Results from the search for neutrinoless double beta decay with NEMO-3 and The SuperNEMO project

International audienceThe NEMO-3 experiment located in the Modane Underground Laboratory (LSM) is searching for neutrinoless double beta decay. The experiment has been taking data since 2003 with a range of isotopes. The main isotopes are ~ 7 kg of 100Mo and ~ 1 kg of 82Se. Since no evidence for neutrinoless double beta decay has been found, a 90% Confidence Level lower limit on the half-life of this process is derived. From this we determine an upper limit on the effective Majorana neutrino mass. New results using 150Nd, an isotope of special interest due to its potential use in future experiments, will also be presented. The data are also interpreted in terms of alternative models, such as weak right-handed currents or Majoron emission. NEMO-3 has also performed precision measurements of the standard model double beta decay process for several isotopes. Measurements of this process are important for reducing the uncertainties on nuclear matrix elements. A precise measurement of the half-life for the double beta decay of 130Te and a comparison with the conflicting results from geochemical experiments has also been performed. The most recent experimental results of NEMO-3 will be presented

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

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

First results of the NEMO3 experiment

The objective of the NEMO Collaboration is to search for neutrinoless double beta decay and thus to investigate physics beyond the Standard Model. The expected sensitivity for the effective neutrino mass is on the order of 0.1 eV. The NEMO-3 detector has been operating in the Fréjus Underground Laboratory and has been collecting data since February of 2003. The half-life of two-neutrino double beta decay has been measured for 100Mo and 82Se. Constraints on the background for neutrinoless double beta decay have been set. PACS: 23.40.-s Beta decay; double beta decay; electron and muon capture – 14.60.Pq Neutrino mass and mixin

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

The SBF Survey of Galaxy Distances. I. Sample Selection, Photometric Calibration, and the Hubble Constant

We describe a program of surface brightness fluctuation (SBF) measurements for determining galaxy distances. This paper presents the photometric calibration of our sample and of SBF in general. Basing our zero point on observations of Cepheid variable stars, we find that the absolute SBF magnitude in the Kron-Cousins I band correlates well with the mean (V-I)o color of a galaxy according to M_Ibar = (-1.74 +/- 0.07) + (4.5 +/- 0.25) [ (V-I)o - 1.15 ] for 1.0 < (V-I) < 1.3. This agrees well with theoretical estimates from stellar population models. Comparisons between SBF distances and a variety of other estimators, including Cepheid variable stars, the Planetary Nebula Luminosity Function (PNLF), Tully-Fisher (TF), Dn-sigma, SNII, and SNIa, demonstrate that the calibration of SBF is universally valid and that SBF error estimates are accurate. The zero point given by Cepheids, PNLF, TF (both calibrated using Cepheids), and SNII is in units of Mpc; the zero point given by TF (referenced to a distant frame), Dn-sigma and SNIa is in terms of a Hubble expansion velocity expressed in km/s. Tying together these two zero points yields a Hubble constant of H_0 = 81 +/- 6 km/s/Mpc. As part of this analysis, we present SBF distances to 12 nearby groups of galaxies where Cepheids, SNII, and SNIa have been observed.Comment: 29 pages plus 8 figures; LaTeX (AASTeX) uses aaspp4.sty (included); To appear in The Astrophysical Journal, 1997 February 1 issue; Compressed PostScript available from ftp://mars.tuc.noao.edu/sbf