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By re-reducing data contained in the ROSAT All-Sky Survey, of an area including the 2 degree Field Galaxy Redshift Survey (2dFGRS), Jasmina Lazendic-Galloway, Amelia Fraser-McKelvie and Kevin Pimbblet (in the photo) have discovered some of the missing baryonic (protons, neutrons and electrons) mass in the local Universe.
Theories of structure formation in the Universe, in fact, predict the existence of a certain amount of mass in the form of very hot (around 1 million degrees), low density gas in filamentary structures that join galaxy clusters.
Despite years of work, and the knowledge that the high temperatures would make this matter emit at X-ray wavelengths, no-one had ever managed to produce a detection of the filaments of sufficient quality to estimate their properties (mass, density, temperature, luminosity, etc.).
Until now, only numerical simulations provided hints to these values.
However, the 22-year old undergraduate student, Amelia Fraser-McKelvie, at the School of Physics at Monash University (Australia), during a summer internship, has done just this. Working with Jasmina Lazendic-Galloway (X-ray astronomy expert) and Kevin Pimbblet (lecturer and co-author of a catalogue of galaxy filaments) Fraser-McKelvie added the signal from many filaments to detect the emission in the ROSAT images that had gone unnoticed until now.
The research focused on a sample of 41 galaxy filaments, thought to be representative of the structures in the Universe at large, and measured their average X-ray flux and estimated their average electron density.
Lazendic-Galloway and Pimbblet then did the rest, although they would admit that quantifying the amount of missing mass actually found is very difficult from their present data. The final results will be published in the Monthly Notices of the Royal Astronomical Society, to the great satisfaction of the young student.
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