Astronomy and Astrophysics – Astrophysics
Scientific paper
1999-08-10
Astronomy and Astrophysics
Astrophysics
11 pages LaTeX, 3 figures (one colour), submitted to Pub. Ast. Soc. Aus., substantially revised and enlarged
Scientific paper
Several lines of evidence suggest that cold, dense gas clouds make a substantial contribution to the total mass of dark halos. If so then physical collisions between clouds must occur; these cause strong, radiative shocks to propagate through the cold gas, with the startling implication that all ``dark'' halos must be luminous. The expected luminosity is a strong function of halo velocity dispersion, and should contribute a significant fraction of the observed X-ray emission from clusters of galaxies, if dark halos are predominantly made of cold gas. Existing data do not exclude this possibility; indeed two particular expectations of the luminous-halo model are borne out in the X-ray data, and thus give support to the cold-cloud dark matter model. First we find a luminosity-temperature correlation of the form L proportional to T to the power 11/4, as seen in recent analyses of cluster samples. Secondly the anticipated spectra have substantially more power at low energies than isothermal bremsstrahlung spectra, and might account for the observed ``excess'' EUV emission seen from some clusters. The successes of the luminous-halo model are particularly remarkable because the theory has no free parameters or ad hoc elements. The model can be tested by the X-ray satellite Chandra, which should resolve the Virgo cluster into 10,000 point-like, transient X-ray sources. Non-detection of any such sources by Chandra can constrain the contribution of cold gas clouds to below 1% of the total matter density in the Universe, assuming Virgo to be representative.
No associations
LandOfFree
Luminous "Dark" Halos does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Luminous "Dark" Halos, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Luminous "Dark" Halos will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-201873