© 2

01

3: In

stitu

to d

e A

stro

no

mía

, U

NA

M -

Fo

urt

h S

cie

nc

e M

ee

tin

g w

ith

th

e G

TCEd

. C

. M

uñ

oz-

Tuñ

ón

& J

. M

. R

od

ríg

ue

z-Es

pin

osa

RevMexAA (Serie de Conferencias), 42, 93–95 (2013)

MIRADAS - THE NEXT-GENERATION NEAR-INFRARED

SPECTROGRAPH FOR THE GTC

S. S. Eikenberry1 and The MIRADAS Instrument Consortium2,3,4,5,6,7,8

RESUMEN

Se describe el instrumento MIRADAS (“Mid-resolution InfRAreD Astronomical Spectrograph”) que esta siendodesarrollado por el consorcio MIRADAS (Universidad de Florida, Universidad de Barcelona, Universidad deComplutense de Madrid, Instituto de Astrofısica de Canarias, Institut de Fısica d’ Altes Energies, Institutd’ Estudis Espacials de Catalunya y la Universidad Nacional Autonoma de Mexico) para el Gran TelescopioCanarias. MIRADAS es el instrumento astronomico mas potente de su clase hasta ahora. La combinacion dela superficie colectora del GTC con la capacidad de espectroscopıa multi-objeto con resolucion intermedia enel infrarrojo cercano y la excelente eficiencia observacional de MIRADAS, mas de un orden de magnitud mejorque los instrumentos disponibles hoy dıa, resulta sin parangon para llevar a cabo algunos de los desafıos masimportantes de las proximas decadas. En lo que sigue repasamos los motores cientıficos del instrumento, sudiseno basico, y su estado actual de desarrollo.

ABSTRACT

We describe the Mid-resolution InfRAreD Astronomical Spectrograph (MIRADAS) being developed by theMIRADAS Consortium institutions (including the University of Florida, Universidad de Barcelona, UniversidadComplutense de Madrid, Instituto Astrofısica de Canarias, Institut de Fısica d’ Altes Energies, Institut d’Estudis Espacials de Catalunya and Universidad Nacional Autonoma de Mexico) for the Gran TelescopioCanarias. MIRADAS is the most powerful astronomical instrument of its kind ever envisioned. The combinationof the collecting area of GTC and the multi-object mid-resolution near-infrared spectra provided by MIRADASmake its capabilities unparalleled for addressing some of the leading scientific challenges of the coming decades,with an observing efficiency more than an order of magnitude greater than current capabilities for 10-meter-class telescopes. We briefly review the science drivers for the instrument, the basic design features, and thecurrent status of the instrument development.

Key Words: instrumentation: spectrographs — telescopes

1. INTRODUCTION

MIRADAS is the most powerful astronomical in-strument of its kind ever envisioned. The combina-tion of the collecting area of GTC and the multi-object mid-resolution near-infrared spectra providedby MIRADAS make its capabilities unparalleled foraddressing some of the leading scientific challengesof the coming decades, with an observing efficiencymore than an order of magnitude greater than cur-rent capabilities for 10-meter-class telescopes.

The MIRADAS science team –comprised of39 scientists from 8 institutions within the GTC

1Department of Astronomy, University of Florida,Gainesville, FL 32611, USA (eikenberry@astro.ufl.edu).

2University of Florida, Gainesville, FL, USA 32611, USA.3Universidad de Barcelona, Spain.4Universidad Complutense de Madrid, Spain.5Institut de Fsica d’Altes Energies, Spain.6Institut d’Estudis Espacials de Catalunya, Spain.7Instituto Astrofisica de Canarias, Spain.8Universidad Nacional Autonoma de Mexico, Mexico.

community– has identified four key science casesfor MIRADAS which form the Design Reference

Cases for MIRADAS – the scientific performancecapabilities which provide the fundamental require-ments drivers for the instrument. In addition tothe Design Reference Cases, the MIRADAS ScienceTeam have also identified more than 10 additionalscience cases which will make excellent scientific useof the MIRADAS capabilities determined by the De-sign Reference Case drivers, ranging from stellarmagnetic fields to ‘Galactic archeology’ of the Milkyto compact objects and relativistic astrophysics tointermediate-redshift galaxies.

Using these science cases as our guide, our studypresents a powerful, robust instrument concept forMIRADAS, from optical to mechanical, electrical,software, and systems designs. We have thoroughlyinvestigated this design concept and guided it by alarge number of trade studies to provide optimal so-lutions for the MIRADAS science requirements. Our

93

© 2

01

3: In

stitu

to d

e A

stro

no

mía

, U

NA

M -

Fo

urt

h S

cie

nc

e M

ee

tin

g w

ith

th

e G

TCEd

. C

. M

uñ

oz-

Tuñ

ón

& J

. M

. R

od

ríg

ue

z-Es

pin

osa

94 EIKENBERRY

‘Minimal R & D’ approach results in the overwhelm-ing majority of this powerful design concept beingbased on proven technologies and systems. Many ofthese, from cryogenic mechanisms to image-slicingintegral field units to instrument control software todata reduction pipelines, are cloned from or closelybased on previous instruments successfully built andused at MIRADAS consortium institutions. Thus,we believe we have developed an approach to MI-RADAS which minimizes technical risk while pro-viding maximal scientific performance.

