A 12 μm ISOCAM survey of the ESO-Sculptor field

We present a detailed reduction of a mid-infrared 12 μm (LW10 filter) ISOCAM open time observation performed on the ESOSculptor Survey field (Arnouts et al. 1997, A&AS, 124, 163). A complete catalogue of 142 sources (120 galaxies and 22 stars), detected with high significance (equivalent to 5σ), is presented above an integrated flux density of 0.24 mJy. Star/galaxy separation is performed by a detailed study of colour-colour diagrams. The catalogue is complete to 1 mJy and, below this flux density, the incompleteness is corrected using two independent methods. The first method uses stars and the second uses optical counterparts of the ISOCAM galaxies; these methods yield consistent results. We also apply an empirical flux density calibration using stars in the field. For each star, the 12 μm flux density is derived by fitting optical colours from a multi-band χ^2 to stellar templates (BaSel-2.0) and using empirical optical-IR colour-colour relations. This article is a companion analysis to our 2007 paper (Rocca-Volmerange et al. 2007, A&A, 475, 801) where the 12 μm faint galaxy counts are presented and analysed per galaxy type with the evolutionary code PÉGASE.3

The 2-point angular correlation function of 20,000 galaxies to V<23.5 and I<22

The UH8K wide field camera of the CFHT was used to image 0.68 deg^2 of sky. From these images, ~20,000 galaxies were detected to completeness magnitudes V<23.5 and I<22.5. The angular correlation function of these galaxies is well represented by the parameterization omega(theta) = A_W*theta^-delta. The slope delta=-0.8 shows no significant variation over the range of magnitude. The amplitude A_W decreases with increasing magnitude in a way that is most compatible with a Lambda-CDM model (Omega_0 = 0.2, Lambda=0.8) with a hierarchical clustering evolution parameter epsilon>0. We infer a best-fit spatial correlation length of r_00= 5.85+/-0.5 h^-1 Mpc at z=0. The peak redshift of the survey (I<22.5) is estimated to be z_peak~0.58, using the blue-evolving luminosity function from the CFRS and the flat Lambda cosmology, and r_0(z_peak)=3.5+/-0.5 h^-1 Mpc. We also detect a significant difference in clustering amplitude for the red and blue galaxies, quantitatively measured by correlation lengths of r_00=5.3+/-0.5 h^-1 Mpc and r_00=1.9+/-0.9 h^-1 Mpc respectively, at z=0.Comment: 21 pages, 21 figures,accepted in Astronomy and Astrophysic

Déplacements domicile-travail en Île-de-France et choix individuels du mode de transport

Nous étudions dans cet article le choix du mode de transport pour un déplacement domicile-travail au sein de la région Île-de-France dans un ensemble à deux modalités : véhicule particulier ou transports en commun. Nous modélisons la présence d’effets indirects liés aux autres dimensions de la demande de transport et l’existence d’hétérogénéité des goûts dans la population observée. Nous spécifions, identifions et estimons par la méthode du maximum de vraisemblance simulée un modèle Logit à paramètres aléatoires. Les résultats sont nombreux et réalistes : dispersion des goûts concernant les attributs de transports et les variables socio-économiques, corrélation positive entre valeur du temps et niveau de la congestion, rejet de l’axiome IIA.We develop in this paper a dichotomous discrete choice model for the analysis of home to work trips in the French Parisian region. The two modes of transportation are private motorized vehicle and public transportation. We analyse indirect effects coming from the other choices associated with the demand for travel. We also take into account random tastes of travellers. A mixed Logit model is formulated. Identification of the parameters and estimation by maximization of the simulated likelihood function are discussed. The results of the application are realistic and intuitive: tastes for travel attributes are heterogeneous among the population, so are the effects of their socioeconomic variables, the correlation of the value of time with the level of road congestion is positive and the IIA axiom does not hold

