MIRADAS

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Latest News

November 2011
Subject: Kick-off for the MIRADAS instrument

Recently a contract was signed between GRANTECAN and the University of Florida on the design of a new instrument for the GTC. The instrument, MIRADAS, will be a multi-object near-IR spectrograph reaching a spectral resolution of 20000. It is conceived as a common-user instrument that will be located in the folded-Cassegrain focal station.

MIRADAS will be one of the third-generation instruments for the telescope and is led by Prof. Stephen Eikenberry from the University of Florida (USA), in collaboration with Universidad de Barcelona, Universidad Complutense de Madrid (UCM), Instituto de Astrofísica de Canarias (IAC), Institut de Física d'Altes Energies (IFAE), Institut d'Estudis Espacials de Catalunya (IEEC), and Instituto de Astronomía de la Universidad Nacional Autónoma de México (UNAM). The science team behind the instrument comprises a large number of scientists from 8 institutions within the GTC community.

The capability of MIRADAS to work at infrared wavelengths where obscuration by gas and dust between the stars is less of a problem, its multiplexing capability of observing several objects at the same time, and the high spectral resolution that can be reached make the instrument extremely attractive to tackle a wide range of scientific questions. All this, combined with the massive light-gathering power of the GTC provides us with a recipe to achieve very exciting scientific goals that will expand our knowledge in several key areas of astrophysics.

Examples of such key areas are the detailed study of massive stars in our galaxy that will help us understand galactic structure and the chemical history of our Milky Way. MIRADAS will also have an important impact for galaxies in our cosmic neighborhood, such as for instance in the study of massive black holes that lurk at the centers of many of these galaxies, and of the dynamical behavior of galaxies. The instrument also contemplates polarimetric measurements which open up a unique window in areas such as the study of cirmumstellar disks, planet formation, and even the possibility of mapping the surface structures of cool stars.

If all goes well for this very demanding instrument design, the science community could star to take profit from the capability of MIRADAS by 2017.

Overview of the MIRADAS conceptual design as it will be attached to the folded Cassegrain acquisition and guiding unit.

The MIRADAS focal plane layout with its up to 20 deployable pickup arms for separate objects.

Summary of Features

The basic MIRADAS concept is a near-infrared multi-object echelle spectrograph operating at spectral resolution R=20,000 over the 1-2.5µm bandpass. MIRADAS selects targets using ~20 deployable probe arms with pickoff mirror optics, each feeding a 4.0x1.2-arcsec field of view to the spectrograph. The spectrograph input optics also include a "slit slicer" which reformats each probe field into 3 end-to-end slices of a fixed 4.0x0.4-arcsec format – combining the advantages of minimal slit losses in any seeing conditions better than 1.2-arcsec, while at the same time providing some (limited) two!dimensional spatial resolution. The spectrograph optics then provide a range of configurations providing the observer with the ability to choose between maximal multiplex advantage and maximal wavelength coverage, with several intermediate options, depending upon the needs of the science program.

General Parameters

Parameter	Value	Comment
Target field of regard	5-arcminute diameter	Each probe arm patrols a "slice of pie" wedge of this circular field
Individual target field of view	4x1.2-arcsec
Slit slicer geometry	3 slices of 4.0x4.0-arcsec each
Detector focal plane	4096x2048 pixels	Mosaic of 2Kx2K HAWAII-2RG
Continuum sensitivity	J=18.0 mag H=17.7 mag K=16.7 mag	S/N=10 for 1-hour on-source exposure
Emission line sensitivity	5x10-18 ergs/cm2/s (point) 8x10-18 ergs/cm2/s (resolved)	S/N=10 for 1-hour on-source exposure; resolved source assumes 1 square arcsecond detect cell

Multiplex Configurations

Configuration	MXS Targets	Instantaneous Bandpass
SO-mode short	1	1.02-1.79 µm
SO-mode long	1	1.27-2.50 µm
Medium MXS J	5	1.14-1.32 µm
Medium MXS H	5	1.50-1.82 µm
Medium MXS K	5	1.92-2.49 µm
Maximum MXS	20	Any SINGLE order from Table 3

MIRADAS Echelle Orders

Order	Wavelength (µm)	Band	Order	Wavelength (µm)	Band
14	2.322-2.495	K	24	1.373-1.432	-
15	2.172-2.322	K	25	1.319-1.373	-
16	2.040-2.172	K	26	1.270-1.319	J
17	1.923-2.040	K	27	1.223-1.270	J
18	1.819-1.923	-	28	1.180-1.223	J
19	1.726-1.819	H	29	1.140-1.180	J
20	1.642-1.726	H	30	1.103-1.140	-
21	1.565-1.642	H	31	1.068-1.103	J-Io
22	1.495-1.565	H	32	1.035-1.068	J-Io
23	1.432-1.495	-	33	1.004-1.035	J-Io

Note that additional combinations of multiplex and wavelength coverage are also possible. By selecting different order!sorting filters and probe output masks, the observer could choose any combination of target multiplex (N_MXS) and wavelength coverage by consecutive orders (N_order), as long as the product N_MXS * N_order < 20. For instance, a configuration with 10 MXS targets and a wavelength coverage from 2.040 to 3.322 microns (orders 15 and 16) would work.

Support Astronomer in charge of MIRADAS in GTC

• (Contact person)

More Information:

• URL: http://www.astro.ufl.edu/~raines/snr-miradas.html

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