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Jun29-05, 10:02 AM
Sci Advisor
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Quote Quote by ohwilleke
Doesn't it follow that the absence of such blogs in the intra-culster medium, and to my knowledge they haven't been found, would, if not falisfying DM, at least, throw a spanner in the works?
Not necessarilly.

First, there have been a few (one?) cluster DM maps made (and the other name for the proposed LSST is 'Dark Matter Telescope' ), and they show much the same as what the (admittedly marginal) DM results from SZE observations, and X-ray profiles, show - a broad DM distribution, more or less centred on the cluster cD galaxy (or galaxies).

Second, AFAIK, no one has done this sort of thing (there is a paper that reports observations using PNe as tracers, for an NGC galaxy; they report 'no DM'. However, that was one galaxy, not ICM) ... and it would be quite a tour de force to pull such a study off.

Third, who knows what the ICM contains and how it is distributed and interacts (no Garth, not at the 1-10 Mpc level; at the 1 kpc level, or finer)? For example, look at all the structure which SDSS has turned up so far - streams, shredded globulars, LSB 'blobs', ... and look at what Subaru found when it took a deep look at a 'primordial' LG dwarf (all sorts of evidence of evolution), ... and what does the outskirts of M31 look like? ... and remember those outer 'shells' they found around ellipticals (what, 20 years ago now?) ...