1704.03461
Baryons still trace dark matter: probing CMB lensing maps for hidden isocurvature
Smith, et al
Compensated isocurvature perturbations (CIPs) are primordial fluctuations that balance baryon and DM isocurvature to leave the total matter density unperturbed. The effects of CIPs on the CMB anisotropies are similar to those produced by WL of the CMB: smoothing of the power spectrum, and generation of non-Gaussian features. Previous work considered the CIP effects on the CMB PS but neglected to include the CIP effects on estimates of the lensing potential power spectrum (though its contribution to the non-Gaussian, connected, part of the CMB trispectrum). Here, the CIP contribution to the standard estimator for the lensing potential power-spectrum is derived, and along with the CIP contributions to the CMB PS, Planck data is used to place limits on the RMS CIP fluctuations on CMB scales, Delta^2_rms(R_CMB). The resulting constraint of Delta^2_rms(R_CMB)<4.3e-3 using this new technique improves on past work by a factor of ~3. Find that for Planck data, the constraints almost reach the ensitivity of the optimal CIP estimator. The method presented here is currently the most sensitive probe of the amplitude of scale-invariant CIP PS placing an upper limit of A_CIP<0.017 at 95% CL. Future meausrements of the LS CMB lensing potential power spectrum could probe CIP amplitudes as low as Delta^2_rms(R_CMB)=8e=5 (A_CIP=3.2e-4).
1704.03814
Evidence against a supervoid causing the CMB cold spot
Mackenzie, et al
Report the results of the 2dF-VST ATLAS Cold Spot galaxy redshift survey (2CSz) based on imaging from VST ATLAS and spectroscopy from 2dF AAOmega over the core of the CMB Cold Spot. Sparsely survey the inner 5deg radius of the Cold Spot to a limit of i_AB<=19.2, sampling ~7000 galaxies at z<0.4. Found voids at z=0.14,0.26 and 0.30 but they are interspersed with small over-densities and the scale of these voids is insufficient to explain the Cold Spot through the LCDM ISW effect. Combining with previous data out to z~1, conclude that the CMB Cold Spot could not have been imprinted by a void confined to the inner core of the Cold Spot. Additionally, find that the 'control' field GAMA G23 shows a similarity in its galaxy redshift distribution to the Cold Spot. Since the GAMA G23 LoS shows no evidence of a CMB temperature decrement, conclude that the Cold Spot may ave a primordial origin rather than being due to LoS effects.
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