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A Multiphase Model for the Intracluster Medium | | D. Nagai
; M.E. Sulkanen
; A.E. Evrard
; | | Date: |
19 Mar 1999 | | Journal: | Mon.Not.Roy.Astron.Soc. 316 (2000) 120 | | Subject: | astro-ph | | Abstract: | Constraints on the clustered mass density Omega_m of the universe derived from the mean intracluster gas fraction of X-ray clusters may be biased by 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 radially dependent variance sigma^2(r)=sigma_c^2 (1+r^2/r_c^2)^{-eps}. 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 {sigma_c,eps} 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 in the {sigma_c,eps} plane. From these parameters, the correct value of mean ICM gas fraction 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, ltsim 20%. | | Source: | arXiv, astro-ph/9903308 | | Services: | Forum | Review | PDF | Favorites | |
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