Dipolar Dark Matter and Dark Energy

In previous work [L. Blanchet and A. Le Tiec, Phys. Rev. D 78, 024031 (2008)], a model of dark matter and dark energy based on the concept of gravitational polarization was investigated. This model was shown to recover the concordance cosmological scenario (Lambda-CDM) at cosmological scales, and the phenomenology of the modified Newtonian dynamics (MOND) at galactic scales. In this article we prove that the model can be formulated with a simple and physically meaningful matter action in general relativity. We also provide alternative derivations of the main results of the model, and some details on the variation of the action.Comment: 11 pages, 2 figures; minor stylistic corrections, added references, added appendix; to appear in Phys. Rev.

The Long Term Consequences of Specific Language Disabilities: The Secondary School Years

This research was directed toward the consequences of specific language disabilities on students during their secondary school years. The subjects were secondary students who had been identified as having the characteristics of specific language disabilities (SLD or developmental dyslexia) and who received remedial instruction while in elementary school. Remedial treatment utilized the Slingerland Adaptation of the Orton-Gillingham MultiSensory Approach to Language Arts with instruction given within regular education classrooms. These students were compared with a randomly selected cohort comparison group who were not known to have language learning problems. Major findings included: A higher percentage of the SLD group (81.4%) remained within the local school system than did the comparison group which had 72.1% of its subjects listed on local school records. School district data indicated that 91.6% of the listed SLD students and 88.9% of the listed comparison group students were currently active students. Academic success of the specific language disability group exceeded expectations. The majority of the SLD group were maintaining grade point averages and standardized achievement test scores within the average or above average range. Differences between the grade point averages of the SLD group and the comparison group were not significant. The standardized test scores of the SLD group remained significantly below those of the non-SLD comparison group. Above average stanine scores were achieved in reading by 24.9% of the SLD group. Another 51.9% of the SLD group maintained stanine scores in the average range. Little or no differences were observed between groups in regard to attitudes toward school, time spent on homework, participation in athletics or other extracurricular and peer group activities. Higher educational aspirations and vocational goals were similar for both groups. The researcher concluded that in spite of specific language disabilities the majority of these students were finding success during there secondary school years. This research provides strong support for the use of intervention programs with specific language disability students and the efficacy of the Slingerland Adaptation of the Orton-Gillingham MultiSensory Approach to Language Arts

The Complex Structure of the Multi-Phase Galactic Wind in a Starburst Merger

Neutral outflows have been detected in many ultraluminous infrared galaxies (ULIRGs) via the Na I D $\lambda\lambda 5890, 5896$ absorption-line doublet. For the first time, we have mapped and analyzed the 2-D kinematics of a cool neutral outflow in a ULIRG, F10565+2448, using the integral field unit (IFU) on Gemini North to observe the Na I D feature. At the same time we have mapped the ionized outflow with the [NII] and H$\alpha$ emission lines. We find a systemic rotation curve that is consistent with the rotation of the molecular disk determined from previous CO observations. The absorption lines show evidence of a nuclear outflow with a radial extent of at least 3 kpc, consistent with previous observations. The strength of the Na I D lines have a strong, spatially resolved correlation with reddening, suggesting that dust is present in the outflow. Surprisingly, the outflow velocities of the neutral gas show a strong asymmetry in the form of a major-axis gradient that is opposite in sign to disk rotation. This is inconsistent with entrained material rotating along with the galaxy or with a tilted minor-axis outflow. We hypothesize that this unusual behavior is due to an asymmetry in the distribution of the ambient gas. We also see evidence of asymmetric ionized outflow in the emission-line velocity map, which appear to be decoupled from the neutral outflow. Our results strengthen the hypothesis that ULIRG outflows differ in morphology from those in more quiescent disk galaxies.Comment: Accepted to Ap

No Evolution in the IR-Radio Relation for IR-Luminous Galaxies at z<2 in the COSMOS Field

Previous observational studies of the infrared (IR)-radio relation out to high redshift employed any detectable star forming systems at a given redshift within the restricted area of cosmological survey fields. Consequently, the evolution inferred relies on a comparison between the average IR/radio properties of (i) very IR-luminous high-z sources and (ii) more heterogeneous low(er)-z samples that often lack the strongest IR emitters. In this report we consider populations of objects with comparable luminosities over the last 10 Gyr by taking advantage of deep IR (esp. Spitzer 24 micron) and VLA 1.4 GHz observations of the COSMOS field. Consistent with recent model predictions, both Ultra Luminous Infrared Galaxies (ULIRGs) and galaxies on the bright end of the evolving IR luminosity function do not display any change in their average IR/radio ratios out to z~2 when corrected for bias. Uncorrected data suggested ~0.3 dex of positive evolution.Comment: 9 pages, 4 figures. Accepted for publication in ApJL

A Far-infrared Characterization of 24 μm Selected Galaxies at 0 < z < 2.5 using Stacking at 70 μm and 160 μm in the COSMOS Field

