11-02-2011: Colloquium Dorothea Samtleben
11 - 02 - 2011
Friday 11 February 2011, 11:00h, at Nikhef in H331
Speaker: Dorothea Samtleben (Nikhef)
Title: News from the oldest light
Measurements of the Cosmic Microwave Background Radiation (CMBR) temperature fluctuations have already provided rich information about the early Universe. By now the focus of CMBR experiments lies in measuring the much smaller CMBR polarization pattern which requires unprecedented sensitivity and control of systematics. The CMBR polarization pattern is commonly divided into E-modes which derive like its temperature anisotropies from density fluctuations in the early Universe and B-modes which are due to lensing by the mass in the line of sight but are also expected as signature of primordial gravity waves and with that provide unique access to the inflationary era in the very first moments of the Universe. While E-modes have already been detected it is only now that the sensitivity of upcoming experiments approaches the level where B-modes are expected.
I will present the first results from phase I of the ground-based Q/U Imaging ExperimenT (QUIET) from data taken 2008 to 2010 with coherent radiometer arrays of 19 (90) elements at 40 (90) GHz in the Atacama desert in Chile. We provide one of the best measurements of the E-mode power spectrum at degree angular scales together with one of the best upper limits on B-modes in that angular range. The results also demonstrate the extremely low systematics of this technique and with that its potential for future measurements from the ground to complement the upcoming measurements by Planck.
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