Giant Anisotropy of Spin-Orbit Splitting at the Bismuth Surface

We investigate the bismuth (111) surface by means of time and angle resolved photoelectron spectroscopy. The parallel detection of the surface states below and above the Fermi level reveals a giant anisotropy of the Spin-Orbit (SO) spitting. These strong deviations from the Rashba-like coupling cannot be treated in $\textbf{k}\cdot \textbf{p}$ perturbation theory. Instead, first principle calculations could accurately reproduce the experimental dispersion of the electronic states. Our analysis shows that the giant anisotropy of the SO splitting is due to a large out-of plane buckling of the spin and orbital texture.Comment: 5 pages, 4 figure

The VIMOS VLT Deep Survey - Evolution of the luminosity functions by galaxy type up to z=1.5 from first epoch data

From the first epoch observations of the VVDS up to z=1.5 we have derived luminosity functions (LF) of different spectral type galaxies. The VVDS data, covering ~70% of the life of the Universe, allow for the first time to study from the same sample and with good statistical accuracy the evolution of the LFs by galaxy type in several rest frame bands from a purely magnitude selected sample. The magnitude limit of the VVDS allows the determination of the faint end slope of the LF with unprecedented accuracy. Galaxies have been classified in four spectral classes, using their colours and redshift, and LFs have been derived in the U, B, V, R and I rest frame bands from z=0.05 to z=1.5. We find a significant steepening of the LF going from early to late types. The M* parameter is significantly fainter for late type galaxies and this difference increases in the redder bands. Within each of the galaxy spectral types we find a brightening of M* with increasing redshift, ranging from =< 0.5 mag for early type galaxies to ~1 mag for the latest type galaxies, while the slope of the LF of each spectral type is consistent with being constant with redshift. The LF of early type galaxies is consistent with passive evolution up to z~1.1, while the number of bright early type galaxies has decreased by ~40% from z~0.3 to z~1.1. We also find a strong evolution in the normalization of the LF of latest type galaxies, with an increase of more than a factor 2 from z~0.3 to z~1.3: the density of bright late type galaxies in the same redshift range increases of a factor ~6.6. These results indicate a strong type-dependent evolution and identifies the latest spectral types as responsible for most of the evolution of the UV-optical luminosity function out to z=1.5.Comment: 18 pages with encapsulated figures, revised version after referee's comments, accepted for publication in A&

Isoscaling and the symmetry energy in spectator fragmentation

Isoscaling and its relation to the symmetry energy in the fragmentation of excited residues produced at relativistic energies were studied in two experiments conducted at the GSI laboratory. The INDRA multidetector has been used to detect and identify light particles and fragments with Z <= 5 in collisions of 12C on 112,124Sn at incident energies of 300 and 600 MeV per nucleon. Isoscaling is observed, and the deduced parameters decrease with increasing centrality. Symmetry term coefficients, deduced within the statistical description of isotopic scaling, are near gamma = 25 MeV for peripheral and gamma < 15 MeV for central collisions. In a very recent experiment with the ALADIN spectrometer, the possibility of using secondary beams for reaction studies at relativistic energies has been explored. Beams of 107Sn, 124Sn, 124La, and 197Au were used to investigate the mass and isospin dependence of projectile fragmentation at 600 MeV per nucleon. The decrease of the isoscaling parameters is confirmed and extended over the full fragmentation regime covered in these reactions.Comment: Proceedings of the IWM2005, Catania, Italy, Nov 200

A wide-field spectroscopic survey of the cluster of galaxies Cl0024+1654: I. The catalogue

We present the catalogue of a wide-field CFHT/WHT spectroscopic survey of the lensing cluster Cl0024+1654 at z=0.395. This catalogue contains 618 new spectra, of which 581 have identified redshifts. Adding redshifts available from the literature, the final catalogue contains data for 687 objects with redshifts identified for 650 of them. 295 galaxies have redshifts in the range 0.37<z<0.41, i. e. are cluster members or lie in the immediate neighbourhood of the cluster. The area covered by the survey is 21x25 arcmin2 in size, corresponding to 4x4.8 h^-2 Mpc2 at the cluster redshift. The survey is 45% complete down to V=22 over the whole field covered; within 3 arcmin of the cluster centre the completeness exceeds 80% at the same magnitude. A detailed completeness analysis is presented. The catalogue gives astrometric position, redshift, V magnitude and V-I colour, as well as the equivalent widths for a number of lines. Apart from the cluster Cl0024+1654 itself, three other structures are identified in redshift space: a group of galaxies at z=0.38, just in front of Cl0024+1654 and probably interacting with it, a close pair of groups of galaxies at z~0.495 and an overdensity of galaxies at z~0.18 with no obvious centre. The spectroscopic catalogue will be used to trace the three-dimensional structure of the cluster Cl0024+1654 as well as study the physical properties of the galaxies in the cluster and in its environment.Comment: 14 pages - figures included - A&A (re)submitted versio

The XMM-LSS Survey: A well controlled X-ray cluster sample over the D1 CFHTLS area

