Modeling Intracluster Gas in Triaxial Dark Halos: An Analytic Approach

We present the first physical model for the non-spherical intra-cluster gasdistribution in hydrostatic equilibrium under the gravity of triaxial darkmatter halos. Adopting the concentric triaxial density profiles of the darkhalos with constant axis ratios proposed by Jing & Suto (2002), we derive ananalytical expression for the triaxial halo potential on the basis of theperturbation theory, and find the hydrostatic solutions for the gas density andtemperature profiles both in isothermal and polytropic equations of state. Theresulting iso-potential surfaces are well approximated by triaxial ellipsoidswith the eccentricities dependent on the radial distance. We also find aformula for the eccentricity ratio between the intra-cluster gas and theunderlying dark halo. Our results allow one to determine the shapes of theunderlying dark halos from the observed intra-cluster gas through the X-rayand/or the Sunyaev-Zel'dovich effects clusters.Comment: accepted by ApJ, LaTex file, 22 pages, 8 postscript figure