Dense molecular globulettes and the dust arc towards the runaway O star AE Aur (HD 34078)

Some runaway stars are known to display IR arc-like structures around them, resulting from their interaction with surrounding interstellar material. The properties of these features as well as the processes involved in their formation are still poorly understood. We aim at understanding the physical mechanisms that shapes the dust arc observed near the runaway O star AEAur (HD34078). We obtained and analyzed a high spatial resolution map of the CO(1-0) emission that is centered on HD34078, and that combines data from both the IRAM interferometer and 30m single-dish antenna. The line of sight towards HD34078 intersects the outer part of one of the detected globulettes, which accounts for both the properties of diffuse UV light observed in the field and the numerous molecular absorption lines detected in HD34078's spectra, including those from highly excited H2 . Their modeled distance from the star is compatible with the fact that they lie on the 3D paraboloid which fits the arc detected in the 24 {\mu}m Spitzer image. Four other compact CO globulettes are detected in the mapped area. These globulettes have a high density and linewidth, and are strongly pressure-confined or transient. The good spatial correlation between the CO globulettes and the IR arc suggests that they result from the interaction of the radiation and wind emitted by HD 34078 with the ambient gas. However, the details of this interaction remain unclear. A wind mass loss rate significantly larger than the value inferred from UV lines is favored by the large IR arc size, but does not easily explain the low velocity of the CO globulettes. The effect of radiation pressure on dust grains also meets several issues in explaining the observations. Further observational and theoretical work is needed to fully elucidate the processes shaping the gas and dust in bow shocks around runaway O stars. (Abridged)Comment: Accepted for publication in Astronomy & Astrophysic

Interstellar H2 toward HD 37903

We present an analysis of interstellar H2 toward HD 37903, which is a hot, B 1.5 V star located in the NGC 2023 reflection nebula. Meyer et al. (2001) have used a rich spectrum of vibrationally excited H2 observed by the HST to calculate a model of the interstellar cloud toward HD 37903. We extend Mayer's analysis by including the v"=0 vibrational level observed by the FUSE satellite. The T01 temperature should not be interpreted as a rotational temperature, but rather as a temperature of thermal equilibrium between the ortho and para H2. The ortho to para H2 ratio is lower for collisionally populated levels than for the levels populated by fluorescence. The PDR model of the cloud located in front of HD 37903 points to a gas temperature Tkin=110-377 K, hydrogen density nH=1874-544 cm^-3 and the star-cloud distance of 0.45 pc

Les espèces végétales exotiques envahissantes dans les milieux naturels : analyse de leur gestion dans les parcs régionaux et nationaux du Québec de la région des Laurentides

Depuis plusieurs siècles, les espèces végétales exotiques envahissantes s’implantent dans les milieux naturels. Introduites à l’extérieur de leur aire de répartition historique par l’activité anthropique, leurs nombreux impacts sur l’environnement, l’économie et la société en font une menace importante. En effet, elles compétitionnent avec les espèces indigènes, entraînent de nombreux coûts, réduisent la valeur foncière d’un site, nuisent aux activités récréatives, causent des réactions cutanées sévères et plus encore. Les espèces exotiques envahissantes sont parmi les cinq principaux facteurs mondiaux de changements observés sur la nature depuis 50 ans et la deuxième plus importante menace pour la biodiversité. La gestion de ces espèces peut être effectuée par la prévention, l’éradication et le contrôle. Cependant, il peut être difficile d’appliquer ces mesures dans les aires naturelles, telles que les parcs nationaux du Québec et les parcs régionaux. Cet essai a pour objectif de guider les responsables des parcs régionaux et nationaux du Québec dans la gestion des espèces végétales exotiques envahissantes afin d’améliorer celle-ci à l’intérieur des espaces naturels. À cette fin, le cas des parcs régionaux et nationaux du Québec de la région des Laurentides a été analysé. Ainsi, la gestion des plantes exotiques envahissantes effectuée dans ces parcs est présentée, puis analysée par l’identification des points forts et des points faibles de chaque action, pour chacun des parcs. Les résultats de l’analyse montrent que de façon générale, la gestion des espèces végétales exotiques envahissantes reste à parfaire au Québec. Celle effectuée dans les parcs nationaux est plutôt adéquate, mais peut être améliorée, tandis que presque aucune gestion des espèces nuisibles n’est effectuée dans les parcs régionaux. En effet, puisque cela n’est généralement pas leur mission première, la plupart des responsables de ce type de parc ne possèdent pas d’inventaire floristique de leur territoire et n’effectuent pas d’action pour prévenir l’introduction de ces espèces. Les recommandations émises à la suite de cette analyse sont basées principalement sur les volets de sensibilisation, de prévention et de suivi. Les sujets abordés sont : les campagnes de sensibilisation et d’éducation, l’implication citoyenne, le resserrement de la règlementation, la création d’une loi spécifique aux espèces exotiques envahissantes, l’augmentation de la recherche scientifique et de l’acquisition de connaissances, le suivi des espèces et la formation des employés et des gestionnaires des parcs quant aux espèces végétales exotiques envahissantes