We present the XMM-LSS cluster catalogue corresponding to the CFHTLS D1 area. The list contains 13 spectroscopically confirmed, X-ray selected galaxy clusters over 0.8 deg2 to a redshift of unity and so constitutes the highest density sample of clusters to date. Cluster X-ray bolometric luminosities range from 0.03 to 5x10^{44} erg/s. In this study, we describe our catalogue construction procedure: from the detection of X-ray cluster candidates to the compilation of a spectroscopically confirmed cluster sample with an explicit selection function. The procedure further provides basic X-ray products such as cluster temperature, flux and luminosity. We detected slightly more clusters with a (0.5-2.0 keV) X-ray fluxes of >2x10^{-14} erg/s/cm^{-2} than we expected based on expectations from deep ROSAT surveys. We also present the Luminosity-Temperature relation for our 9 brightest objects possessing a reliable temperature determination. The slope is in good agreement with the local relation, yet compatible with a luminosity enhancement for the 0.15 < z< 0.35 objects having 1 < T < 2 keV, a population that the XMM-LSS is identifying systematically for the first time. The present study permits the compilation of cluster samples from XMM images whose selection biases are understood. This allows, in addition to studies of large-scale structure, the systematic investigation of cluster scaling law evolution, especially for low mass X-ray groups which constitute the bulk of our observed cluster population. All cluster ancillary data (images, profiles, spectra) are made available in electronic form via the XMM-LSS cluster database.Comment: 12 pages 5 figures, MNRAS accepted. The paper with full resolution cluster images is available at http://vela.astro.ulg.ac.be/themes/spatial/xmm/LSS/rel_pub_e.htm

Transfer of spectral weight across the gap of Sr2IrO4 induced by La doping

We study with Angle Resolved PhotoElectron Spectroscopy (ARPES) the evolution of the electronic structure of Sr2IrO4, when holes or electrons are introduced, through Rh or La substitutions. At low dopings, the added carriers occupy the first available states, at bottom or top of the gap, revealing an anisotropic gap of 0.7eV in good agreement with STM measurements. At further doping, we observe a reduction of the gap and a transfer of spectral weight across the gap, although the quasiparticle weight remains very small. We discuss the origin of the in-gap spectral weight as a local distribution of gap values

Accurate photometric redshifts for the CFHT Legacy Survey calibrated using the VIMOS VLT Deep Survey

We present photometric redshifts for an uniquely large and deep sample of 522286 objects with i'_{AB}<25 in the Canada-France Legacy Survey ``Deep Survey'' fields, which cover a total effective area of 3.2 deg^2. We use 3241 spectroscopic redshifts with 0<z<5 from the VIMOS VLT Deep Survey as a calibration to derive these photometric redshifts. We devise a robust calibration method which removes systematic trends in the photometric redshifts and significantly reduces the fraction of catastrophic errors. We use our unique spectroscopic sample to present a detailed assessment of the robustness of the photometric redshift sample. For a sample selected at i'_{AB}<24, we reach a redshift accuracy of \sigma_{\Delta z/(1+z)}=0.037 with \eta=3.7% of catastrophic error. The reliability of our photometric redshifts is lower for fainter objects: we find \sigma_{\Delta z/(1+z)}=0.029, 0.043 and \eta=1.7%, 5.4% for samples selected at i'_{AB}=17.5-22.5 and 22.5-24 respectively. We find that the photometric redshifts of starburst galaxies in our sample are less reliable: although these galaxies represent only 18% of the spectroscopic sample they are responsible for 54% of the catastrophic errors. We find an excellent agreement between the photometric and the VVDS spectroscopic redshift distributions at i'_{AB}<24. Finally, we compare the redshift distributions of i' selected galaxies on the four CFHTLS deep fields, showing that cosmic variance is already present on fields of 0.8 deg^2.Comment: 19 pages, 17 figures, submitted to A&A. The photometric redshifts described in this paper will be made publicly available from 1st may 2006 at http://terapix.iap.fr and http://cencosw.oamp.fr

The Star Formation Rate Density and Dust Attenuation Evolution over 12 Gyr with the VVDS Surveys

[Abridged] We investigate the global galaxy evolution over 12 Gyr (0.05<z<4.5), from the star formation rate density (SFRD), combining the VVDS Deep (17.5<=I<=24.0) and Ultra-Deep (23.00<=i<=24.75) surveys. We obtain a single homogeneous spectroscopic redshift sample, totalizing about 11000 galaxies. We estimate the rest-frame FUV luminosity function (LF) and luminosity density (LD), extract the dust attenuation of the FUV radiation using SED fitting, and derive the dust-corrected SFRD. We find a constant and flat faint-end slope alpha in the FUV LF at z1.7, we set alpha steepening with (1+z). The absolute magnitude M*_FUV brightens in the entire range 02 it is on average brighter than in the literature, while phi* is smaller. Our total LD shows a peak at z=2, present also when considering all sources of uncertainty. The SFRD history peaks as well at z=2. It rises by a factor of 6 during 2 Gyr (from z=4.5 to z=2), and then decreases by a factor of 12 during 10 Gyr down to z=0.05. This peak is mainly produced by a similar peak within the population of galaxies with -21.5<=M_FUV<=-19.5 mag. As times goes by, the total SFRD is dominated by fainter and fainter galaxies. The presence of a clear peak at z=2 and a fast rise at z>2 of the SFRD is compelling for models of galaxy formation. The mean dust attenuation A_FUV of the global galaxy population rises by 1 mag during 2 Gyr from z=4.5 to z=2, reaches its maximum at z=1 (A_FUV=2.2 mag), and then decreases by 1.1 mag during 7 Gyr down to z=0. The dust attenuation maximum is reached 2 Gyr after the SFRD peak, implying a contribution from the intermediate-mass stars to the dust production at z<2.Comment: 23 pages, 15 figures, accepted for publication in A&