MG14 - Talk detail

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Whitbourn & Shanks (2014, MNRAS 437, 2146) have analysed galaxy redshift survey data out to ~300h-1Mpc scales and find evidence for a "Local Hole" ie a local under density that extends to 100-200h-1 Mpc. The "Local Hole" is particularly prominent in the Southern Hemisphere where it is underdense by ~50%. This result confirms previous work by Busswell et al (2004) and Frith et al (2006) mostly based on galaxy number magnitude counts but the new results are more robust, built on complete galaxy redshift surveys. Whitbourn & Shanks (2015) have further confirmed the existence of the Local Hole, now using clustering independent estimates of the galaxy luminosity function rather than simply using an assumed luminosity function. We demonstrate that the recent independent results of Keenan et al (2013) using other galaxy redshift surveys and Bohringer et al (2015) using a complete X-ray cluster survey are completely consistent with our results. We discuss possible links to the CMB Cold Spot which exists in a subset of our Southern "Local Hole" area. We further discuss possible implications for the interpretation of the Type Ia supernova and BAO Hubble diagrams.

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