NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-04-22 T18:19:19 PDT
Help | Comment | NED Home

For refcode 2000MNRAS.311..825W:
Retrieve 27 NED objects in this reference.
Please click here for ADS abstract

NED Abstract

Copyright by Royal Astronomical Society. 2000MNRAS.311..825W Constraints on the asymptotic baryon fractions of galaxy clusters at large radii Xiang-Ping Wu and Yan-Jie Xue Accepted 1999 September 10. Received 1999 August 13; in original form 1999 June 28 ABSTRACT While X-ray measurements have so far revealed an increase in the volume- averaged baryon fractions f_b_(r) of galaxy clusters with cluster radii r, f_b_(r) should asymptotically reach a universal value f_b_({infinity})= f_b_, provided that clusters are representative of the Universe. In the framework of hydrostatic equilibrium for intracluster gas, we have derived the necessary conditions for f_b_({infinity})= f_b_. The X-ray surface brightness profile described by the {beta} model and the temperature profile approximated by the polytropic model should satisfy {gamma} ~2(1- 1/3{beta}) and {gamma} ~1+1/3{beta} for {beta} < 1 and {beta} > 1, respectively, which sets a stringent limit to the polytropic index: {gamma} < 4/3. In particular, a mildly increasing temperature with radius is required if the observationally fitted {beta} parameter is in the range 1/3<{beta}<2/3. It is likely that a reliable determination of the universal baryon fraction can be achieved in the small {beta} clusters because the disagreement between the exact and asymptotic baryon fractions for clusters with {beta}>2/3 breaks down at rather large radii (>~30rc) where hydrostatic equilibrium has probably become inapplicable. We further explore how to obtain the asymptotic value f_b_({infinity}) of the baryon fraction from the X-ray measurement made primarily over the finite central region of a cluster. We demonstrate our method using a sample of 19 strong lensing clusters, which enables us to place a useful constraint on f_b_({infinity}):0.094+/-0.035<= f_b_({infinity})<=0.41+/-0.18, corresponding to a cosmological density parameter 0.122+/-0.069<={OMEGA}_M_ <= 0.53+/-0.28 for H_0_ = 50 km s^-1^ Mpc^-1^. An optimal estimate of f_b_({infinity}) based on three cooling flow clusters with b<1/2 in our lensing cluster sample yields <f_b_({infinity})> = 0.142+/-0.007 or {OMEGA}_M_ = 0.35+/-0.09. Keywords: galaxies: clusters: general - intergalactic medium - cosmology: theory - X-rays: galaxies
Retrieve 27 NED objects in this reference.
Please click here for ADS abstract

Back to NED Home