Day 832

Thursday, Karneval started.

1502.03099
Cosmology with anisotropic galaxy clustering from the combination of power spectrum and bispectrum
Song, Taruya, Oka

The apparent anisotropies of the galaxy clustering in observable z-space provide a unique opportunity to simultaneously probe cosmic expansion and gravity on cosmological scales via the Alcock-Paczynski effect and z-space distortions.  While the improved theoretical models have been proposed and developed to describe the apparent anisotropic clustering at weakly NL scales, the applicability of these models is still limited in the presence of the non-perturbative smearing effect caused by the randomness of the relative velocities.  Although the cosmological constraint from the anisotropic clustering will be certainly improved with a more elaborate theoretical model, consider an alternative way by using the statistical power of both the power spectrum and bispectrum at large scales.  Based on the Fisher matrix analysis, estimate the benefit of combining the power spectra and bispectra, finding that the constraints on the cosmic expansion and growth of structure will be improved by a a factor of two.  This compensates for the loss of constraining power using the PS alone due to the randomness of the relative velocities.

1502.03107
Detecting the integrated Sachs-Wolfe effect with high-redshift 21-cm surveys
Raccanelli, Kovetz, Dai, Kamionkowski

Investigate the possibility to detect ISW by cross-correlating 21-cm surveys at high z with galaxies, in a way similar to the CMB-galaxy X-correlation.  The high-z 21-cm signal is dominated by CMB photons that travel freely without interacting with the intervening matter, and hence its late-time ISW signature should correlate extremely well with that of the CMB at its peak frequencies.  Using the 21-cm temperature brightness instead of the CMB would thus be a further check on the detection of the ISW effect, measured by different instruments at different frequencies and suffering from different systematics.  Also study the ISW effect on the photons that are scattered by HI clouds.  Show that a detection of the unscathed photons is achievable with planned radio arrays, while one using scattered photons will require advanced radio interferometer, either an extended version of the planned Square Kilometer Array or futuristic experiments such as a lunar radio array.

1502.03141
Distortion of the luminosity function of high-redshift galaxies by gravitation lensing
Fialkov, Loeb

The observed properties of high-z galaxies depend on the underlying FG distribution of LSS, which distorts their intrinsic properties via GL.  Focus on the regime where the dominant contribution originates from a single lens and examine the statistics of GL by a population of virtualized and non-vilrialized structures using sub-mm galaxies at z~2.6 and Lyman-break galaxies at z~6-15 as the BG sources.  Quantify the effect of lensing on the LF of the high-z sources, focusing on the intermediate and small magnifications (mu<3) which affect the majority of the background galaxies.  Show that depending on the intrinsic properties of the FG galaxies, GL can significantly affect the observed LF even when no obvious SLs are present.  Find that in the case of the Lyman-break galaxies, it is important to account for the surface brightness profiles of both the FG and BG galaxies when computing the lensing statistics, which introduces a selection criterion for the BG galaxies that can actually be observed.  Not taking this criterion into account leads to an overestimation of the number densities of very bright galaxies by nearly 2 orders of magnitude.

1502.03405
Cross-correlation of CFHTLenS galaxy number density and Planck CMB lensing
Omori, Holder

Measure the X-PS between galaxy density from CFHTLenS catalogues and gravitational lensing convergence from Planck DR1 (2013) and DR2 (2015).  Investigate 3 main galaxy samples: 18.0<i_AB<22.0, 18.0<i_AB<23.0, 18.0<i_AB<24.0, in 0.2<z<1.3 in each of the 4 CFHTLenS wide fields.  By comparing the measured X-spectrum with model predictions, linear galaxy-DM basis of b=0.82, 0.83, 0.82 are inferred at significances of 3.5, 4.5, 5.6 sigma using the Planck 2015 release.  These measurements are marginally consistent with biases derived from g-g auto-correlations: b=1.15, 1.08, and 0.96 respectively.  Using the 2013 Planck release, obtain biases of b=1.33, 1.19, 1.16, showing significant differences between the releases.

1502.03429
Internal alignments of red versus blue disks in dark matter halos
Debattista, van den Bosch, Roskar, Quinn, Moore, Cole

Large surveys have shown that red galaxies are preferentially aligned with their haloes while blue galaxies have a more isotropic distribution.  Since haloes generally align with their filaments, this introduces a bias in the measurement of the cosmic shear from WL.  It is therefore vitally important to understand why this difference arises.  Explore the stability of different disc orientations within triaxial haloes.  Show that, in the absence of gas, the disc orientation is most stable when its spin is along the minor axis of the halo.  Instead when gas cools onto a disc, it is able to form in almost arbitrary orientation, including off the main planes of the halo (but avoiding an orientation perpendicular to the halo's intermediate axis).  Substructure helps gases galaxies reach alignment with the halo faster, but have less effect on galaxies when gas is cooling onto the disc.  Results provide a novel and natural interpretation for why red, gas poor galaxies are preferentially aligned with their halo, while blue, SF, galaxies have nearly random orientations, without requiring a connection between galaxies' current SFR and their merger history.