Gran Telescopio CANARIAS

Observatorio del Roque de los Muchachos
La Palma

• Instrument Overview
• Summary of Features
• Scientific Cases
• Observing Modes
• Imaging Mode
• Spectroscopy Mode
• FRIDA and GTCAO
• FRIDA contact persons at GTC
• More Information

Instrument Overview

FRIDA (inFRared Imager and Dissector for Adaptive optics) is an Integral Field Spectrograph (IFS) working in the near-infrared wavelength ranges with imaging capability. It will make use of the GTC Adaptive Optics system (GTCAO) at the Nasmyth-B focal station.

The instrument will deliver imaging and 3D spectroscopy at the diffraction limit of the GTC (46 mas in the K-band) with adequate Nyquist sampling. It will have a integral-field camera based on a comprehensive image dissector system using mirrors, several cameras to capture different spatial scales, a variety of filters and 3 diffraction gratings optimized for different resolutions and spectral bands. Spectral resolutions will go up to 30000.

FRIDA will use a 2048 by 2048 pixels infrared detector HAWAII-2RG with a control system that is being developed by the project team at the IAC for the instrument EMIR.

It is a project led by the Instituto de Astronomía de la Universidad Nacional Autónoma de México (UNAM) in partnership with the Instituto de Astrofísica de Canarias (IAC), the University of Florida (UF), and the Universidad Complutense de Madrid (UCM).

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Summary of Features

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Scientific Cases

FRIDA unique design provides the ability to generate images of great spatial resolution, of the order of some tens of milliseconds of arc. This, together with its Integral Field Spectroscopy (IFS) capabilities, open up the possibilities of study of our Universe.

• The study of the planetary nebulae and planetary pre-nebulae nuclei. These objects represent the last stages of life of the stars between 1 and 8 solar masses. These stars are the most common in galaxies and therefore determinants in their evolution. In the last two decades, and thanks to the high spatial resolution data generated by the HST, as well as very high resolution spectra, it has been found that the development of a large number of planetary nebulae is dominated by multipolar structures with point and mirror symmetry, high-speed collimated jets and equatorial toroids of granular structure composed of multiple cometary nodes of low degree of ionization. The origin of these structures is not clear and their existence in these late stages of stellar evolution remains surprising. In recent times, field research indicates that, most likely, the pathways of origin of these phenomena are the presence of magnetic fields and binary systems, including planets in their nuclei.
• The study of moons, craters and volcanoes of the planets of our Solar System.
• FRIDA will be able to solve for the near cases, either by direct image or by IFS, the structure of the stellar nucleus. Nucleus kinematic data at scales of only some astronomical units could be obtained, revealing the areas of origin of the collimated jets and, consequently, allowing to distinguish between the various theories of jets generation or collimated high-speed flows. Gemini North observations with NIFS supported by the ALTAIR AO system of the young and complex planetary nebula Hb 12 reached 0.1 arcsec spatial resolution, revealing a multitude of previously unknown structures, bringing us closer to understanding the physical mechanisms of formation and evolution of these types of objects. FRIDA observations for this object, as a comparison, will reach 5 times better spatial resolution (0.020 arcsec) and a spectral resolution of 10 km/s. These data will undoubtedly strip the morphological and dynamic structure of the early stages of formation of bipolar planetary nebulae such as Hb 12.
• Since FRIDA will operate in the infrared range 0.9-2.5 um as well, it will be possible to distinguish and study in detail the dust and cold (neutral) material inside and near the areas of ionized material. It will be possible to trace and analyze the photo-dissociation transition of the radiation field over the partially ionized material. On the other hand, the chemical composition and physical parameters such as electron density and temperature, at millisecond arc scales, of the ionized material and the transition zones, can be analyzed by means of low and intermediate resolution spectroscopy in the infrared bands that comprise the design FRIDA. This will provide fundamental elements to solve the important problem of abundance discrepancy or ADF (abundance discrepancy factor) that results from deriving ionic abundances from collision lines and recombination lines, both in planetary nebulae and in H II regions.
• It will be possible to distinguish binary companions close to each other, planetary formation discs around young stars, measure the speed of gas with accuracies that cannot yet be achieved with existing instruments, and study galaxies with peculiar and intense star formation (Starbursts), the interactions between galaxies and the properties and evolution of the clusters of galaxies that populate the Universe.

