An estimate of the electron density in filaments of galaxies at z similar to 0.1

• Published in: Monthly notices of the Royal Astronomical Society 2011-08, Vol.415 (2), p.1961-1966
• Main Authors: Fraser-McKelvie, Amelia, Pimbblet, Kevin A, Lazendic, Jasmina S
• Format: Article
• Language: English
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1111/j.1365-2966.2011.18847.x

Most of the baryons in the Universe are thought to be contained within filaments of galaxies, but as yet, no single study has published the observed properties of a large sample of known filaments to determine typical physical characteristics such as temperature and electron density. This paper presents a comprehensive large-scale search conducted for X-ray emission from a population of 41 bona fide filaments of galaxies to determine their X-ray flux and electron density. The sample is generated from the filament catalogue of Pimbblet et al., which is in turn sourced from the two-degree Field Galaxy Redshift Survey (2dFGRS). Since the filaments are expected to be very faint and of very low density, we used stacked ROSAT All-Sky Survey data. We detect a net surface brightness from our sample of filaments of (1.6 +/- 0.1) 10-14ergcm-2s-1arcmin -2 in the 0.9-1.3keV energy band for 1-keV plasma, which implies an electron density of ne= (4.7 +/- 0.2) 10-4