Long-term variability of extragalactic radio sources in the Planck Early Release Compact Source Catalogue

Understand

Combining measurements taken using the Wilkinson Microwave Anisotropy Probe (WMAP) from 2001 to 2008 with measurements taken using Planck from 2009 to 2010, we investigate the long-term flux density variability of extragalactic radio sources selected from the Planck Early Release Compact Source Catalogue.

• The single-year, single-frequency WMAP maps are used to estimate yearly-averaged flux densities of the sources in the four WMAP bands: Ka (33 GHz), Q (41 GHz), V (61 GHz), and W (94 GHz).
• We identify 82, 67, 32, and 15 sources respectively as variable at greater than 99% confidence level in these four bands.
• The amplitudes of variation are comparable between bands, and are not correlated with either the flux densities or the spectral indices of the sources.