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

Adam, R., Adane, A., Ade, Peter, André, P., Andrianasolo, A., Aussel, H., Beelen, A., Benoit, A., Bideaud, A., Billot, N., Bourrion, O., Bracco, A., Calvo, M., Catalano, A., Coiffard, G., Comis, B., De Petris, M., Désert, F.X., Doyle, S., Driessen, E.F.C., Pisano, Giampaolo, Rigby, Andrew and Tucker, Carole 2018. The NIKA2 large field-of-view millimeter continuum camera for the 30-m IRAM telescope. Astronomy and Astrophysics 609 , A115. 10.1051/0004-6361/201731503

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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. CMB - cosmic microwave background and high-redshift galaxies). General purpose, large-field-of-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-ofview of 6.5 arcminutes 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 (KID), 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 ad-hoc 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-meter IRAM (Institut of Millimetric Radio Astronomy) 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 (FWHM) angular resolutions of around 11 and 17.5 arc-seconds at respectively 260 and 150 GHz. The noise equivalent flux densities (NEFD) 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.

Item Type: Article
Date Type: Published Online
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Publisher: EDP Sciences
ISSN: 0004-6361
Date of First Compliant Deposit: 7 December 2017
Date of Acceptance: 13 September 2017
Last Modified: 05 Jun 2018 14:45

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