0.7,1.3] and z_s constrained by photometric redshifts, gives \Gamma=0.25\pm 0.13 at 68% confidence. Adopting h=0.7, a flat universe, \Gamma=0.2 and \Omega_m=0.3 we find \sigma_8=0.98 \pm0.06 . Combined with CMB, our results suggest a non-zero cosmological constant and provide tight constraints on \Omega_M and \sigma_8. We finaly compare our results to the cluster abundance ones, and discuss the possible discrepancy with the latest determinations of the cluster method. In particular we point out the actual limitations of the mass power spectrum prediction in the non-linear regime, and the importance for its improvement.Comment: 11 pages, submitted to A&

Spectroscopic follow up of arclets in AC114 with the VLT

We present the first results on the VLT/FORS-1 spectroscopic survey of amplified sources and multiple images in the lensing cluster AC114. Background sources were selected in the cluster core, close to the critical lines, using photometric redshifts combined with lensing inversion criteria. Spectroscopic results are given, together with a brief summary of the properties of some of these high-z galaxies.Comment: 4pages. To appear in the Proceedings of the XXth Moriond Astrophysics Meeting "Cosmological Physics with Gravitational Lensing", eds. J.-P. Kneib, Y. Mellier, M. Moniez and J. Tran Thanh Van, Les Arcs, France, March 11th-18th 200

Fullerene-assisted electron-beam lithography for pattern improvement and loss reduction in InP membrane waveguide devices

In this Letter, we present a method to prepare a mixed electron-beam resist composed of a positive resist (ZEP520A) and C 60 fullerene. The addition of C 60 to the ZEP resist changes the material properties under electron beam exposure significantly. An improvement in the thermal resistance of the mixed material has been demonstrated by fabricating multimode interference couplers and coupling regions of microring resonators. The fabrication of distributed Bragg reflector structures has shown improvement in terms of pattern definition accuracy with respect to the same structures fabricated with normal ZEP resist. Straight InP membrane waveguides with different lengths have been fabricated using this mixed resist. A decrease of the propagation loss from 6.6 to 3.3¿¿dB/cm has been demonstrated

LRG J0239-0134: A Ring Galaxy or a Pair of Superbubbles at z=1 ?

The unusual morphology of LRG J0239$-$0134 at $z$ =1.062 has been interpreted as a ring galaxy. Here we propose an alternative idea that the ring-like morphology is attributed to a pair of superbubbles driven by the intense starburst in the central region of this galaxy. Supporting evidence for a superbubble model is; 1) the poststarburst nature in the central body suggests that a burst of supernova explosions could occur at least $\sim 10^7$ yr ago, 2) the dark lane seen in the central body suggests that we observe this object from a nearly edge-on view, and, 3) the ring-like morphology is not inconsistent with an idea that it is a pair of superbubbles. All these pieces of evidence for the superbubble model seem circumstantial. However, if this is the case, this galaxy provides an important example of the superwind activity at high redshift.Comment: 5 pages (3 ps files are included) [emulateapj]. The Astrophysical Journal (Letters), in pres