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New Planck maps reveal unseen details throughout the Milky Way

February 16, 2012

An unambiguous detection of the Galactic Haze – a mysterious, diffuse emission from the central portion of the Milky Way – and the first all-sky map of carbon monoxide, whose emission traces the molecular clouds where stars are born, are among the results being presented by the Planck Collaboration at an international conference held from 13 to 17 February 2012, in Bologna, Italy. These results have been achieved during the complex task of identifying and removing the foreground contamination due to Galactic and extragalactic emission that obscures the Cosmic Microwave Background.

All-sky image of molecular gas and three molecular cloud complexes seen by Planck. Source: ESA/Planck Collaboration)

The primary goal of ESA's Planck satellite is to observe the Cosmic Microwave Background (CMB), the relic radiation from the Big Bang, and to measure its tiny fluctuations across the sky with unprecedented accuracy. These variations contain all-important information about the constituents of the Universe and the origin of cosmic structure. Along with the CMB, Planck also sees almost every bright source that shone throughout cosmic history. This includes emission from individual galaxies and, most notably, from the interstellar medium (ISM) in our Galaxy, the Milky Way. Diffuse emission from this mixture of gas and dust represents the dominant source of foreground contamination to the CMB at all frequencies of interest across the entire plane of our Galaxy.

A careful and complex process of data 'cleaning' is necessary to peel away the 'layers' of foreground emission in order to access the CMB's rich reservoir of cosmological information. Removing these layers reveals a wealth of data that is crucial for many other fields in astronomy. In particular, new facets of the Milky Way's diffuse emission and of its large-scale distribution of stellar nurseries are unveiled in two new all-sky images that are being presented at the conference "Astrophysics from the radio to submillimetre – Planck and other experiments in temperature and polarization" held from 13 to 17 February 2012 in Bologna, Italy.

"The lengthy and delicate task of foreground removal provides us with excellent data sets that are being used to shed new light on several hot topics in Galactic and extragalactic astronomy," comments Jan Tauber, Planck Project Scientist at ESA. "In the recent past we have made important strides with Planck in understanding the properties of some previously poorly constrained components of our Galaxy, and this week we present new results revealing other intriguing players in the microwave sky. Together, they show that Planck is providing important new information to our picture of the Milky Way and the Universe at large," he adds.

"We now have a 'treasure map' of previously unknown islands of molecular gas that we plan to explore with follow-up observations," notes François Boulanger from IAS, another Planck Collaboration scientist. Further studies will allow a detailed investigation of the physical and chemical conditions that lead to the formation of molecular clouds, shedding new light on the very early phases of star formation.

The results presented this week demonstrate that the collaboration is making great progress in identifying and isolating all contributions to the foreground emission. "These results show how well Planck is working, and how well we can do this "foreground cleaning". We now look forward to the information that we will be able to extract from the "background" itself, where we will learn about the properties of the Universe," explains Douglas Scott, scientist with the Canadian team.

Canada participated in the development of the LFI and HFI, the two instruments on Planck, mainly through development of the rapid interpretation software and the real-time analysis software that will make it possible to verify the data in the preliminary stages of the mission. The data analysis software for the LFI and HFI were developed in parallel by two teams, one at the University of British Columbia and one at the University of Toronto, both funded by the Canadian Space Agency. Canadian scientists are also heavily engaged in all aspects of analysis of the data and its scientific interpretation.

Professor Douglas Scott of the University of British Columbia is leading the Canadian LFI team. The HFI team is led by Professor J. Richard Bond of the University of Toronto. The Canadian teams have spent more than a decade working with their international colleagues to plan for the Planck mission, and will be directly involved in using the data to answer some of the biggest questions in the Universe.

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