Other
Scientific paper
May 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999aas...194.8902n&link_type=abstract
American Astronomical Society, 194th AAS Meeting, #89.02; Bulletin of the American Astronomical Society, Vol. 31, p.981
Other
Scientific paper
Constraints on the clustered mass density Omega_m of the universe derived from the observed population mean intracluster gas fraction < fICM > of X-ray clusters may be biased by reliance on a single-phase assumption for the thermodynamic structure of the intracluster medium (ICM). We propose a descriptive model for multiphase structure in which a spherically symmetric ICM contains isobaric density perturbations with a radially dependent variance sigma (2(r)) = sigma_c (2) (1+r(2/r_c^2)(-epsilon )) . The model extends the work of Gunn & Thomas (1996) which assumed radially independent density fluctuations thoughout the ICM. Fixing the X-ray emission profile and emission weighted temperature, we explore two independently observable signatures of the model in the the model in the {sigma_c ,epsilon } space. For bremsstrahlung dominated emission, the central Sunyaev--Zeldovich (SZ) decrement in the multiphase case is increased over the single-phase case and multiphase X-ray spectra in the range 0.1-20 keV are flatter in the continuum and exhibit stronger low energy emission lines than their single-phase counterpart. We quantify these effects for a fiducial 10(8) K cluster and demonstrate how the combination of SZ and X-ray spectroscopy can be used to identify a preferred location σ_c,hat ɛ in the model plane. From these parameters, the correct value of < fICM > in the multiphase model results, allowing an unbiased estimate of Omega_m to be recovered. The consistency of recent determinations of the Hubble constant from SZ and X-ray observations with values determined by other methods suggests that biases in ICM gas fractions are small, <~ 20%.
Evrard August E.
Nagai Daisuke
Sulkanen Martin
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