Day 85

Monday.  Hope to get back into the swing of things (in research).

1109.3458

Modelling larg-scale halo bias using the bispectrum

Pollack, Smith, Porciani

Study halo bias in LCDM, quadratic order in matter density, characterized by b1 and b2.  Estimate parameters using N-body simulations.  Smooth both matter and halo: bias parameters vary by smoothing scale.  Real space has no parameters independent of smoothing.  In Fourier space: measure halo power spectra, construct estimates for effective large-scale bias.  Measure configuration dependence of the halo bispectra B_hhh and reduced bispectra Q_hhh for very large-scale k-space triangles (is this small k?).  Constrain b_1 and b_2 from these.  For B_hhh the best-fit parameters are in reasonable agreement with lowest-order perturbation theory as the triangle scale is varied, but poor as smaller scales are included; similar for Q_hhh.  For k1>0.03h/Mpc, Results for B_hhh and Q_hhh are incompatible.  "Discreteness correction" dependence seen in best-fit parameters.  Consider halo-mass cross-bispectra; results support earlier findings.  Develop a test to explore significance of higher-order terms in the models.  Low order expansions are not able to correctly model the data, even for k1~0.04h/Mpc.  If robust references drawn are to be drawn from galaxy surveys, then accurate models for the full nonlinear matter bispectrum and trispectrum will be essential (?).

1109.3460
Testing scaling relations for solar-like oscillations from the main sequence to red giants using Kepler data
Huber et al.


* what is a "solar-like oscillation"?  --Astroseismic activity, it seems.


~1700 main-to-red stars from Kepler.  Use evolutionary models to test astroseismic scaling relations for the frequency of maximum power (nu_max), the large frequency separation (Delta_nu) and oscillation amplitudes.  Difference in the Delta-nu-nu_max relation for unevolved and evolved stars can be explained by different distributions in effective temperature and stellar mass, in agreement with scaling relations (but not for red giant stars).  Revised scaling relation with separate luminosity-mass dependence can be used to calculate amplitudes from main-sequence to red-giants to a precision of ~25%.  Investigate correlations between amplitudes and stellar activity; find evidence that amplitude suppression is most pronounced for subgiant stars.  Test location of cool edge of the instability strip in the HR diagram using solar-like oscillations and find the detections in the hottest stars [are] compatible with domain of stochastically excited and opacity driven pulsation.


1109.3461
Search for z~7 Ly-alpha emitters with Suprime-Cam at the Subaru Telescope
Hibon, Kashikawa, Willott, Iye, Shibuya


Search for z=7 LAE using custom-made narrow band filter at 9755A on Suprime-cam.  Two fields, 7 candidates, 4 robust.  Derive possible z~7 Ly-alpha luminosity functions for the full samples and for a subsample of 4 objects in each field.  No strong evolution between the z=6.5 and 7 LyA luminosity functions.  Spectroscopic confirmation for the candidate samples required for a definitive measure of luminosity function at z~7.