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

Abstract

Context. Millimetre-wave continuum astronomy is today an indispensable tool for both general astrophysics studies (e.g. star formation, nearby galaxies) and cosmology (e.g. cosmic microwave background and high-redshift galaxies). General purpose, large-fieldof-view instruments are needed to map the sky at intermediate angular scales not accessible by the high-resolution interferometers (e.g. ALMA in Chile, NOEMA in the French Alps) and by the coarse angular resolution space-borne or ground-based surveys (e.g. Planck, ACT, SPT). These instruments have to be installed at the focal plane of the largest single-dish telescopes, which are placed at high altitude on selected dry observing sites. In this context, we have constructed and deployed a three-thousand-pixel dual-band (150 GHz and 260 GHz, respectively 2 mm and 1.15 mm wavelengths) camera to image an instantaneous circular field-of-view of 6.5 arcmin in diameter, and configurable to map the linear polarisation at 260 GHz. Aims. First, we are providing a detailed description of this instrument, named NIKA2 (New IRAM KID Arrays 2), in particular focussing on the cryogenics, optics, focal plane arrays based on Kinetic Inductance Detectors, and the readout electronics. The focal planes and part of the optics are cooled down to the nominal 150 mK operating temperature by means of an adhoc dilution refrigerator. Secondly, we are presenting the performance measured on the sky during the commissioning runs that took place between October 2015 and April 2017 at the 30-m IRAM telescope at Pico Veleta, near Granada (Spain). Methods. We have targeted a number of astronomical sources. Starting from beam-maps on primary and secondary calibrators we have then gone to extended sources and faint objects. Both internal (electronic) and on-the-sky calibrations are applied. The general methods are described in the present paper. Results. NIKA2 has been successfully deployed and commissioned, performing in-line with expectations. In particular, NIKA2 exhibits full width at half maximum angular resolutions of around 11 and 17.5 arcsec at respectively 260 and 150 GHz. The noise equivalent flux densities are, at these two respective frequencies, 33 ± 2 and 8 ± 1 mJy s 1/2 . A first successful science verification run was achieved in April 2017. The instrument is currently offered to the astronomy community and will remain available for at least the following ten years.Key words. instrumentation: detectors -instrumentation: photometers -instrumentation: polarimeters -submillimeter: ISMsubmillimeter: galaxies -cosmic background radiation Article published by EDP Sciences A115, page 1 of 15 A&A 609, A115 (2018)

KISS: a spectrometric imager for millimetre cosmology

“…The efforts on many incoming SZ experiments are oriented on reaching angular resolution down to 20" to realise detailed clusters maps. This goal is reached by exploiting high resolution millimetre telescopes with new generation instrumentations, like with NIKA [7], NIKA2 [8] and MUSTANG-2 [9], reached by exploiting high resolution millimetre telescopes with new generation instrumentations.…”

The KISS Experiment

“…The former can be addressed with continuum dualband observations at high angular resolution such as those performed e.g. with NIKA [3] and NIKA2 [4]. For the latter, multi-wavelength observations are needed to separate the different components and to add complementary information.…”

“…Compared to the predecessors that are imagers (e.g. ACT [5], Mustang [6], SPT [7], Bolocam [8], the satellite Planck [9], NIKA [3] and NIKA2 [4]), KISS is a Fourier Transform Spectrometer (FTS) and allows for accurate component separation for low redshift clusters.…”

In-Flight Performance of the LEKIDs of the OLIMPO Experiment

“…In the microwaves, KID technology has been already proven for ground-based experiments by NIKA [4] and NIKA2 [5]. OLIMPO [6] has qualified the KID technology in a representative near-space environment, relevant for TRL (Technology Readiness Level) advancement in view of future space missions [1,7,8,9,10,11,12,13,14,15].…”