A wide field-of-view low-resolution spectrometer at APEX: Instrument design and scientific forecast

¹ Astronomy Instrumentation Group, University of Cardiff, The Parade CF24 3AA, UK
² Núcleo de Astronomía, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Av. Ejército 441, Santiago, Chile
³ Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, 38000 Grenoble, France
e-mail: monfardini@neel.cnrs.fr
⁴ Groupement d’Interet Scientifique KID, 38000 Grenoble and 38400 Saint Martin d’Hères, France
⁵ Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille), 13388 Marseille, France
e-mail: guilaine.lagache@lam.fr
⁶ Univ. Grenoble Alpes, CNRS, LPSC/IN2P3, 38000 Grenoble, France
⁷ European Southern Observatory, Karl Schwarzschild Straße 2, 85748 Garching, Germany
⁸ Univ. Grenoble Alpes, CNRS, IPAG, 38400 Saint Martin d’Hères, France
⁹ European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile
¹⁰ School of Earth and Space Exploration and Department of Physics, Arizona State University, Tempe, AZ 85287, USA

Received: 20 May 2020
Accepted: 24 July 2020

Abstract

Context. Characterising the large-scale structure in the Universe from present times to the high redshift epoch of reionisation is essential to constraining the cosmology, the history of star formation, and reionisation, to measuring the gas content of the Universe, and to obtaining a better understanding of the physical processes that drive galaxy formation and evolution. Using the integrated emission from unresolved galaxies or gas clouds, line intensity mapping (LIM) provides a new observational window to measure the larger properties of structures. This very promising technique motivates the community to plan for LIM experiments.

Aims. We describe the development of a large field-of-view instrument, named CONCERTO (for CarbON CII line in post-rEionisation and ReionisaTiOn epoch), operating in the range 130–310 GHz from the APEX 12-m telescope (5100 m above sea level). CONCERTO is a low-resolution spectrometer based on the lumped element kinetic inductance detectors (LEKID) technology. Spectra are obtained using a fast Fourier transform spectrometer (FTS), coupled to a dilution cryostat with a base temperature of 0.1 K. Two two kilo-pixel arrays of LEKID are mounted inside the cryostat that also contains the cold optics and the front-end electronics.

Methods. We present, in detail, the technological choices leading to the instrumental concept, together with the design and fabrication of the instrument and preliminary laboratory tests on the detectors. We also give our best estimates for CONCERTO sensitivity and give predictions for two of the main scientific goals of CONCERTO, that is, a [CII]-intensity mapping survey and observations of galaxy clusters.

Results. We provide a detailed description of the instrument design. Based on realistic comparisons with existing instruments developed by our group (NIKA, NIKA2, and KISS), and on the laboratory characterisation of our detectors, we provide an estimate for CONCERTO sensitivity on the sky. Finally, we describe, in detail, two of the main scientific goals offered by CONCERTO at APEX.