Tuesday, November 13, 2012
IPAC Astronomy Lunch Seminar
Unveiling high redshift structures with Planck
Niraj Welikala, IAS
The Planck satellite, with its large wavelength coverage and all-sky survey, has a unique potential of systematically detecting the brightest and rarest submillimetre sources on the sky. I will present an original method based on a combination of Planck and IRAS data which we use to select the most luminous submillimetre high-redshift (z>1-2) cold sources over the sky. The majority of these sources are either individual, strongly lensed galaxies, or represent the combined emission of several submillimetre galaxies within the large beam of Planck. The latter includes, in particular, rapidly growing galaxy groups and clusters. I demonstrate the selection method on the first 4 confirmations that include a newly discovered over-density of 5 submillimetre-bright sources which has been confirmed with Herschel/SPIRE observations and followed up with ground-based observations including VLT/XSHOOTER spectroscopy. Using Planck, I also unveil the nature of 107 high-redshift lensed dusty star-forming galaxies that have been previously detected by the South Pole Telescope over 940 square degrees. As well as characterizing the few SPT galaxies that are detected individually by Planck, I stack the sources in the Planck maps to obtain mean properties (including redshift) of the galaxy sample. I will also discuss what sources contribute to the combined emission measured within the Planck beam. In particular, I show how stacking these high-redshift lensed galaxies in the Planck maps also enables us to probe the z~1 environments around the foreground lenses.