Addiction to car use and dynamic elasticity measures in France

This article presents a microeconometric analysis of the annual mileage travelled by French households with their personal cars, defining their automobility. To feature car use dependence, the rational addiction model of Becker et al. (1994) is applied on a panel dataset, drawn from the French "Car Fleet" survey over the period 1999-2001. Importantly, the estimates show that the assumption of addiction to car use cannot be rejected. Furthermore, the model yields realistic kilometric-price and income elasticities of household automobility, for both the short and the long runs.Transportation ; Car use ; Consumption ; Addiction ; Panel ; GMM

The ESO-Sculptor Survey: Luminosity functions of galaxies per spectral type at redshifts 0.1-0.5

[ABRIDGED] We present the first statistical analysis of the complete ESO-Sculptor redshift survey (ESS). The flux-calibrated sample of 617 galaxy spectra with R_c<20.5 is separated into 3 spectral classes (early, intermediate, and late). We report in detail on the spectral classification, the polynomial K-corrections, and all sources of corresponding random and systematic errors. The derived luminosity functions (LF) in the Johnson-Cousins B and Rc bands are in agreement with the results from the comparable CNOC2 survey (Lin et al. 1999), whereas the ESS provides the first estimates of LFs per spectral type in the Johnson V band. A renewed interpretation of the galaxy LFs from a redshift survey are obtained by fitting the ESS LFs with composite functions based on the local LFs per morphological type (Sandage, Binggeli & Tammann 1985; Jerjen & Tammann 1997). As good or better fits than with pure Schechter functions are obtained using: for the early-type LF, a two-wing Gaussian; for the intermediate-type LF, the sum of a Gaussian modeling the Spiral galaxies and a steep Schechter function (alpha=-1.5) representing the dwarf elliptical galaxies; for the late-type LF, a similar composite function with a flat or weaker slope (-0.8<alpha<-0.3) for the Schechter component which represents the dwarf Irregular galaxies. This analysis illustrates how LFs per spectral type may be affected by morphological type mixing, and emphasizes the need for a quantitative morphological classification at z>0.1 which separates the giant and dwarf galaxy populations.Comment: 33 Pages, 13 color figures, A&A Latex macro. Published in A&

Examining visual cues for an auditory selective attention paradigm in virtual reality

