1603.07422
Extended stellar components of galaxies & the nature of dark matter
Power, Robotham
Deep observations of galaxies reveal faint extended stellar components (ESCs) of streams, shells, and halos. These are a natural prediction of hierarchical galaxy formation, as accreted satellite galaxies are tidally disrupted by their host. Investigate whether or not global properties of the ESC could be used to test of DM, reasoning that they should be sensitive to the abundance of low-mass satellites, and therefore the underlying DM model. Using cosmo simulations of galaxy formation in the favored CDM and WDM models (m_WDM=0.5,1,2 keV/c^2), which suppress the abundance of low-mass satellites, find that the kinematics and orbital structure of the ESC is consistent across models. However, find striking differences in its spatial structure, as anticipated -- a factor of ~10 drop in spherically averaged mass density between ~10% and ~75% of the viral radius in the more extreme WDM runs (m_WDM=0.5, 1keV/c^2) relative to the CDM run. These differences are consistent with the mass assembly histories of the different components, and are present across redshifts. However, even the least discrepant of the WDM models is incompatible with current observational limits on m_WDM. Importantly, the differences observed when varying the underlying DM are comparable to the galaxy-to-galaxy variation expected within a fixed DM model. This suggests that it will be challenging to place limits on DM using only the unresolved spatial structure of the ESC.
1603.07519
Angular distribution of cosmological parameters as a probe of inhomogeneities: a kinematic parameterisation
Carvalho, Basilakos
Use a kinematic parameterization of the luminosity distance to measure the angular distribution of the sky of time derivatives of the scale factor, in particular the Hubble parameter H_0, the deceleration parameter q_0 and the jerk parameter j_0. Apply the method introduced in Carvalho & Marques (2015) to complement probing the inhomogeneity of the LSS by means of the inhomogeneity in the cosmic expansion. This parameteristion is independent of the cosmo equation of state, which renders it adequate to test interpretations of the cosmic acceleration alternative to the cosmo constant. Also measure the anisotropy of the parameters by computing the PS of the corresponding parameters' maps up to ell=3. Finally for an analytical toy model of an inhomogeneous ensemble of homogeneous pixels, derive the back reaction term in j_0 use to the fluctuations of {H+0,q+0} and measure it to be of order 0.01 the corresponding average over the pixels in the absence of back reaction. The back reaction effect on q_0 remains below the detection threshold, in agreement with that computed using a LCDM parameterization of the luminosity distance. Although the back reaction effect on j_0 is about 10x that on q_0, it is also below the detection threshold. Hence back reaction remains unobservable both in q_0 and in j_0.
1603.07722
RCSLenS: The Red Cluster Sequence Lensing Survey
Hildebrandt, et al
Present RCSLenS, and application of the methods developed for CFHTLenS to the ~785 deg^2, multi-band imaging data of RCS2. This project represents the largest public, sub-acrsecond seeing, multi-band survey to date that is suited for WL measurements. With a careful assessment of systematic errors in shape measurements and photometric redshifts, extend the use of this data set to allow cross-correlation analysis between WL observables and other data sets. Describe the imaging data, the data reduction, masking ,multicolor photometry, photo-z, shape measurements, tests for systematic errors, and a blinding scheme to allow for more objective measurements. In total, analyze 761 pointings with r-band coverage, which constitutes the lensing sample. Residual large-scale B-mode systematics prevent the use of this shear catalog for cosmic shear science. The effective number density of lensing sources over an unmasked area of 751.7 deg^2 and down to a magnitude limit of r~24.5 is 8.1 galaxies per arcmin^2 (weighted: 5.5 arcmin^-2) distributed over 14 patches on the sky. Photometric redshifts based on 4-band griz data are available for 513 pointings covering an unmasked area of 383.5 deg^2. Present WL mass reconstructions of some example clusters as well as the full survey representing the largest areas that have been mapped in this way. All the data products are publicly available through CADC at www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/en/community/rcslens/query.html in a format very similar to the CFHTLenS data release.
1603.07723
CFHTLenS and RCSLenS Cross-correlation with Planck Lensing detecting in Fourier and configuration space
Harnois-Déraps, et al
Measure the cross-correlation signature between the Planck CMB lensing map and the WL observations from both the RCSLenS and CFHTLenS. In addition to a Fourier analysis, include the first configuration-space detection, based on the estimators <k_CMB k_gal> and <k_CMB gamma_t>. Combining 747.2 deg^2 from both surveys, find a detection significance that exceeds 4.2 sigma in both Fourier- and configuration-space analyses. Scaling the predictions by a free parameter A, obtain A^Planck_CFHT=0.68±0.31 and A^Planck_RCS=1.31±0.33. In preparation for the next generation of measurements similar to these, quantify the impact of different analysis choices on these results. First, since none of these estimators probes the exact same dynamical range, improve the detection by combining them. Second, carry out a detailed investigation on the effect of apodization, zero-padding and mask multiplication, validated on a suite of high-resolution simulations, and find that the latter produces the largest systematic bias in the cosmo interpretation. Finally, show that residual contamination from intrinsic alignment and the effect of photo-z error are both largely degenerate with the characteristic signal from massive neutrinos, however the signature of baryon feedback might be easier to distinguish. The RCSLenS lensing data are now publicly available.
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