On the Structure of Hot Gas in Halos: Implications for the Lx-Tx Relation & Missing Baryons

摘要: We present one-dimensional models of the hot gas in dark-matter halos, which both predict existence cool cores and explain their structure. Our are directly applicable to semi-analytic (SAMs) galaxy formation. have previously argued that filaments cold (~10^4 K) condense out intracluster medium (ICM) hydrostatic thermal equilibrium when ratio instability timescale free-fall time $t_{TI}/t_{ff}$ falls below 5-10. This criterion corresponds an upper limit on density ICM motivates a model core forms wherever $t_{TI}/t_{ff} \lesssim 10$. Consistent with observations numerical simulations, this predicts larger more tenuous for lower-mass halos---while cluster may be as large ~ 0.1 cm^{-3}, Galactic halo should not exceed 10^{-4} cm^{-3}. can also densities smaller mass halos (galactic `coronae') if we include contribution central gravitational potential. produce favorable match observational X-ray luminosity-temperature (Lx-Tx) relation. For masses $\lesssim 10^{13}$ Msun size approaches virial radius. Thus, most baryons such cannot ICM, but either form stars or beyond Because much available star formation, majority low ($\lesssim Msun) expelled radius due supernova feedback. account `missing' from halo.