Classical and MgII-selected Damped Lyman-alpha Absorbers: impact on Omega_HI at z<1.7

The Damped Lyman-alpha systems (DLAs), seen in absorption in the spectrum of quasars, are believed to contain a large fraction of the neutral gas in the Universe. Paradoxically, these systems are more difficult to observe at z_abs<1.7, since they are rare and their HI feature then falls in UV spectra. Rao & Turnshek (2000) pioneered a method based on MgII-selected DLAs, that is absorbers discovered thanks to our knowledge of their MgII feature in optical spectra. We use new observations undertaken at the TNG as well as a careful literature & archival search to build samples of low redshift absorbers classified according to the technique used for their discovery. We successfully recover N(HI) and equivalent widths of FeII 2600, MgII 2796, MgII 2803 and MgII 2852 for a sample of 36 absorbers, 21 of which are MgII-selected. We find that the MgII-selected sample contains a marginally larger fraction of absorbers with log N(HI)>21.0 than seen otherwise at low redshift. If confirmed, this property will in turn affect estimates of Omega_HI which is dominated by the highest HI column densities. We find that log N(HI) does not correlate significantly with metal equivalent widths. Similarly, we find no evidence that gravitational lensing, the fraction of associated systems or redshift evolution affect the absorber samples in a different way. We conclude that the hint of discrepancies in N(HI) distributions most likely arises from small number statistics. Therefore, further observations are required to better clarify the impact of this discrepancy on estimates of Omega_HI at low redshift.Comment: 13 pages, 8 figures. Accepted for publication in MNRA

Impact d'un programme de toucher affectif appliqué par un proche parent à la personne atteinte d'une démence sévère

Cette étude vise donc à rassembler ces éléments et pose la question suivante:"Est-ce qu'un programme de toucher affectif implanté auprès des personnes âgées atteintes de démence avancée et appliqué par un membre de leur famille est en mesure d'améliorer la communication non verbale ainsi que la qualité de la relation entre les patients et les parents?". Il s'agit d'une étude longitudinale courte de type expérimentation de cas (multicas) suivant le protocole à cas unique ABA, ayant pour but de préciser la relation causale entre les variables. L'échantillon était constitué de cinq patients atteints d'une démence avancée accompagnés d'un membre de leur famille. Deux instruments de mesure ont été utilisés: la grille d'observation hebdomadaire des réactions au toucher affectif et un questionnaire d'entrevue. Les résultats ont été transposés sur graphiques pour en faire l'analyse de cas, et un test non paramétrique de Friedman a été utilisé afin de vérifier pour l'ensemble des sujets s'il y avait des différences significatives entre les parties avant, pendant et après --ABA-- l'intervention de toucher affectif."--Résumé abrégé par UMI

