Bulge plus disc and S\'ersic decomposition catalogues for 16,908 galaxies in the SDSS Stripe 82 co-adds: A detailed study of the ugrizugriz structural measurements

Quantitative characterization of galaxy morphology is vital in enabling comparison of observations to predictions from galaxy formation theory. However, without significant overlap between the observational footprints of deep and shallow galaxy surveys, the extent to which structural measurements for large galaxy samples are robust to image quality (e.g., depth, spatial resolution) cannot be established. Deep images from the Sloan Digital Sky Survey (SDSS) Stripe 82 co-adds provide a unique solution to this problem - offering $1.6-1.8$ magnitudes improvement in depth with respect to SDSS Legacy images. Having similar spatial resolution to Legacy, the co-adds make it possible to examine the sensitivity of parametric morphologies to depth alone. Using the Gim2D surface-brightness decomposition software, we provide public morphology catalogs for 16,908 galaxies in the Stripe 82 $ugriz$ co-adds. Our methods and selection are completely consistent with the Simard et al. (2011) and Mendel et al. (2014) photometric decompositions. We rigorously compare measurements in the deep and shallow images. We find no systematics in total magnitudes and sizes except for faint galaxies in the $u$-band and the brightest galaxies in each band. However, characterization of bulge-to-total fractions is significantly improved in the deep images. Furthermore, statistics used to determine whether single-S\'ersic or two-component (e.g., bulge+disc) models are required become more bimodal in the deep images. Lastly, we show that asymmetries are enhanced in the deep images and that the enhancement is positively correlated with the asymmetries measured in Legacy images.Comment: 27 pages, 14 figures. MNRAS accepted. Our catalogs are available in TXT and SQL formats at http://orca.phys.uvic.ca/~cbottrel/share/Stripe82/Catalogs

Alien Registration- Simard, Henri J. (Auburn, Androscoggin County)

https://digitalmaine.com/alien_docs/30400/thumbnail.jp

The signature of dissipation in the mass-size relation: are bulges simply spheroids wrapped in a disc?

The relation between the stellar mass and size of a galaxy's structural subcomponents, such as discs and spheroids, is a powerful way to understand the processes involved in their formation. Using very large catalogues of photometric bulge+disc structural decompositions and stellar masses from the Sloan Digital Sky Survey Data Release Seven, we carefully define two large subsamples of spheroids in a quantitative manner such that both samples share similar characteristics with one important exception: the 'bulges' are embedded in a disc and the 'pure spheroids' are galaxies with a single structural component. Our bulge and pure spheroid subsample sizes are 76,012 and 171,243 respectively. Above a stellar mass of ~$10^{10}$ M$_{\odot}$, the mass-size relations of both subsamples are parallel to one another and are close to lines of constant surface mass density. However, the relations are offset by a factor of 1.4, which may be explained by the dominance of dissipation in their formation processes. Whereas the size-mass relation of bulges in discs is consistent with gas-rich mergers, pure spheroids appear to have been formed via a combination of 'dry' and 'wet' mergers.Comment: Accepted for publication in MNRAS, 6 pages, 3 figure

Clues to the Origin of the Mass-Metallicity Relation: Dependence on Star Formation Rate and Galaxy Size

We use a sample of 43,690 galaxies selected from the Sloan Digital Sky Survey Data Release 4 to study the systematic effects of specific star formation rate (SSFR) and galaxy size (as measured by the half light radius, r_h) on the mass-metallicity relation. We find that galaxies with high SSFR or large r_h for their stellar mass have systematically lower gas phase-metallicities (by up to 0.2 dex) than galaxies with low SSFR or small r_h. We discuss possible origins for these dependencies, including galactic winds/outflows, abundance gradients, environment and star formation rate efficiencies.Comment: Accepted by ApJ Letter

Les enjeux territoriaux associés à la réforme municipale au Québec. Le cas de Saguenay

Depuis une décennie, les réorganisations politico-administratives locales et régionales sont fréquentes en Occident. Le Québec n’échappe pas à la tendance avec la réforme municipale en cours. Les regroupements de municipalités de 2001 ont ainsi affecté les six régions métropolitaines de la province et plusieurs agglomérations de plus petite taille. Cet article a pour objectif de faire ressortir les enjeux territoriaux de l’intégration socio-économique et fonctionnelle de ces nouveaux espaces politiques. À cette fin, nous regarderons la situation de Saguenay au Québec. Cette ville moyenne en région périphérique se distingue à divers égards. Elle est une agglomération possédant plusieurs centres d’affaires ayant des caractéristiques propres. Ceux-ci correspondent aux secteurs centraux des anciennes villes de Chicoutimi, Jonquière et La Baie. Par ailleurs, Saguenay est le coeur d’un espace rural agro-forestier qui possède maintenant une autonomie administrative compte tenu de la création d’une nouvelle municipalité régionale de comté (MRC). Comment seront gérées les dynamiques intra-urbaines et régionales dans le contexte de cette réorganisation administrative?Local government reforms are popular in Western societies these days. The province of Québec (Canada) is not different in this regard. The 2001 municipal reform has resulted in major changes, namely the amalgamation of numerous towns and cities in and around six key metropolitan areas (Montréal, Québec City, Gatineau, Saguenay, Sherbrooke and Trois-Rivières). This article attempts to explore the land use planning and local democracy issues that face newly elected bodies. The case of Saguenay is used as an example of an average city based in a resource-economy region. Saguenay was created through the merger of Chicoutimi, Jonquière, La Baie and four other municipalities. The merger has been difficult to implement in a multi-centred urban region with strong local identities

The ribosomal protein RACK1 is required for microRNA function in both C. elegans and humans

Despite the importance of microRNAs (miRNAs) in gene regulation, it is unclear how the miRNA-Argonaute complex-or miRNA-induced silencing complex (miRISC)-can regulate the translation of their targets in such diverse ways. We demonstrate here a direct interaction between the miRISC and the ribosome by showing that a constituent of the eukaryotic 40S subunit, receptor for activated C-kinase (RACK1), is important for miRNA-mediated gene regulation in animals. In vivo studies demonstrate that RACK1 interacts with components of the miRISC in nematodes and mammals. In both systems, the alteration of RACK1 expression alters miRNA function and impairs the association of the miRNA complex with the translating ribosomes. Our data indicate that RACK1 can contribute to the recruitment of miRISC to the site of translation, and support a post-initiation mode of miRNA-mediated gene repression. © 2011 European Molecular Biology Organization