1999MNRAS.305..631A

Query : 1999MNRAS.305..631A

1999MNRAS.305..631A - Mon. Not. R. Astron. Soc., 305, 631-640 (1999/May-3)

The Lx-T relation and intracluster gas fractions of X-ray clusters.

ARNAUD M. and EVRARD A.E.

Abstract (from CDS):

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 <](δfgas fgas)2 >1/2 ≤ 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 fgas within spheres encompassing density contrasts δc=500 and 200 with respect to the critical density. Comparing binding mass estimates based on the virial theorem (VT) and the hydrostatic β-model (BM), we find a temperature-dependent discrepancy in fgas between the two methods caused by systematic variation of the outer slope parameter β with temperature. Mean values (for H0=50 km.s–1.Mpc–1) range from f-gas=0.10 for cool (T<4 keV) clusters using the VT at δc=500 to 0.22 for hot (T>4 keV) clusters using the BM at δc=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 LX-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.


Abstract Copyright: 1999 RAS

Journal keyword(s): galaxies: clusters: general - intergalactic medium - cosmology: observations - cosmology: theory - dark matter - X-rays: galaxies

Simbad objects: 24

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Number of rows : 24
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 ACO 262 ClG 01 52 50.4 +36 08 46           ~ 727 1
2 ACO 370 ClG 02 39 50.5 -01 35 08           ~ 825 0
3 2A 0251+413 ClG 02 54 26.6 +41 33 25           ~ 328 1
4 ACO 399 ClG 02 57 56.4 +13 00 59           ~ 420 0
5 ACO 401 ClG 02 58 50.3 +13 34 07           ~ 592 0
6 ACO 644 ClG 08 17 26.1 -07 31 13           ~ 241 0
7 ACO 665 ClG 08 30 45.2 +65 52 55           ~ 457 0
8 ACO 754 ClG 09 09 14.8 -09 40 35           ~ 695 1
9 NAME Hydra I Cluster ClG 10 36 36.0 -27 31 04           ~ 905 1
10 ACO 1367 ClG 11 44 44.6 +19 41 59           ~ 1127 1
11 ACO 1413 ClG 11 55 12.87 +23 23 46.9           ~ 456 0
12 NAME Virgo Cluster ClG 12 30 47.8 +12 23 07           ~ 7107 0
13 ACO 3526 ClG 12 48 49.2 -41 18 17           ~ 1154 2
14 ACO 1656 ClG 12 59 44.40 +27 54 44.9           ~ 5141 2
15 ACO 3558 ClG 13 28 03.2 -31 31 35           ~ 476 2
16 AWM 4 ClG 16 04 52.01 +23 56 26.9     14.38     ~ 141 0
17 ACO 2163 ClG 16 15 46.1 -06 08 50           ~ 586 0
18 ACO 2218 ClG 16 35 54.0 +66 13 00           ~ 827 1
19 BAX 249.5848-64.5165 ClG 16 38 13.2 -64 21 21           ~ 123 0
20 ACO 2256 ClG 17 03 37.5 +78 37 23           ~ 928 1
21 BAX 258.1082-23.3759 ClG 17 12 26.3 -23 21 38           ~ 303 0
22 ACO 2319 ClG 19 21 14.0 +43 56 57           ~ 495 1
23 ACO 3921 ClG 22 49 59.0 -64 25 48           ~ 165 1
24 ACO 2634 ClG 23 38 18.4 +27 01 37           ~ 515 2

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