Is MS 1054-03 an Exceptional Cluster? A New Investigation of ROSAT HRI X-Ray Data
Abstract
We reanalyzed the ROSAT HRI observation of MS 1054-03, optimizing the channel HRI selection and including a new exposure of 68 ks. From a wavelet analysis of the HRI image we identify the main cluster component and find evidence for substructure in the west, which might be either a group of galaxies falling onto the cluster or a foreground source. Our one- and two-dimensional analysis of the data show that the cluster can be fitted well by a classical β model centered only 20" away from the central cD galaxy. The core radius and β values derived from the spherical model (β=0.96+0.48-0.22) and the elliptical model (β=0.73+/-0.18) are consistent. We derived the gas mass and total mass of the cluster from the β-model fit and the previously published ASCA temperature (12.3+3.1-2.2 keV). The gas mass fraction at the virial radius is fgas=(14[-3,+2.5]+/-3)% for Ω0=1, where the errors in square brackets come from the uncertainty on the temperature, and the remaining errors from the HRI imaging data. The gas mass fraction computed for the best-fit ASCA temperature is significantly lower than found for nearby hot clusters, fgas=(20.1+/-1.6)%. This local value can be matched if the actual virial temperature of MS 1054-03 were close to the lower ASCA limit (~10 keV), with an even lower value of 8 keV giving the best agreement. Such a bias between the virial and measured temperature could be due to the presence of shock waves in the intracluster medium, stemming from recent mergers. Another possibility, which reconciles a high temperature with the local gas mass fraction, is the existence of a nonzero cosmological constant.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 2000
- DOI:
- 10.1086/309546
- arXiv:
- arXiv:astro-ph/0005350
- Bibcode:
- 2000ApJ...542...35N
- Keywords:
-
- Cosmology: Observations;
- Cosmology: Dark Matter;
- Galaxies: Clusters: Individual: Alphanumeric: MS 1054-03;
- X-Rays: Galaxies;
- Astrophysics
- E-Print:
- 12 pages, 5 figures, accepted for publication in ApJ