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The optical fiber integral field unit (IFU) built to feed the near infrared (NIR) spectrograph for the 11-meter Southern African Large Telescope (SALT) has undergone prototyping and rigorous performance testing at Wash- burn Astronomical Laboratories of the University of Wisconsin-Madison Astronomy Department. The 43 m length of 256 fibers which make up the object and sky arrays and spares are routed from the SALT payload down into the spectrograph room in four separate cables. The IFU covers 344 arcsec2 on the sky, with the object array spanning a 552 arcsec2 near-rectangular area at roughly 56% fill-factor. Companion papers describe the mechanical design of the fiber cable that mitigates potential sources of mechanical strain on the optical fiber (Smith et al.) and details of the spectrograph (Wolf et al.). Here we present the results of the performance testing of various test cables as well as performance testing and end-to-end mapping of the fully-assembled science cable. The fiber optics experience an extreme temperature gradient at the ingress to the instrument enclosure held at -40 ◦C during operation. We find an increase in focal ratio degradation (FRD) when holding progressively longer lengths of test fiber at reduced temperature. However, we confirm that this temperature dependent FRD is negligible for our designed length of cold fiber. We also find negligible contributions to FRD from the rubber seal that breaches the room temperature strain relief box and the cold instrument enclosure. Our measure- ments characterize performance including the effects of internal fiber inhomogeneities, stress induced from fiber handling and termination, as well as any imperfections from end-polishing. We present the room-temperature laboratory performance measurements of the fully-assembled science cable; the effective total throughput the fiber cable delivers to the spectrograph collimator is 81±2.5% across all fibers accounting for all losses. 

Abstract In the local universe, OH megamasers (OHMs) are detected almost exclusively in infrared-luminous galaxies, with a prevalence that increases with IR luminosity, suggesting that they trace gas-rich galaxy mergers. Given the proximity of the rest frequencies of OH and the hyperfine transition of neutral atomic hydrogen (Hi), radio surveys to probe the cosmic evolution of Hiin galaxies also offer exciting prospects for exploiting OHMs to probe the cosmic history of gas-rich mergers. Using observations for the Looking At the Distant Universe with the MeerKAT Array (LADUMA) deep Hisurvey, we report the first untargeted detection of an OHM atz> 0.5, LADUMA J033046.20−275518.1 (nicknamed “Nkalakatha”). The host system, WISEA J033046.26−275518.3, is an infrared-luminous radio galaxy whose optical redshiftz≈ 0.52 confirms the MeerKAT emission-line detection as OH at a redshiftz_OH= 0.5225 ± 0.0001 rather than Hiat lower redshift. The detected spectral line has 18.4σpeak significance, a width of 459 ± 59 km s⁻¹, and an integrated luminosity of (6.31 ± 0.18 [statistical] ± 0.31 [systematic]) × 10³L_⊙, placing it among the most luminous OHMs known. The galaxy’s far-infrared luminosityL_FIR= (1.576 ±0.013) × 10¹²L_⊙marks it as an ultraluminous infrared galaxy; its ratio of OH and infrared luminosities is similar to those for lower-redshift OHMs. A comparison between optical and OH redshifts offers a slight indication of an OH outflow. This detection represents the first step toward a systematic exploitation of OHMs as a tracer of galaxy growth at high redshifts.