2. MIRADAS SCIENCE CASES

The science case for MIRADAS is the drivingforce behind the instrument – ultimately, the successof astronomical instruments is defined by the sciencethey produce. Thus, the fundamental approach todefining the instrument and guiding the design pro-cess must be science-driven. The MIRADAS ScienceWorking Group has identified four key science casesfor MIRADAS. These key cases form the ‘DesignReference Cases’ for MIRADAS – the scientific per-formance capabilities which provide the fundamentalrequirements drivers for the instrument. These sci-ence cases effectively define what MIRADAS mustdo scientifically speaking. These key cases include:

• Massive Stars in the Milky Way - Thestudy of massive stars is one of the key areas inmodern astrophysics. High-mass stars are the domi-nant luminosity source in spiral galaxies like our ownMilky Way Way and in far away starbursts, regionsof intense star formation. They are the primary en-gines of abundance evolution in the Universe, andare the primary source of turbulent energy and starformation feedback to the interstellar medium – allkey contributors to the mysteries of galaxy evolutionacross cosmic time. In addition, these stars are theprogenitors of compact objects (neutron stars andblack holes) and the source of super-luminous explo-sions such as gamma-ray bursts and hypernovae, thestudy of which have become important subfields intheir own right. Despite this importance, we cur-rently understand very little about these stars andtheir evolutionary life cycles and deaths. MIRADASwill allow the first major survey of the majority ofthese previously-hidden objects in the Milky Wayand nearby galaxies.

• Chemo-Dynamical Surveys of the Inner

Galaxy deliver transformational breakthroughs inour understanding of the formation and evolutionof the Milky Way. Knowledge of the abundancepatterns in all the major components of the innerGalaxy will allow us to make inferences about its

history. To accomplish this, abundances need to bemeasured at a variety of locations. Furthermore, thelink between dynamics, star formation, and chemi-cal history is poorly understood. Thus investigationsusing a number of elemental tracers are needed toexplore the limitations for the observations and pro-vide the exact number densities of stars. MIRADASwill provide 20x the observational power previouslyavailable for such work, and thus revolutionize thisfield.

• Building Blocks of Galaxy Evolution at

Intermediate Redshift - One of the most activefields in modern astrophysics is the study of the for-mation and evolution of galaxies. To understandhow and when the galaxies built up their stellar massand acquired their morphology are among the mostimportant issues of observational cosmology. BlueCompact Dwarfs galaxies (BCDs) are those dwarfswith low luminosity, strong emission lines super-posed on a blue continuum, and compact optical size.BCDs undergo an intense burst of star formation,which makes them extremely interesting for study-ing how this process works and the physical condi-tions under which it can be triggered, maintainedor quenched. MIRADAS working on GTC will al-low the kinematical analysis of numerous samples ofBCDs at intermediate redshift, crucial for better un-derstanding of the main processes involved in galaxyassembly and evolution.

• Infrared Spectro-Polarimetry - New

Windows on Stellar Astrophysics - Astrophysi-cal plasmas and magnetic fields are inextricably cou-pled to each other. But magnetic fields are elu-sive; they cannot be detected directly with stan-dard observational techniques. However, magneticfields DO produce many signatures which are evi-dent in the POLARIZATION of light. Thus, po-larization, the third fundamental property of light,encodes all the quantitative information on the mag-netic fields where it originated and on the symme-tries of the environment of the emitting atoms, ions,or molecules. The light coming from most naturalsources is only weakly polarized and the polarizationsignals are difficult to detect. Thus, studying theseeffects in stars other than the Sun requires spectro-polarimetry from 10-meter class telescopes such asthe GTC. The observation of polarized near-infraredspectra using MIRADAS will allow a completely newwindow on stellar magnetism.

They then lead to a ‘flowdown’ to MIRADAS sci-entific requirements which in turn lead to top-levelfunctional design requirements, and these in turnguide and constrain the detailed design.

© 2

01

3: In

stitu

to d

e A

stro

no

mía

, U

NA

M -

Fo

urt

h S

cie

nc

e M

ee

tin

g w

ith

th

e G

TCEd

. C

. M

uñ

oz-

Tuñ

ón

& J

. M

. R

od

ríg

ue

z-Es

pin

osa

MIRADAS - GTC 95

Fig. 1. Spectral grasp versus multiplex advantage for

MIRADAS and other competing spectrographs on 8 m

to 10 m telescopes.

We also have developed many other sciencecases which are enabled by the same design of MI-RADAS, demonstrating the flexibility and power ofMIRADAS, and its potential for use by the broadscientific community participating in the Gran Tele-scopio Canarias.

3. MIRADAS INSTRUMENT FEATURES

The basic MIRADAS concept is a near-infraredmulti-object echelle spectrograph operating at spec-

tral resolution R=20000 over the 1–2.5 µm band-pass. MIRADAS selects targets using ∼20 deploy-able probe arms with pickoff mirror optics, each feed-ing a 4.0 × 1.2 arcsec field of view to the spectro-graph. The spectrograph input optics also include aslit slicer which reformats each probe field into 3 end-to-end slices of a fixed 4.0×0.4 arcsec format – com-bining the advantages of minimal slit losses in anyseeing conditions better than 1.2-arcsec, while at thesame time providing some (limited)two-dimensionalspatial resolution. The spectrograph optics then pro-vide a range of configurations providing the observerwith the ability to choose between maximal multi-plex advantage and maximal wavelength coverage,with several intermediate options, depending uponthe needs of the science program.

As we can see in Figure 1, MIRADAS providesgreater spectral grasp per target for a multiplex fac-tor of N = 5 than other competing spectrographswhich only observe a single target.

4. MIRADAS STATUS

The initial contract for Preliminary Design Phasewas signed in July 2011. We have a low-risk minimalR & D design. We expect documents delivered forPDR by end of October 2012, with PDR in mid/lateNovember 2012. Assuming prompt award of finaldesign/construction contract, we expect to be com-missioning MIRADAS in 2016.