ChaMP Serendipitous Galaxy Cluster Survey

We present a survey of serendipitous extended X-ray sources and optical cluster candidates from the Chandra Multiwavelength 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 deg 2 , 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 � 10 � 14 ergs cm � 2 s � 1 , with a median cluster core radius of 21 00 . For 56 of the 130 X-ray fields, we use the ChaMP’s deep NOAO 4 m MOSAIC g 0 , r 0 , and i 0 imaging to independently detect cluster candidates using a Voronoi tessellation and percolation (VTP) method. Red-sequence filtering decreases the galaxy fore- and background contamination and provides photometric redshifts to z � 0:7. From the overlapping 6.1 deg 2 X-ray/optical imaging, wefind115opticalclusters (ofwhich11%areintheX-raycatalog)and28X-rayclusters(ofwhich46%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 LX ¼ 2:65 � 0:19 ðÞ ; 10 43 ergs s � 1 . The clusters in our sample that are only detected in our optical data are poorer on average (� 4 � ) than the X-ray/optically matched clusters, which may partially explain the difference in the detection fractions. Subject headingg galaxies: clusters: general — surveys — X-rays: galaxies: clusters