The k-band hubble diagram for brightest cluster galaxies in x-ray clusters

Dec, 1997
15 pages
Published in:
  • Mon.Not.Roy.Astron.Soc. 297 (1998) 128
e-Print:
Report number:
  • ICAST-97-16

Citations per year

199920042009201420180246810
Abstract: (arXiv)
This paper concerns the K band Hubble diagram for the brightest cluster galaxies (BCGs) in a sample of X-ray clusters covering the redshift range 0.05<z<0.80.05<z<0.8. We show that BCGs in clusters of high X-ray luminosity are excellent standard candles: the intrinsic dispersion in the raw K band absolute magnitudes of BCGs in clusters with LX>2.3×1044L_{\rm X} > 2.3 \times 10^{44} erg s1^{-1} (in the 0.3 - 3.5 keV band) is no more than 0.22 mag, and is not significantly reduced by correcting for the BCG structure parameter, α\alpha, or for X-ray luminosity. This is the smallest scatter in the absolute magnitudes of any single class of galaxy and demonstrates the homogeneity of BCGs in high-LXL_{\rm X} clusters. By contrast, we find that the brightest members of low-LXL_{\rm X} systems display a wider dispersion (0.5\sim 0.5 mag) in absolute magnitude than commonly seen in previous studies, which arises from the inclusion, in X-ray flux-limited samples, of poor clusters and groups which are usually omitted from low redshift studies of BCGs in optically rich clusters....[abstract shortened].. The BCGs in our high-LXL_{\rm X} clusters yield a value of ΩM=0.28±0.24\Omega_{\rm M}=0.28\pm0.24 if the cosmological constant Λ=0\Lambda=0. For a flat Universe we find ΩM=0.550.15+0.14\Omega_{\rm M}=0.55^{+0.14}_{-0.15} with a 95 per cent confidence upper limit to the cosmological constant corresponding to ΩΛ<0.73\Omega_{\Lambda}<0.73. These results are discussed in the context of other methods used to constrain the density of the Universe, such as Type Ia supernovae.