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| Title: | The L-X-T relation and intracluster gas fractions of X-ray clusters |
| Authors: | Arnaud, M
Evrard, AE |
| Keywords: | galaxies : clusters : general
intergalactic medium
cosmology : observations
cosmology : theory
dark matter
X-rays : galaxies |
| Issue Date: | 21-May-1999 |
| Publisher: | Blackwell Science Ltd |
| Citation: | Arnaud, M; Evrard, AE. (1999). Monthly Notices of the Royal Astronomical Society, 305:(3) 631-640. <http://hdl.handle.net/2027.42/60634> |
| Abstract: | We re-examine the X-ray luminosity-temperature relation using a nearly homogeneous data set of 24 clusters selected for statistically accurate temperature measurements and absence of strong cooling flows. The data exhibit a remarkably tight power-law relation between bolometric luminosity and temperature with a slope 2.88 +/- 0.15. With reasonable assumptions regarding cluster structure, we infer an upper limit on fractional variations in the intracluster gas fraction [(delta f(gas)/f(gas))(2)](1/2) less than or equal to 15 per cent. A strictly homogeneous Ginga subset of 18 clusters places a more stringent limit of 9 per cent. Imaging data from the literature are employed to determine absolute values of f(gas) within spheres encompassing density contrasts delta(c) = 500 and 200 with respect to the critical density. Comparing binding mass estimates based on the virial theorem (VT) and the hydrostatic beta-model (BM), we find a temperature-dependent discrepancy in f(gas) between the two methods caused by systematic variation of the outer slope parameter beta with temperature. Mean values (for H-0 = 50 km s(-1) Mpc(-1)) range from (f) over bar(gas) = 0.10 for cool (T < 4 keV) clusters using the VT at delta(c) = 500 to 0.22 for hot (T > 4keV) clusters using the BM at delta(c) = 200. There is evidence that cool clusters have a lower mean gas fraction than hot clusters, but it is not possible to assess the statistical significance of this effect in the present data set. The T dependence of the intracluster medium (ICM) density structure, coupled with the increase of the gas fraction with T in the VT approach, explains the steepening of the L-X-T relation. The small variation about the mean gas fraction within this majority subpopulation of clusters presents an important constraint for theories of galaxy formation and supports arguments against an Einstein-de Sitter universe based on the population mean gas fraction and conventional, primordial nucleosynthesis. The apparent trend of lower gas fractions and more extended atmospheres in low-temperature systems is consistent with expectations of models incorporating the effects of galactic winds on the ICM. |
| URI: | http://arxiv.org/abs/astro-ph/9806353 |
| ISSN: | 0035-8711 |
| Appears in Collections: | Astrophysics (Physics, Department of)
Interdisciplinary and Peer-Reviewed
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| ArnaudEvrard1998LxTRelation.pdf | | 270Kb | Adobe PDF | View/Open |
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