All-sky galaxy surveys: recent results and future prospects

The new astronomy seminar room (RW James level 5, next to the astronomy library)
Tue, 28/04/2015 - 13:00 - 14:00
Maciej Bilicki (UCT)

Wide-angle galaxy redshift surveys such as the Sloan Digital Sky Survey have revolutionized our knowledge of the Universe. A trade-off between depth and sky coverage of such spectroscopic surveys limits however a systematic three-dimensional account of the entire sky beyond the Local Volume, while various aspects of cosmology require comprehensive mapping of the cosmic web to considerable depths. In order to probe the whole extragalactic sky beyond 100 megaparsecs, one must draw on multiwavelength datasets and state-of-the-art photometric redshift techniques. I will summarise the current status of our dedicated programme to employ the largest photometric all-sky surveys – 2MASS, WISE and SuperCOSMOS – to obtain accurate redshift estimates of millions of galaxies. The first outcome of these efforts – the 2MASS Photometric Redshift catalogue (2MPZ) – was publicly released in 2013 and includes almost 1 million galaxies with a median depth over 300 Mpc. I will detail how this catalogue was constructed and how it is being used for various cosmological tests. I will also present how combining the WISE mid-infrared survey with SuperCOSMOS optical data allows us to push to depths over 1 gigaparsec on unprecedented angular scales. These photometric redshift samples, with about 20 million sources in total, provide access to volumes large enough to study observationally the Copernican Principle of universal homogeneity and isotropy, as well as to probe various aspects of dark energy and dark matter through cross-correlations with other data such as the cosmic microwave or gamma-ray background. Last but not least, they constitute a test-bed for forthcoming wide-angle multi-million galaxy samples expected from such instruments as SKA, Euclid or LSST.