Astronomy and Astrophysics – Astronomy
Scientific paper
Apr 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999head....4.0410n&link_type=abstract
American Astronomical Society, HEAD meeting #4, #04.10; Bulletin of the American Astronomical Society, Vol. 31, p.701
Astronomy and Astrophysics
Astronomy
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 constant (radially independent) density fluctuations thoughout the ICM. Fixing the x-ray emission and emission weighted temperature, we explore two independently observable signatures of the model in the \{sigma_c ,epsilon \} space. For bremsstrahlung dominated emission, the central Sunyaev-Zel'dovich (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 \{hat σ_c,hat ɛ\} in the model space. From these parameters, the correct value of < fICM > in the multiphase model results, allowing an unbiased estimate of Omega_m to be recovered.
Evrard August E.
Nagai Daisuke
Sulkanen Martin E.
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