We present a catalog of galaxy clusters detected in a new ROSAT PSPC survey .
The survey is optimized to sample , at high redshifts , the mass range corresponding to T > 5 keV clusters at z = 0 .
Technically , our survey is the extension of the 160 square degrees survey ( 160d , ) .
We use the same detection algorithm , thus preserving high quality of the resulting sample ; the main difference is a significant increase in sky coverage .
The new survey covers 397 square degrees and is based on 1610 high Galactic latitude ROSAT PSPC pointings , virtually all pointed ROSAT data suitable for the detection of distant clusters .
The search volume for X-ray luminous clusters within z < 1 exceeds that of the entire local Universe ( z < 0.1 ) .
We detected 287 extended X-ray sources with fluxes f > 1.4 \times 10 ^ { -13 } erg s ^ { -1 } cm ^ { -2 } in the 0.5–2 keV energy band , of which 266 ( 93 % ) are optically confirmed as galaxy clusters , groups or individual elliptical galaxies .
This paper provides a description of the input data , the statistical calibration of the survey via Monte-Carlo simulations , and the catalog of detected clusters .
We also compare the basic results to those from previous , smaller area surveys and find good agreement for the \log N – \log S distribution and the local X-ray luminosity function .
Our sample clearly shows a decrease in the number density for the most luminous clusters at z > 0.3 .
The comparison of our ROSAT -derived fluxes with the accurate Chandra measurements for a subset of high-redshift clusters demonstrates the validity of the 400 square degree survey ’ s statistical calibration .