FRIDA will implement a stellar Coronography Mode. Two occulting masks will be installed in the field-mask wheel with radii of about 4λ/D in H (130 mas) and K (180 mas). Corresponding Lyot stops will be installed in the pupil-mask wheel. Will be used for both imaging and spectroscopy. Raw contrasts estimation is of 10e-4 to 10e-5.

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Observing Modes

Imaging Mode

As FRIDA will have a HAWAII-2RG detector for the two modes of operation, the instrument has a configuration such that once the corrected beam from the AO system enters, one of the three available scales can be chosen and then passes through the collimator-chamber system before being diverted to the detector. It will be possible to use broadband and narrow filters, in three different scales:

• Fine scale. 10 milliseconds of arc per pixel, providing adequate sampling to the first Airy ring, limited by diffraction in the z and J bands. Currently, no other instrument in operation in large telescopes can provide this scale.
• Medium scale. 20 milliseconds of arc per pixel, allowing adequate sampling in the H and K bands, where the AO system is expected to reach its maximum correction.
• Coarse scale. 40 milliseconds of arc per pixel, designed primarily for acquisition purposes in IFS mode.

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Integral Field Spectroscopy Mode

FRIDA's Integral Field Spectroscopy mode will allow 3D spectroscopy using an Integral monolithic Field Unit, with spectral resolution powers:

• Low R = 1000 (HK) to 1400 (ZJ)
• Intermediate R = 4000 (Z, J, H, K)
• High R = 25000 (0.04 um window in H) to 32000 (0.07 um window in K)

FRIDA will be able to segment the images into 30 sections while preserving both the spatial and spectral information of each one of them, so that by combining high spectral resolution and high spatial resolution it makes it a unique instrument in its class.

In this mode, the instrument acquires a configuration in which the optical beam, after passing through the camera that defines the scale, will continue to the IFU and double-pass spectrograph, to the desired diffraction grating and, finally, get to the detector. Different gratings available and their main characteristics are summarized in the Table below:

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FRIDA and GTCAO

FRIDA will be installed at the Nasmyth-B platform behind the output focus of the GTC Adaptive Optic system. GTCAO  will routinely deliver subarcsec resolutions down to the GTC diffraction limit, this being about 4 times that provided by HST at the same IR wavelengths. FRIDA is designed to fully exploit these resolutions in its two observation modes: direct imaging and IFSy, both working in the 0.9-2.5 um range. Two unique capabilities of FRIDA with respect to current or planned 2D spectrographs are:

• 1) its high spectral resolution mode of R = 30,000;
• 2) its separate imaging mode which will allow the observer very fast switch to the IFS mode. The combination will allow the user a fast selection of the field of interest for follow up spectroscopy, and facilitate a fast acquisition in the small FoV of the integral field unit.

GTCAO is a Shack-Hartmann-based wave-front sensor working with NGS at optical wavelengths. For a median seeing of 0.65 arcsec at the GTC site, it is expected to provide  an on-axis Strehl ratio of ~0.60 in K-band, with guide stars of m(R) = 6-12,  down to ~0.30 for m(R)=15. Measurements  of the isoplanatic angle at the ORM indicate a degradation of the Strehl in K-band to 10% when the NGS is at 30 arcsec from the science target. The future implementation of a Laser Guide Star in GTCAO improve all of the above performances.

FRIDA Nyquist sample the diffraction limit of GTC in  J-, H- and K-bands in its imaging mode, in K-band  in its integral field mode, and partially in H- and J-bands in the integral field mode.

FRIDA’s ultimate performance is foreseen in the K-band where GTCAO is also expected to achieve  maximum atmosphere correction. In this case, FRIDA will deliver images and spectra with spatial resolutions close to GTC diffraction limit at 2 um, FWHM ~44 mas, with maximized image  contrast  and high throughput for point-like sources.

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FRIDA contact persons at GTC

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More Information:

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Last modified: 24 October 2022