For the last 3 years I was working in the field of observational cosmology. This is an exciting area of astronomy to study, thanks to the WMAP satellite which gathered enough data to sensitivity. Cosmologists nowdays talk about the dawn of the era of "precision cosmology". Much effort has been spent in determining the angular power spectrum of the primordial fluctuations in the Cosmic Microwave Background (or CMB for short) radiation.

The CMB

The ESA's Plack satellite, launched in May 2009, is set to measure this to unprecedented sensitivity. Alas, the CMB signal arriving to our telescopes from the farthest reaches of the universe has to get trough a sizable section of our own Milky Way galaxy. The Milky Way itself is buzzing with radiation and the CMB signal is contaminated with this so-called foreground "noise". One of the priorities is to map and understand foreground emission from our own Galaxy so that this signal could be subtracted form the total signal arriving to us, leaving the pure CMB signal. Knowing the spatial morphology of the foreground emission and the spectral shape of individual features is essential for the accurate subtraction of the foreground emission form the CMB signal. Equally interesting is to study foreground emission and individual sources in the Galactic plane as we can learn about the interstellar medium (ISM) and the life cycle of stars.

Galactic Foregrounds

The most interesting frequency range from the point of view of CMB observations is 30-200 GHz which overlaps with the minimum of the combined foregrounds emission at 70 GHz. The Galactic foregrounds include synchrotron, free-free and vibrational (thermal) dust emission and point sources that may be stars in the Galaxy or other galaxies. In recent years there is mounting evidence for the existence of another component that emits in the frequency range of 20-60 GHz, peaking at around 30 GHz. The new component is referred to as anomalous microwave emission. Figure 1 below shows the spectrum of the various foregrounds and the CMB anisotropy.

Figure 1: The combined foregrounds spectrum, taken from Davies et al. (2006), shows the components of the Galactic foreground emission.