We present a study of the average properties of luminous infrared galaxies detected directly at 24 μm in the COSMOS field using a median stacking analysis at 70 μm and 160 μm. Over 35,000 sources spanning 0 ≤ z ≤ 3 and 0.06 mJy ≤ S_(24) ≤ 3.0 mJy are stacked, divided into bins of both photometric redshift and 24 μm flux. We find no correlation of S_(70)/S_(24) flux density ratio with S_(24), but find that galaxies with higher S_(24) have a lower S_(160)/S_(24) flux density ratio. These observed ratios suggest that 24 μm selected galaxies have warmer spectral energy distributions (SEDs) at higher mid-IR fluxes, and therefore have a possible higher fraction of active galactic nuclei. Comparisons of the average S_(70)/S_(24) and S_(160)/S_(24) colors with various empirical templates and theoretical models show that the galaxies detected at 24 μm are consistent with "normal" star-forming galaxies and warm mid-IR galaxies such as Mrk 231, but inconsistent with heavily obscured galaxies such as Arp 220. We perform a χ^2 analysis to determine best-fit galactic model SEDs and total IR luminosities for each of our bins. We compare our results to previous methods of estimating L IR and find that previous methods show considerable agreement over the full redshift range, except for the brightest S_(24) sources, where they overpredict the bolometric IR luminosity at high redshift, most likely due to their warmer dust SED. We present a table that can be used as a more accurate and robust method for estimating bolometric infrared luminosity from 24 μm flux densities

The Comoving Infrared Luminosity Density: Domination of Cold Galaxies across 0<z<1

In this paper we examine the contribution of galaxies with different infrared (IR) spectral energy distributions (SEDs) to the comoving infrared luminosity density, a proxy for the comoving star formation rate (SFR) density. We characterise galaxies as having either a cold or hot IR SED depending upon whether the rest-frame wavelength of their peak IR energy output is above or below 90um. Our work is based on a far-IR selected sample both in the local Universe and at high redshift, the former consisting of IRAS 60um-selected galaxies at z<0.07 and the latter of Spitzer 70um selected galaxies across 0.1<z<1. We find that the total IR luminosity densities for each redshift/luminosity bin agree well with results derived from other deep mid/far-IR surveys. At z<0.07 we observe the previously known results: that moderate luminosity galaxies (L_IR<10^11 Lsun) dominate the total luminosity density and that the fraction of cold galaxies decreases with increasing luminosity, becoming negligible at the highest luminosities. Conversely, above z=0.1 we find that luminous IR galaxies (L_IR>10^11 Lsun), the majority of which are cold, dominate the IR luminosity density. We therefore infer that cold galaxies dominate the IR luminosity density across the whole 0<z<1 range, hence appear to be the main driver behind the increase in SFR density up to z~1 whereas local luminous galaxies are not, on the whole, representative of the high redshift population.Comment: 5 pages, 3 figures, accepted for publication in MNRA

Mobilités et jeux d'échelle : de l'observation à l'analyse des flux dans la métropole parisienne.

Texte d'une communication présentée au colloque Géopoint 2010 (groupe Dupont, Université d'Avignon). Site web : http://www.groupe-dupont.org/ColloqueGeopoint/geopoint10.htmNational audienceThe spread of technological advances during the 20th century has transformed cities significantly. The inhabitants' spatial distribution is more decentralized and the cities' spatial organisation and functioning are more complex. Commuting flows are denser and more diversified. The purpose is to elaborate a general representation of commuting flows which allow showing their principal organisation trends while being coherent with the city's functional principles regarding the distribution of residential places, of working places and of commuting between them. The communes (finest level where the commuting flows are available), by virtue of their semantic variety in particular, do not respond to this double demand. Then, the objective is to identify relevant spatial entities and the levels at which they operate. Scales and ranges of the commuting flows linking these entities together and with their environment will then be estimated. At last, the co-existence of different models of modal choice according to the form of the attractions will be shown.La diffusion des progrès technologiques au cours du vingtième siècle a transformé les villes de façon considérable. La distribution spatiale des habitants a suivi un mouvement général de déconcentration et l'organisation spatiale de la métropole et son fonctionnement se sont complexifiés. Les flux de déplacements quotidiens sont plus denses et plus diversifiés. L'enjeu consiste à construire une représentation généralisée des déplacements domicile-travail dans la métropole francilienne qui rend visible les principales régularités structurant leur organisation tout en étant en cohérence avec les logiques fonctionnelles de l'espace métropolitain en termes de distribution des lieux de résidence et d'emploi et des déplacements entre eux. Les communes (niveau le plus fin auquel les données sont disponibles), de par leur variété sémantique notamment, ne répondent pas à cette double exigence. Il s'agit alors d'identifier des entités spatiales pertinentes et les niveaux auxquels elles opèrent. On évaluera ensuite les échelles et portées correspondant aux flux de déplacement liant ces entités entre elles et à leur environnement, définissant une partition de l'espace étudié. Enfin, on montrera la co-existence de différents modèles de distributions modales en fonction de la nature des polarisations

Children With Persistent Feeding Difficulties: An Observational Analysis of the Feeding Interactions of Problem and Non-Problem Eaters

This study examined the relationship between parent's feeding practices and the feeding behavior of toddlers and preschool-age children with (n = 19) or without (n = 26) persistent feeding difficulties. Specifically, patterns of parent-child interaction were assessed during standardized family mealtime observations in the clinic. Parents also kept observational records of their children's mealtime behavior at home and rated the degree of difficulty they experienced in feeding their child during each meal on a daily basis. Observational results showed that feeding-disordered children engaged in higher levels of disruptive mealtime behavior (food refusal, noncompliance, complaining, oppositional behavior, and playing with food) and lower levels of chewing during mealtime. There were several significant age effects, with younger children (under age 3) engaging in more vomiting and less aversive demanding and verbalizations. Parents of feeding-disordered children were more negative and coercive in their feeding practices and engaged in higher levels of aversive instruction giving, aversive prompting, and negative eating-related comments. There were several significant associations between coercive parental behaviors and children's food refusal and noncompliance in the sample as a whole. Measures of children's disruptiveness at mealtimes in the clinic were significantly correlated with measures of mealtime behavior in the home