The L X ‐ T Relation and Temperature Function for Nearby Clusters Revisited

Abstract

The X-ray luminosityÈtemperature relation for nearby T ^3.5È10 keV clusters is rederived using new ASCA temperatures and ROSAT luminosities. Both quantities are derived by directly excluding the cooling Ñow regions. This correction results in a greatly reduced scatter in the Ñow clusters are similar to others outside the small cooling Ñow regions. For a Ðt of the form L bolPT a, L X-T relation; cooling we obtain a\2.64^0.27 (90%) and a residual rms scatter in log L bol of 0.10. The derived relation can be directly compared to theoretical predictions that do not include radiative cooling. It also provides an accurate reference point for future evolution searches and comparison to cooler clusters. The new tem- peratures and perature function at zD0.05. The resulting function is generally higher and Ñatter than, although within L X-T relation together with a newly selected cluster sample are used to update the tem- the errors of, the previous estimates by Edge and coworkers and Henry and Arnaud (as rederived by Eke and coworkers). For a qualitative estimate of constraints that the new data place on the density Ñuctuation spectrum, we apply the Press-Schechter formalism for cluster isothermality, the temperature function implies p8\0.55^0.03, while taking into account the )0\1 and 0.3. For )0\1, assuming observed cluster temperature proÐles, p8\0.51^0.03, consistent with the previously derived range. The dependence of on is di†erent from the earlier results because of our treatment of the slope of the Ñuctuation spectrum, n, as a free parameter. For the considered values of p8 )0 ) n\[(2.0È2.3)^0.3, somewhat steeper than that derived from the earlier temperature function data, in agreement with the 0, local slope of the galaxy Ñuctuation spectrum from the Automatic Plate Measuring Facility (APM) survey, and signiÐcantly steeper than the standard cold dark matter prediction.