Over the last few years, virtual reality (VR) has emerged as a new technology that is allowing scientific research to investigate topics from another perspective. This is due to the possibility of creating more realistic scenarios in which all the variables are controlled. Thus, the conclusions taken from such research are more consistent since the environment can be much more controlled than without using VR. This thesis researched and validated a new visual cue in an experiment on auditory selective attention (ASA) experiment in virtual reality. The aim was to see how including a visual cue that participants had to search for affected their ASA, which would be a more realistic situation in a class scenario. In an already validated VR environment, changes were made to fit the purpose of this project. Four avatars were situated in four different directions in a classroom (front, left, back and right). One of the four avatars would clap at every trial, which would indicate the direction from which the auditory stimulus would later come from, and the participant had to search for it. When they did, they had to press a button, and then auditory stimuli coming from the avatar's direction would play. Another stimulus would play simultaneously from another direction to act as a distractor. Participants had then to indicate a characteristic of the target stimulus. To see how the participants' strategy worked in this new environment, the time it took to find the cue and the head tracking of the headset were saved during the experiment. The experiment was done with 10 participants. The experiment worked and proved that not all participants had the same strategy when searching for the cue. Participants would look at the cue for the front and sides positions when hearing the auditory stimulus. Whereas for the back cue, participants, when detecting that the avatar on the back was the one clapping, the participants would put themselves in a more comfortable position looking at the front to hear the auditory stimuli. Most participants' results were in a similar range, but there were different outcomes for two participants. One of them suffered cybersickness, and the other participant looked closer to the frontal position than any other participant.En los últimos años, la realidad virtual (RV) ha surgido como una nueva tecnología que está permitiendo a la investigación científica indagar temas desde otra perspectiva. Esto se debe a la posibilidad de crear escenarios más realistas en los que se controlan todas las variables. De este modo, las conclusiones que se obtienen de estas investigaciones son más consistentes, ya que el entorno puede estar mucho más controlado que si no se utiliza la RV. En esta tesis se investigó y se validó una nueva pista visual en un experimento de atención selectiva auditiva (ASA) en realidad virtual. El objetivo era ver cómo la inclusión de una pista visual que los participantes tenían que buscar afectaba a su ASA, se quería obtener una situación más realista en un escenario de clase. En un entorno de RV ya validado, se introdujeron cambios para adaptarlo al propósito de este proyecto. Se situaron cuatro avatares en cuatro direcciones diferentes de un aula (delante, izquierda, detrás y derecha). Uno de los cuatro avatares aplaudía en cada ensayo, lo que indicaba la dirección de la que provendría posteriormente el estímulo auditivo, y el participante tenía que buscarlo. Cuando lo hacían, tenían que pulsar un botón, y entonces sonaban los estímulos auditivos procedentes de la dirección del avatar. Simultáneamente, se reproducía otro estímulo procedente de otra dirección para que sirviera de distractor. A continuación, los participantes tenían que indicar una característica del estímulo objetivo. Para ver cómo funcionaba la estrategia de los participantes en este nuevo entorno, se guardó durante el experimento el tiempo que tardaban en encontrar la pista y el seguimiento del casco de RV. El experimento se realizó con 10 participantes. El experimento funcionó y demostró que no todos los participantes tenían la misma estrategia a la hora de buscar la pista. Los participantes buscaban la pista para las posiciones delantera y lateral cuando escuchaban el estímulo auditivo. Mientras que para la pista de detrás, los participantes, al detectar que el avatar de detrás era el que aplaudía, se ponían en una posición más cómoda mirando al frente para escuchar los estímulos auditivos. Los resultados de la mayoría de los participantes estaban en un rango similar, pero hubo resultados diferentes para dos participantes. Uno de ellos sufrió ciberenfermedad, y el otro participante miró más cerca de la posición frontal que cualquier otro participante.En els darrers anys, la realitat virtual (RV) ha sorgit com una nova tecnologia que permet a la recerca científica indagar temes des d'una altra perspectiva. Això és degut a la possibilitat de crear escenaris més realistes on es controlen totes les variables. D'aquesta manera, les conclusions que s'obtenen d'aquestes investigacions són més consistents, ja que l'entorn pot estar molt més controlat que si no es fa servir la RV. En aquesta tesi es va investigar i es va validar una pista visual nova en un experiment d'atenció selectiva auditiva (ASA) en realitat virtual. L'objectiu era veure com la inclusió d'una pista visual que els participants havien de buscar afectava la seva ASA, es volia obtenir una situació més realista en un escenari de classe. En un entorn de RV ja validat, s'han introduït canvis per adaptar-lo al propòsit d'aquest projecte. Es van situar quatre avatars en quatre direccions diferents d'una aula (davant, esquerra, darrera i dreta). Un dels quatre avatars aplaudia a cada assaig, cosa que indicava la direcció de la qual provenia posteriorment l'estímul auditiu, i el participant havia de buscar-lo. Quan ho feien, havien de prémer un botó, i aleshores sonaven els estímuls auditius procedents de la direcció de l'avatar. Simultàniament, es reproduïa un altre estímul procedent d'una altra adreça perquè servís de distractor. Tot seguit, els participants havien d'indicar una característica de l'estímul objectiu. Per veure com funcionava l'estratègia dels participants en aquest nou entorn, durant l'experiment es va guardar el temps que trigaven a trobar la pista i el seguiment del casc de RV. L'experiment es va fer amb 10 participants. L'experiment va funcionar i va demostrar que tots els participants no tenien la mateixa estratègia a l'hora de buscar la pista. Els participants buscaven la pista per a les posicions davanteres i laterals quan escoltaven l'estímul auditiu. Mentre que per a la pista de darrera, els participants, en detectar que l'avatar de darrera era el que aplaudia, es posaven en una posició més còmoda mirant endavant per escoltar els estímuls auditius. Els resultats de la majoria dels participants estaven en un rang similar, però va haver-hi resultats diferents per a dos participants. Un va patir cibermalaltia, i l'altre participant va mirar més a prop de la posició frontal que qualsevol altre participant