Detecting Intracluster Gas Motion in Galaxy Clusters: Mock Astro-E2 Observations

• Published in: The Astrophysical journal 2005-10, Vol.631 (2), p.773-784
• Main Authors: Pawl, Andrew, Evrard, August E, Dupke, Renato A
• Format: Article
• Language: English
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/432608

We explore the detectability of bulk motions in the X-ray-emitting intracluster medium using a catalog of 1836 mock Astro-E2 observations of simulated clusters of galaxies. We generate high-resolution mock spectra for two observing strategies: a four-pointing mosaic and a single central pointing. Normalizing to 200 (400) photons in the iron K alpha region for the mosaic (central) study, we fit Poisson realizations of each simulated spectrum to a velocity-broadened isothermal plasma emission model. We confirm that the velocity characteristics (mean and dispersion) returned by the spectral fittings are unbiased measures of the emission-weighted values within the observed region, with scatter plus or minus 55 km s super(-1). The maximum velocity difference between mosaic element pairs Delta upsilon sub(max) has similar to 6% likelihood of being transonic ( Delta upsilon sub(max) greater than or equal to 0.5c sub(s)), and the likelihood falls steeply, p proportional to ( Delta upsilon sub(max)/c sub(s)) super(-4), at high Mach number. The velocity-broadening parameter sigma sub( upsilon ) from the central pointing fit exceeds the thermal value in 49% of the cases, with again a sigma upsilon super(-4) tail at large dispersion. We present as case studies the clusters that yield the strongest signal for each observing strategy.