Searching for Dust Reddening in SDSS Spectra with Damped Lyman α\alpha{} Systems

We searched for evidence of reddening of background SDSS QSO spectra due to dust in intervening DLA systems. We utilise the Data Releases 5 and 7 to arrive at sample sizes of 475 (DR5) and 676 (DR7) absorbers, based on two different published lists of SDSS DLAs. Both samples span roughly the redshift range of 2.2 < z_abs < 5.2, with a mean of z~3.0, and the majority of the DLAs (75%) below z=3.3. We construct geometric mean spectra in the absorber restframes ranging from 1240 to ~2800 A, and composite spectra of samples matching the 'DLA' QSOs in i band magnitude and emission redshift z_em, but without absorption lines. By comparing the slopes of these composite spectra with their matched counterparts, we find no sign of reddening in the ensemble of the absorbers from these samples. Owing to both the unprecedently large sizes of the DLA samples themselves and the non-DLA SDSS QSO sample, from which we can draw our matching spectra, we can place very tight limits for this non-detection ( =-0.0013+-0.0025 (DR5) and =-0.0017+-0.0022 (DR7). Interestingly, when applying our technique to the samples of York et. al. (2006), vandenBerk et al. (2008) (intervening and intrinsic MgII absorbers) and the smaller DLA-subsample and pool of comparison QSOs of Vladilo et al. (2008), we do recover their results, i.e. detect the same amount of reddening as these authors do. Furthermore, we have tested whether subsamples of our large sample in categories involving the absorbers (HI column densities, presence or absence of accompanying metal absorption, absorber redshift) or the background quasars (emission redshift, brightness) do reveal dust extinction, but found no trends. These results are at odds with both detections of dust reddening from previous studies, and also with expectations from observations of high-redshift galaxies. (abridged)Comment: 16 pages, 12 figures, accepted for publication in MNRA

Star formation and chemical evolution of damped Lyman α\alpha systems

In this paper, we investigate the star formation and chemical evolution of damped Lyman-$\alpha$ systems (DLAs) based on the disc galaxy formation model which is developed by Mo, Mao & White. We propose that the DLAs are the central galaxies of less massive dark haloes present at redshifts $z\sim 3$, and they should inhabit haloes of moderately low circular velocity. The empirical Schmidt law of star formation rates, and closed box model of chemical evolution that an approximation known as instantaneous recycling is assumed, are adopted. In our models, when the predicted distribution of metallicity for DLAs is calculated, two cases are considered. One is that, using the closed box model, empirical Schmidt law and star formation time, the distribution of metallicity can be directly calculated. The other is that, when the simple gravitational instability of a thin isothermal gas disc as first discussed by Toomre is considered, the star formation occurs only in the region where the surface density of gas satisfies the critical value, not everywhere of a gas disc. We assume that star formation in each DLA lasts for a period of 1 Gyr from redshifts $z=3$. There is only one output parameter in our models, i.e. the stellar yield, which relates to the time of star formation history and is obtained by normalizing the predicted distribution of metallicity to the mean value of 1/13 $Z_{\odot}$ as presented by Pettini et al. The predicted metallicity distribution is consistent with the current (rather limited) observational data. A random distribution of galactic discs is taken into account.Comment: 7 pages, 6 figures, will appear in MNRAS, 2001 (21 April), 322, 927-93

Small scale structure in diffuse molecular gas from repeated FUSE and visible spectra of HD 34078

We present preliminary results from an ongoing program devoted to a study of small scale structure in the spatial distribution of molecular gas. Our work is based on multi-epoch FUSE and visible observations of HD34078. A detailed comparison of H2, CH and CH+ absorption lines is performed. No short term variations are seen (except for highly excited H2) but long-term changes in N(CH) are clearly detected when comparing our data to spectra taken about 10 years ago.Comment: 4 pages, 2 figures, To appear in the Proceedings of the XVII IAP Colloquium "Gaseous Matter in Galaxies and Intergalactic Space