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

Stellar mass functions of galaxies, disks and spheroids at z~0.1

We present the stellar mass functions (SMF) and mass densities of galaxies, and their spheroid and disk components in the local (z~0.1) universe over the range 8.9 <= log(M/M_solar) <= 12 from spheroid+disk decompositions and corresponding stellar masses of a sample of over 600,000 galaxies in the SDSS-DR7 spectroscopic sample. The galaxy SMF is well represented by a single Schechter function (M* = 11.116+/-0.011, alpha = -1.145+/-0.008), though with a hint of a steeper faint end slope. The corresponding stellar mass densities are (2.670+/-0.110), (1.687+/-0.063) and (0.910+/-0.029)x10^8 M_solar Mpc^-3 for galaxies, spheroids and disks respectively. We identify a crossover stellar mass of log(M/M_solar) = 10.3+/-0.030 at which the spheroid and disk SMFs are equal. Relative contributions of four distinct spheroid/disk dominated sub-populations to the overall galaxy SMF are also presented. The mean disk-to-spheroid stellar mass ratio shows a five fold disk dominance at the low mass end, decreasing monotonically with a corresponding increase in the spheroidal fraction till the two are equal at a galaxy stellar mass, log(M/M_solar)=10.479+/-0.013, the dominance of spheroids then grows with increasing stellar mass. The relative numbers of composite disk and spheroid dominated galaxies show peaks in their distributions, perhaps indicative of a preferred galaxy mass. Our characterization of the low redshift galaxy population provides stringent constraints for numerical simulations to reproduce.Comment: 30 pages, 18 figures, 5 tables (2 online), Accepted for publication in MNRA

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

Pluralism as a Bias Mitigation Strategy

An agnostic pluralist approaches inquiry with the assumption that it is possible for more than one account of the phenomenon in question to be correct. A monist approaches inquiry with the assumption that only one account of the phenomenon in question is correct. The purpose of my paper is to support the claim that agnostic pluralists are less susceptible to a sort of bias that I call dialectical bias than monists

On deductivism : a critical survey of deductivism in informal logic

The aim of this thesis is to understand and critically evaluate deductivism as a theory of inferential sufficiency in informal logic. I distinguish three different types of deductivism: strong normative deductivism, weak normative deductivism, and reconstructive deductivism. I also discuss some potential justificatory strategies that might be invoked in an attempt to justify strong normative deductivism and reconstructive deductivism. I apply this categorization scheme to develop an interpretation of Leo Groarke\u27s version of reconstructive deductivism. I then evaluate some of the criticisms of deductivism raised in the informal logic literature. I focus in particular on the criticisms of Ralph Johnson and Trudy Govier. I follow up this evaluation by raising some problems for the justificatory strategies used to support deductivism. I also show how these problems apply to Groarke\u27s reconstructive deductivism

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