Dark Energy and Modified gravity
Is the CMB Cold Spot Evidence of Modified Gravity?
Ruari Mackenzie
Shanks, T. (Durham)
University of Durham
The CMB Cold Spot remains one of the few anomalies of the microwave sky, suggested to be evidence of a departure from Gaussianity and standard cosmology at 2-3 sigma significance. Many attempts have been made to establish explanations for the Cold Spot including the ISW imprint of a large void. However the scale of void required to produce such an imprint disfavored this hypothesis as it was itself more unlikely to arise in LCDM than the Cold Spot. The reported detection of an unusually large void aligned with the Cold Spot in 2015 changed this argument; it was claimed that the peculiarity of such a void and its coincidence with the CMB Cold Spot pointed to a causal connection which couldn't be explained by LCDM. Some modified gravities have enhanced ISW effects. We report the results of a z~0-0.4 redshift survey carried out on AAOmega based on imaging from the VST ATLAS survey over the core of the CMB Cold Spot. We sparsely surveyed the inner 5 deg radius of the Cold Spot to a limit of i =19.2, sampling ~7000 galaxies. The survey aimed to measure the void parameters with spectroscopic precision in order to assess the significance of the void and test the claim that this points to an effect beyond LCDM.
13:30 - 15:00
BS - Lecture Theatre A25 (121)