EMIR, the near-infrared camera and multi-object spectrograph for the GTC

EMIR at GTC

¹ Instituto de Astrofísica de Canarias, IAC, Vía Láctea s/n, 38205 La Laguna (S.C. Tenerife), Spain
e-mail: fgl@iac.es
² Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna (S.C. Tenerife), Spain
³ Isaac Newton Group of Telescopes, ING, 38700 La Palma (S.C. Tenerife), Spain
⁴ Departamento de Física de la Tierra y Astrofísica & Instituto de Física de Partículas y del Cosmos (IPARCOS), Universidad Complutense de Madrid, 38206 Madrid, Spain
⁵ Aix-Marseille Univ., CNRS, CNES, LAM, 13013 Marseille, France
⁶ Department of Astronomy, University of Florida, FL 32611, USA
⁷ European Southern Observatory, ESO, 85748 Garching bei München, Germany
⁸ Institut de Recherche en Astrophysique et Planétologie (IRAP), Université de Toulouse, CNRS, UPS, CNES, 14 Av. Edouard Belin, 31400 Toulouse, France
⁹ Institute of Astronomy, University of Cambridge, Madingley Rise, Cambridge CB3 0HA, UK
¹⁰ Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
¹¹ Departamento de Física Aplicada, Universidad de Alicante, San Vicente del Raspeig, 03690 Alicante, Spain
¹² School of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
¹³ Centro de Astronomía (CITEVA), Universidad de Antofagasta, Av. Angamos 601, Antofagasta 1271155, Chile

Received: 10 August 2022
Accepted: 9 September 2022

Abstract

We present EMIR, a powerful near-infrared (NIR) camera and multi-object spectrograph (MOS) installed at the Nasmyth focus of the 10.4 m GTC. EMIR was commissioned in mid-2016 and is offered as a common-user instrument. It provides spectral coverage of 0.9–2.5 µm over a field of view (FOV) of 6.67′ × 6.67′ in imaging mode, and 6.67′ × 4′ in spectroscopy. EMIR delivers up to 53 spectra of different objects thanks to a robotic configurable cold slit mask system that is located inside the cryogenic chamber, allowing rapid reconfiguration of the observing mask. The imaging mode is attained by moving all bars outside the FOV and then leaving an empty space in the GTC focal surface. The dispersing suite holds three large pseudo-grisms, formed by the combination of high-efficiency FuSi ion-etched ruled transmission grating sandwiched between two identical ZnSe prisms, plus one standard replicated grism. These dispersing units offer the spectral recording of an atmospheric window J, H, K in a single shot with resolving powers of 5000, 4250, 4000, respectively for a nominal slit width of 0.6″, plus the combined bands Y J or HK, also in a single shot, with resolution of ~1000. The original Hawaii2 FPA detector, which is prone to instabilities that add noise to the signal, is being replaced by a new Hawaii2RG detector array, and is currently being tested at the IAC. This paper presents the most salient features of the instrument, with emphasis on its observing capabilities and the functionality of the configurable slit unit. Sample early science data is also shown.