Absorption of the CMB by hot gas in cluster is expected

Absorption of the CMB by hot gas in cluster is expected -...

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Absorption of the CMB by hot gas in cluster is expected (the Sunyaev-Zeldovich effect) and has been observed after years of upper limits - this is interesting as direct confirmation that we are not seeing some unknown local effect, since the CMB comes from behind clusters at substantial redshift. Note that the CMB temperature should scale as 1+z ; measurements of low-energy fine- structure levels (specifically C II * ) in QSO absorption-line systems indeed show this effect. As shown by Ge, Bechtold, and Black 1997 ApJ 474, 67, (courtesy of the AAS),
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Unformatted text preview: In retrospect, the first hint of the CMB was the excitation temperature of interstellar CN seen in absorption at 3874 against galactic stars, with observations tracing back to Adams 1941 (ApJ 93, 11; see Thaddeus 1972 ARA&A 10, 305 for a fuller history). As discussed by Roth, Meyer, and Hawkins (1993 ApJL 413, L67), these lines are excited by absorbing radiation at 1.3 and 2.6mm. These observations have some philosophical interest in showing the uniformity of this radiation on galactic scales....
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This note was uploaded on 11/10/2011 for the course AST AST1002 taught by Professor Emilyhoward during the Fall '10 term at Broward College.

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