We present a survey of serendipitous extended X-ray sources and optical cluster candidates from the Chandra Multi-wavelength Project ( ChaMP ) .
Our main goal is to make an unbiased comparison of X-ray and optical cluster detection methods .
In 130 archival Chandra pointings covering 13 square degrees , we use a wavelet decomposition technique to detect 55 extended sources , of which 6 are nearby single galaxies .
Our X-ray cluster catalog reaches a typical flux limit of about \sim 10 ^ { -14 } erg s ^ { -1 } cm ^ { -2 } , with a median cluster core radius of 21″ .
For 56 of the 130 X-ray fields , we use the ChaMP ’ s deep NOAO/4m MOSAIC g ^ { \prime } , r ^ { \prime } , and i ^ { \prime } imaging to independently detect cluster candidates using a Voronoi tessellation and percolation ( VTP ) method .
Red-sequence filtering decreases the galaxy fore/background contamination and provides photometric redshifts to z \sim 0.7 .
From the overlapping 6.1 square degree X-ray/optical imaging , we find 115 optical clusters ( of which 11 % are in the X-ray catalog ) and 28 X-ray clusters ( of which 46 % are in the optical VTP catalog ) .
The median redshift of the 13 X-ray/optical clusters is 0.41 , and their median X-ray luminosity ( 0.5-2 keV ) is L _ { X } = ( 2.65 \pm 0.19 ) \times 10 ^ { 43 } ~ { } \mbox { ergs } ~ { } \mbox { s } ^ { -1 } .
The clusters in our sample that are only detected in our optical data are poorer on average ( \sim 4 \sigma ) than the X-ray/optically matched clusters , which may partially explain the difference in the detection fractions .