Day 490

Saturday.

1308.3249
Galactic abundance gradients from Cepheids: alpha and heavy elements in the outer disk
Lemasle, et al

Galactic abundance gradients set strong constraints to chemo-dynamical evolutionary models of the MW.  Given the PL relations that provide accurate distances and the large number of spectral lines, Cepheids are excellent tracers of the present-day abundance gradients.  Want to measure the Galactic abundance gradient of several chemical elements.  While the slope of the Cepheid Fe gradient did not vary much from the very first studies, the gradients of the other elements are not that well constrained.  In this paper, focus on the inner and outer regions of the Galactic thin disk.  Use HR spectra to measure abundances of several light (Na, Al), alpha (Mg, Si, S, Ca) and heavy (Y, Zr, La, Ce, Nd, Eu) in a sample of 65 MW Cepheids.  Combining these results with accurate distances from period-Wesenheit relations in the NIR enables us to determine the abundance gradients in the MW.  Results are in good agreement with previous studies on either Cepheids or other tracers.  In particular, confirm an upward shift of approximately 0.2 dex for the Mg abundances, as has recently been reported. Also confirm the existence of a gradient for all the heavy elements studied in the context of a LTE analysis.  However, for Y, Nd, and especially La, find lower abundances for Cepheids in the outer disk than reported in previous studies, leading to steeper gradients.  This effect can be explained by the differences in the line lists used by different groups.  Data do not support a flattening of the gradients in the outer disk, in agreement with recent Cepheid studies and chemo-dynamical simulations.  This is in contrast to the open cluster observations but remains compatible with a picture where the transition zone between the inner disk and the outer disk would move outward with time.

1308.3255
A new life for sterile neutrinos: resolving inconsistencies using hot dark matter
Hamann, Hasenkamp

If LCDM is extended by a hot dark matter component, which could be interpreted as a sterile neutrino, the data sets can be combined consistently.  A combination of Planck data, WMAP-9 polarization data, measurements of the BAO scale, the HST measurement of H_0, Planck galaxy cluster counts and galaxy shear data from the CFHTLens survey yields Delta N_eff=0.61pm0.30 and m_s^eff=0.41 pm 0.13 eV at 1 sigma.  The former is driven mainly by the large H_0 of the HST measurement, while the latter is driven by cluster data.  CFHTLens galaxy shear data prefer Delta N_eff>0 and a non-zero mass.  Taken together, find hints for the presence of a hot DM component at 3 sigma.  A sterile neutrino motivated by the reactor and gallium anomalies appears rejected at even higher significance and an accelerator anomaly sterile neutrino is found in tension at 2 sigma.

1308.3346
Probing the Sun's inner core using solar neutrinos: a new diagnostic method
Lopes

The electronic density in the Sun's inner core is inferred from the 8B, 7Be and pep neutrino flux measurements of the Super-Kamiokande, SNO and Borexino experiments.  Developed a new method in which the KamLAND detector determinations of the neutrino fundamental oscillation parameters [?]: the mass difference and the vacuum oscillation angle.  Results suggest that the solar electronic density in the Sun's inner core (for a radius smaller than 10% of the solar radius) is well above the current prediction of the standard solar model, and by as much as 25%.  A potential confirmation of these preliminary findings can be achieved when neutrino detectors are able to reduce the error of the electron-neutrino survival probability by a factor of 15.