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4 Discussion and conclusions

For A 1300 we have measured the temperature in two concentric regions, divided so as to give comparable numbers of source photons: an inner circle of size comparable with that of the PSF (radius 3') and the surrounding annulus. Both sub-regions show temperatures compatible with the whole region, but with larger uncertainties. Thus, the question of a temperature gradient in A 1300, as suggested by the PSPC observation, remains open, since the cluster is not well resolved by ASCA and its flux is too weak to attempt any spatial/energy deconvolution.

We have also investigated the presence of a power-law contribution to the X-ray emission from A 1300, possibly associated with the radio halo. The spectral fitting, however, did not yield any conclusive results (no improvement in $\chi^{2}$) nor a useful limit to such a non-thermal contribution.

A 1300 has rather a low metal abundance ($\sim 0.17 \pm 0.1 $solar). This, taken with its high temperature and luminosity, fits well into the post-merger picture sketched by Lémonon et al. (1997). The cluster was shown to be quite extended with a flat luminosity distribution -- suggesting that the merging entities have not yet reached the state of a virialized cluster -- and thus, the elapsed time has been too short for a cooling flow to form. This is in agreement with Allen & Fabian (1998) showing that high z non-cooling flow clusters tend to have lower metallicities ($\sim 0.2$) than cooling flow clusters.

Mushotzky & Scharf (1997) and Tsuru (1998) have shown that there is no significant change in the $L_{\rm X
 Bol}-T_{\rm X}$ relation out to $z \sim 0.4-0.6$ and our present data points are well within the overall distribution. A similar agreement (within 2 sigma of the mean correlation) is also found between the Mushotzky & Scharf $\sigma_{\rm v}-T_{\rm X}$ correlation and our findings.

The ASCA analysis of A 1300 and A 1732 provides new data on medium-distant galaxy clusters. Their overall properties appear to follow the general trends, which show no evolution but a rather large scatter related to the various virialization stages present in the cluster population. In a forthcoming paper (Lémonon et al. 1999) we shall discuss in more detail the properties of these clusters and of their galaxy content in connection with observations in the infrared, optical and radio bands.


This work results from an ESA/ISAS collaboration based on the ASCA space programme. M.P. is grateful to the Centre National d'Études Spatiales for a "Sol et Espace" grant and enjoyed the hospitality at Kyoto University of the Cosmic Ray Group led by Pr. Koyama for two weeks in September 1997.

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