The NIKA2 large field-of-view millimeter continuum camera for the 30-m IRAM telescope

摘要

Millimeter-wave continuum astronomy is today an indispensable tool for bothgeneral Astrophysics studies and Cosmology. General purpose, largefield-of-view instruments are needed to map the sky at intermediate angularscales not accessible by the high-resolution interferometers and by the coarseangular resolution space-borne or ground-based surveys. These instruments haveto be installed at the focal plane of the largest single-dish telescopes. Inthis context, we have constructed and deployed a multi-thousands pixelsdual-band (150 and 260 GHz, respectively 2mm and 1.15mm wavelengths) camera toimage an instantaneous field-of-view of 6.5arc-min and configurable to map thelinear polarization at 260GHz. We are providing a detailed description of thisinstrument, named NIKA2 (New IRAM KID Arrays 2), in particular focusing on thecryogenics, the optics, the focal plane arrays based on Kinetic InductanceDetectors (KID) and the readout electronics. We are presenting the performancemeasured on the sky during the commissioning runs that took place betweenOctober 2015 and April 2017 at the 30-meter IRAM (Institut of Millimetric RadioAstronomy) telescope at Pico Veleta. NIKA2 has been successfully deployed andcommissioned, performing in-line with the ambitious expectations. Inparticular, NIKA2 exhibits FWHM angular resolutions of around 11 and 17.5arc-seconds at respectively 260 and 150GHz. The NEFD (Noise Equivalent FluxDensities) demonstrated on the maps are, at these two respective frequencies,33 and 8 mJy*sqrt(s). A first successful science verification run has beenachieved in April 2017. The instrument is currently offered to the astronomicalcommunity during the coming winter and will remain available for at least thenext ten years.