Day 828

Thursday.  Friday.

1502.01349
On the diffuse Lyman-alpha halo around Lyman-alpha emitting galaxies
Lake et al

Lya photons scattered by neutral H atoms in the circumgalactic media or produced in the halos of SF galaxies are expected to lead to extended Lya emission around galaxies.  Such low surface brightness Lya halos (LAHs) have been detected by stacking Lya images of high-z SF galaxies.  Study the origin of LAHs by performing radiative transfer modeling of 9 z=3.1 LAEs in a high-res hydro galaxy formation sim.  Develop a method of computing the mean Lya surface brightness profile of each LAE by effectively integrating over many different observing directions.  Without adjusting any parameters, the model yields an average Lya surface brightness profile in remarkable agreement with observations.  Find that observed LAHs can not be accounted for solely by photons originating from the central LAE and scattered to large radii by hydrogen atoms in the circumgalactic gas.  Instead, Lya emission from regions in the outer halo is primarily responsible for producing the extended LAHs seen in observations, which potentially includes both SF and cooling radiation.  The contribution from SF in the outer halo regions can be strongly constrained to be negligible by the observed absence of an extended UV halo.  The results therefore suggest that cooling radiation from the outer halo regions of LAEs plays a major role in forming their extended LAHs.  Discuss the implications and caveats of such a picture.

1502.01353
Tailoring strong lensing cosmographic observations
Linder

SL time delay cosmography has excellent complementarity with other DE probes, and will soon have abundant systems detected.  Investigate two issues in the imaging and spectroscopic followup required to obtain the time delay distance.  The first is optimization of spectroscopic resources.  Develop a code to optimize the cosmo leverage under the constrain of constant spectroscopic time, and find that sculpting the lens system redshift distribution can deliver a 40% improvement in DE FoM.  The second is the role of systematics, correlated between different quantities of a given system or model errors common to all systems.  Show how the levels of different systematics affect the cosmological parameter estimation, and derive guidance for the fraction of double image vs quad image systems to follow as a function of differing systematics between them.

1502.01589
Planck 2015 results.  XIII. Cosmological parameters
Planck Collaboration

Present results based on full-mission Planck observations of temperature and polarization anisotropies of the CMB.  These data are consistent with the six-parameter inflationary LCDM cosmology.  From the Planck temperature and lensing data, for this cosmology find a Hubble constant, H0=67pm0.9 km/s/Mpc, a matter density parameter Omega_m=0.38pm0.012, and a scalar spectral index with n_s=0.968pm0.006 (quote 68% errors on measured parameters and 95% limits on other parameters).  Combined with Planck temperature and lensing data, Planck LFI polarization measurements lead to a deionization optical depth of tau=0.066pm0.016.  Combining Planck with other astrophysical data, find N_eff = 3.15pm0.23 for the effective number of relativistic degrees of freedom and the sum of neutrino masses is constrained to <0.23 eV.  Spatial curvature is found to be |Omega_K|<0.005.  For LCDM find a limit on the tensor-to-scalar ratio of r<0.11 consistent wit the B-mode constraints from an analysis of BICEP2, Keck Array, and Planck (BKP) data.  Adding the BKP data leads to a tighter constraint of r<0.09.  Find no evidence for isocurvature perturbations or cosmic defects.  The equation of state of DE is constrained to w=-1.006pm0.045.  Standard BB nucleosynthesis predictions for the Planck LCDM cosmology are in excellent agreement with observations.  Investigate annihilating DM and deviations from standard recombination, finding no evidence for new physics.  The Planck results for base LCDM are in agreement with BAO data and with the JLA SNe sample.  However, the amplitude of the fluctuations is found to be higher than inferred from rich cluster counts and weak gravitational lensing.  Apart from these tensions, the base LCDM cosmology provides an excellent description of the Planck CMB observations and many other astrophysical data sets.

1502.01591
Planck 2015 results.  XV.  Gravitational lensing
Planck Collaboration, et al

Present the most significant measurement of the CMB lensing potential to date (40 sigma), using temperature and polarization data from the Planck 2015 full-mission release.  Using a polarization-only estimator, detect lensing at a significance of 5 sigma.  Cross-check the accuracy of the measurement using the wide frequency coverage and complementarity of the temperature and polarization measurements.  Public products based on this measurement include an estimate of the lensing potential over approximately 70% of the sky, and estimate of the lensing potential power spectrum in band powers for the multipole range 40<L<400 and an associated likelihood for cosmological parameter constraints.  Find good agreement between measurement of the lensing potential PS and that found in the best-fitting LCDM model based on the Planck temperature and polarization power spectra.  Using the lensing likelihood alone, obtain a percent-level measurement of the parameter combination Sigma_8 Omega_m^0.25 = 0.591pm0.021.  Combine determination of the lensing potential with the E-mode polarization also measured by Planck to generate an estimate of the lensing B-mode.  Show that this lensing B-mode estimate is correlated with the B-modes observed directly by Planck at the expected level and with a statistical significance of 10 sigma, confirming Planck's sensitivity to this known sky signal.  Also correlate lensing potential estimate with the LS temperature anisotropies, detecting a cross-correlation at the 3 sigma level, as expected due to DE in the concordance LCDM model.