A new measurement of the X-ray temperature function of clusters of galaxies

¹ Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany
² Department of Astronomy, University of Virginia, PO Box 3818, 530 McCormick Road, Charlottesville, VA 22903-0818, USA
³ Institute of Space and Astronautical Science, Yoshinodai 3-1-1, Sagamihara, Kanagawa 229-8510, Japan
⁴ Department of Physics, Toho University, Miyama, Funabashi, Chiba 274-8510, Japan

Corresponding author: Y. Ikebe, ikebe@mpe.mpg.de

Received: 7 June 2001
Accepted: 11 December 2001

Abstract

We present a newly measured X-ray temperature function of galaxy clusters using a complete flux-limited sample of 61 clusters. The sample is constructed with the total survey area of 8.14 steradians and the flux limit of ergs s^-1 cm^-2 in the 0.1–2.4 keV band. X-ray temperatures and fluxes of the sample clusters were accurately measured with ASCA and ROSAT data. The derived temperature function covers an unprecedentedly wide temperature range of 1.4–11 keV. By fitting these data with theoretically predicted temperature functions given by the Press-Schechter formalism together with a recent formation approximation and the CDM power spectrum, we obtained tight and individual constraints on and . We also employed the Formation-Epoch model in which the distribution in the formation epoch of clusters as well as the temperature evolution are taken into account, showing significantly different results. Systematics caused by the uncertainty in the mass-temperature relation are studied and found to be as large as the statistical errors.