MATISSE, the VLTI mid-infrared imaging spectro-interferometer

¹ Laboratoire Lagrange, Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Boulevard de l’Observatoire, CS 34229, 06304 Nice Cedex 4, France
e-mail: bruno.lopez@oca.eu
² Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
³ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁴ NOVA Optical IR Instrumentation Group at ASTRON, The Netherlands
⁵ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
⁶ European Southern Observatory Headquarters, Karl-Schwarzschild-Straße 2, 85748 Garching bei München, Germany
⁷ European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile
⁸ Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Eötvös Loránd Research Network (ELKH), Konkoly-Thege Miklós út 15-17, 1121 Budapest, Hungary
⁹ Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
¹⁰ NASA Goddard Space Flight Center Astrophysics Science Division, Code 660, Greenbelt, MD 20771, USA
¹¹ Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1090 GE Amsterdam, The Netherlands
¹² MPE Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse, 85741 Garching, Germany
¹³ Departamento de Astronomía, Universidad de Concepción, Casilla 160-C, Concepción, Chile
¹⁴ Nicolaus Copernicus Astronomical Centre, Polish Academy of Sciences, Bartycka 18, 00-716 Warszawa, Poland
¹⁵ Unidad Mixta Internacional Franco-Chilena de Astronomía (CNRS UMI 3386), Departamento de Astronomía, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile
¹⁶ Department of Astrophysics, University of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria
¹⁷ I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
¹⁸ LESIA – Laboratoire d’études spatiales et d’instrumentation en astrophysique, Observatoire de Paris, 5 place Jules Janssen, 92190 Meudon, France
¹⁹ GEOAZUR, Campus CNRS, 1 Sophia Antipolis, 06560 Valbonne, France
²⁰ Zselic Park of Stars, 064/2 hrsz., 7477 Zselickisfalud, Hungary
²¹ AIM, CEA, CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris Cité, 91191 Gif-sur-Yvette, France
²² National Astronomical Research Institute of Thailand, 191 Siriphanich Bldg., Huay Kaew Rd., Suthep, Muang Chiang Mai 50200, Thailand
²³ Sydney Institute for Astronomy, School of Physics, A28, The University of Sydney, NSW 2006, Australia
²⁴ Institute for Mathematics, Astrophysics and Particle Physics, Radboud University, PO Box 9010 MC 62, 6500 GL Nijmegen, The Netherlands
²⁵ SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
²⁶ Institute of Theoretical Physics and Astrophysics University of Kiel, 24118 Kiel, Germany

Received: 8 July 2021
Accepted: 9 December 2021

Abstract

Context. Optical interferometry is at a key development stage. The Very Large Telescope Interferometer (VLTI) has established a stable, robust infrastructure for long-baseline interferometry that is usable by general astronomical observers. The present second-generation instruments offer a wide wavelength coverage and improved performance. Their sensitivity and measurement accuracy lead to data and images of high reliability.

Aims. We have developed the Multi AperTure mid-Infrared SpectroScopic Experiment (MATISSE) to access, for the first time, high resolution imaging in a wide spectral domain. Many front-line topics are explored with this new equipment, including: stellar activity and mass loss; planet formation and evolution in the gas and dust disks around young stars; and environment interaction and accretion processes around super massive black holes in active galactic nuclei.

Methods. The instrument is a spectro-interferometric imager in the transmission windows called L, M, and N, from 2.8 to 13.0 microns, combining four optical beams from the VLTI’s unit or auxiliary telescopes. Its concept, related observing procedure, data reduction, and calibration approach, is the product of 30 years of instrumental research and has benefitted from the expertise developed in the frame of the VLTI’s first generation instruments. The instrument utilises a multi-axial beam combination that delivers spectrally dispersed fringes. The signal provides the following quantities at several spectral resolutions: photometric flux, coherent fluxes, visibilities, closure phases, wavelength differential visibilities and phases, and aperture-synthesis imaging.

Results. This article provides an overview of the physical principle of the instrument and its functionalities. The motivation of the choice of the instrumental concept and the characteristics of the delivered signal are detailed with a description of the observing modes and of their performance limit. MATISSE offers four spectral resolutions in L&M bands, namely 30, 500, 1000 and 3400, and 30 and 220 in the N band, and it provides an angular resolution down to 3 mas for the shortest wavelengths. The MATISSE stand-alone sensitivity limits are 60 mJy in L and 300 mJy in N. The paper gives details of the sensitivity limits for the different measurables and their related precision criteria, considering telescope configurations and spectral resolutions. We also discuss the gain provided with the GRA4MAT fringe tracker. An ensemble of data and reconstructed images illustrate the first acquired key observations.

Conclusions. The instrument has been in operation at Cerro Paranal, ESO, Chile, since 2018, and has been open for science use by the international community since April 2019. The first scientific results are being published now.