Infrared Properties of the Halo, Bulge and Disk of the Edge-On Galaxy NGC 7814

Highly resolved images of the edge-on galaxy NGC 7814 from 2MASS and Spitzer were used to extract the morphologies and spectral energy distributions (SEDs) of the disk, bulge and halo components of this galaxy over a wavelength range from 1.25 to 24 μm. This represents the first direct determination of the mid-infrared emission of the bulge and halo components of a galaxy other than the Milky Way. The SEDs of all three structures imply the presence of emission components from direct stellar light and from at least one further component. For the disk, this further component is interpreted as dust emission having properties typical of star forming disks. The emission from the bulge and the halo is very significantly in excess of that from an extrapolation of the near infrared emission from stars. This excess has a flat spectrum between 8 and 24 μm bands and has an unknown origin. I discuss potential explanations such as dust emission in an interstellar medium, galactic winds, star forming regions and circumstellar dust, as well as emission from brown dwarfs. Further analysis is needed to test these hypotheses

The Infrared Luminosity of Galaxy Clusters

The aim of this study is to quantify the infrared luminosity of clusters as a function of redshift and compare this with the X-ray luminosity. This can potentially constrain the origin of the infrared emission to be intracluster dust and/or dust heated by star formation in the cluster galaxies. We perform a statistical analysis of a large sample of galaxy clusters selected from existing databases and catalogues.We coadd the infrared IRAS and X-ray RASS images in the direction of the selected clusters within successive redshift intervals up to z = 1. We find that the total infrared luminosity is very high and on average 20 times higher than the X-ray luminosity. If all the infrared luminosity is to be attributed to emission from diffuse intracluster dust, then the IR to X-ray ratio implies a dust-to-gas mass abundance of 5e-4. However, the infrared luminosity shows a strong enhancement for 0.1 < z < 1, which cannot be attributed to cluster selection effects. We show that this enhancement is compatible with a star formation rate in the member galaxies that is typical of the central Mpc of the Coma cluster at z = 0 and evolves with the redshift as (1+z)^5. It is likely that most of the infrared luminosity that we measure is generated by the ongoing star formation in the member galaxies. From theoretical predictions calibrated on extinction measurements (dust mass abundance equal to 1e-5), we expect only a minor contribution, of a few percent, from intracluster dust.Comment: 9 pages, 7 figures, accepted july 31st 2008 for publication in Astronomy and Astrophysics, language improved for this versio

Galaxy and mass assembly (GAMA): dust obscuration in galaxies and their recent star formation histories

We present self-consistent star formation rates derived through pan-spectral analysis of galaxies drawn from the Galaxy and Mass Assembly (GAMA) survey. We determine the most appropriate form of dust obscuration correction via application of a range of extinction laws drawn from the literature as applied to Hα, [O ii] and UV luminosities. These corrections are applied to a sample of 31 508 galaxies from the GAMA survey at z < 0.35. We consider several different obscuration curves, including those of Milky Way, Calzetti and Fischera & Dopita curves and their effects on the observed luminosities. At the core of this technique is the observed Balmer decrement, and we provide a prescription to apply optimal obscuration corrections using the Balmer decrement. We carry out an analysis of the star formation history (SFH) using stellar population synthesis tools to investigate the evolutionary history of our sample of galaxies as well as to understand the effects of variation in the initial mass function (IMF) and the effects this has on the evolutionary history of galaxies. We find that the Fischera & Dopita obscuration curve with an Rv value of 4.5 gives the best agreement between the different SFR indicators. The 2200 Å feature needed to be removed from this curve to obtain complete consistency between all SFR indicators suggesting that this feature may not be common in the average integrated attenuation of galaxy emission. We also find that the UV dust obscuration is strongly dependent on the SF

Peer substance use overestimation among French university students: a cross-sectional survey

<p>Abstract</p> <p>Background</p> <p>Normative misperceptions have been widely documented for alcohol use among U.S. college students. There is less research on other substances or European cultural contexts. This study explores which factors are associated with alcohol, tobacco and cannabis use misperceptions among French college students, focusing on substance use.</p> <p>Methods</p> <p>12 classes of second-year college students (n = 731) in sociology, medicine, nursing or foreign language estimated the proportion of tobacco, cannabis, alcohol use and heavy episodic drinking among their peers and reported their own use.</p> <p>Results</p> <p>Peer substance use overestimation frequency was 84% for tobacco, 55% for cannabis, 37% for alcohol and 56% for heavy episodic drinking. Cannabis users (p = 0.006), alcohol (p = 0.003) and heavy episodic drinkers (p = 0.002), are more likely to overestimate the prevalence of use of these consumptions. Tobacco users are less likely to overestimate peer prevalence of smoking (p = 0.044). Women are more likely to overestimate tobacco (p < 0.001) and heavy episodic drinking (p = 0.007) prevalence. Students having already completed another substance use questionnaire were more likely to overestimate alcohol use prevalence (p = 0.012). Students exposed to cannabis prevention campaigns were more likely to overestimate cannabis (p = 0.018) and tobacco use (p = 0.022) prevalence. Other identified factors are class-level use prevalences and academic discipline.</p> <p>Conclusions</p> <p>Local interventions that focus on creating realistic perceptions of substance use prevalence could be considered for cannabis and alcohol prevention in French campuses.</p

Grossesse et polyconsommations de substances psychoactives : modifications de la clientèle et des prises en charge, 1999-2008

Les changements dans les consommations de substances psychoactives en France depuis dix ans sont repérables chez les femmes enceintes. L'étude rétrospective d'une cohorte de 170 nouveau-nés dont la mère consommait au moins deux substances a permis de rassembler des données sur les consommations des mères et leurs prises en charge

Conséquences, pour l’enfant à naître, du maintien de la consommation d’alcool pendant la grossesse

International audienc

: Consequences for the newborn of alcohol consumption during pregnancy

International audienceThis paper aims at showing the immediate and longterm consequences affecting newborns whose mothers did not reduce or stop their consumption of alcohol when they were pregnant; these women were chosen among women who also used psychoactive substances. A retrospective cohort was constituted of babies who were found to have been exposed in utero to one or more legal or illegal psychoactive substance(s) and who were born or hospitalized between 1999 and 2008 in a hospital near Paris. Among the cohort of 170 babies, 56 had mothers who had not modified their alcohol consumption when they were pregnant, 30 had mothers who had reduced their alcohol consumption, and 84 had mothers who declared having been abstinentUne cohorte rétrospective a été reconstituée par le repérage des enfants exposés in utero à une ou plusieurs substances psychoactives licites ou illicites, nés ou hospitalisés entre 1999 et 2008 dans un hôpital de la région parisienne. Sur les 170 nouveau-nés de mères de cette cohorte, 56 avaient une mère consommatrice inchangée d'alcool pendant toute sa grossesse, 30 avaient une mère dont la consommation s'était réduite, et 84 avaient une mère s'étant déclarée abstinente à l'alcool. Les nouveau-nés de mères consommatrices inchangées d'alcool pendant la grossesse étaient davantage prématurés (30 %) et hospitalisés dans le service de néonatologie (60,7 %) auxquels il avait fallu apporter des soins spécifiques pour des durées significativement plus longues que les autres enfants exposés in utero aux autres substances psychoactives (p < 0,005). Ils étaient plus souvent porteurs des effets de l'alcoolisation foetale (18 %) et placés en famille d'accueil (18 %