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ABSTRACT In this paper we study large-scale structures and their galaxy content around the most X-ray luminous cluster known, RX J1347.5−1145 at z= 0.45. We make use of u* g′ r′ i′ z′ Canada-France-Hawaii Telescope (CFHT) MegaCam photometry together with VIsible MultiObject Spectrograph (VIMOS) Very Large Telescope (VLT) spectroscopy to identify structures around RX J1347 on a scale of ∼20 × 20 Mpc2. We construct maps of the galaxy distribution and the fraction of blue galaxies. We study the photometric galaxy properties as a function of the environment traced by the galaxy density. We identify group candidates based on galaxy overdensities and study their galaxy content. We also use available Galaxy Evolution Explorer ( GALEX) near-ultraviolet imaging to identify strong unobscured star-forming galaxies. We find that the large-scale structure around RX J1347 extends in the north-east-south-west direction for at least 20 Mpc, over a region in which most of the group candidates are located, some of which show X-ray emission in archival XMM-Newton observations. As in other studies, we find that the fraction of blue galaxies ( Fblue) is a function of galaxy number density, but the bulk of the trend is due to galaxies belonging to massive systems. The fraction of ultraviolet- (UV-) bright galaxies is also a function of environment, but their relative number compared with the blue population seems to be constant regardless of the environment. These UV emitters also have similar properties at all galaxy densities, indicating that the transition between galaxy types occurs over short time-scales. Candidate galaxy groups show a large variation in their galaxy content and Fblue in those groups displays little dependence on galaxy number density. This may indicate possible differences in their evolutionary status, or suggest that the processes acting in groups are different from those in clusters. The large-scale structure around rich clusters provides a dynamic environment for galaxy evolution. In the case of RX J1347, the transformation may start within infalling groups and finish with the removal of the cold gas once galaxies are accreted into massive systems. [ABSTRACT FROM AUTHOR]

The Atacama pathfinder experiment Sunyaev-Zel'dovich (APEX-SZ) instrument is a millimeter-wave cryogenic receiver designed to observe galaxy clusters via the Sunyaev-Zel'dovich effect from the 12 m APEX telescope on the Atacama plateau in Chile. The receiver contains a focal plane of 280 superconducting transition-edge sensor (TES) bolometers instrumented with a frequency-domain multiplexed readout system. The bolometers are cooled to 280 mK via a three-stage helium sorption refrigerator and a mechanical pulse-tube cooler. Three warm mirrors, two 4 K lenses, and a horn array couple the TES bolometers to the telescope. APEX-SZ observes in a single frequency band at 150 GHz with 1′ angular resolution and a 22′ field-of-view, all well suited for cluster mapping. The APEX-SZ receiver has played a key role in the introduction of several new technologies including TES bolometers, the frequency-domain multiplexed readout, and the use of a pulse-tube cooler with bolometers. As a result of these new technologies, the instrument has a higher instantaneous sensitivity and covers a larger field-of-view than earlier generations of Sunyaev-Zel'dovich instruments. The TES bolometers have a median sensitivity of 890 [formula] (NEy of 3.5 × 10-4 [formula]). We have also demonstrated upgraded detectors with improved sensitivity of 530 [formula] (NEy of 2.2 × 10-4 [formula]). Since its commissioning in April 2007, APEX-SZ has been used to map 48 clusters. We describe the design of the receiver and its performance when installed on the APEX telescope. [ABSTRACT FROM AUTHOR]