GMACS: The Wide-Field, Multi-Object Spectrograph for the Giant Magellan Telescope Jennifer Marshall Texas A&M University
http://kicp-workshops.uchicago.edu/decam-nfc2018/
First Generation Instruments Instrument / Mode Capabilities λ Range, μm Resolution Field of View G-CLEF / NS, GLAO Optical High Resolution Spectrograph / PRV 0.35 0.95 20 100K 7 x 0.7,1.2 fibers GMACS / NS, GLAO Wide-Field Optical Multi- Object Spectrograph 0.36 1.0 1,500 4,000 (10K w/ MANIFEST) 40-60 arcmin 2 GMTIFS / LTAO, NGSAO NIR AO-fed IFS / Imager 0.9 2.5 5,000 & 10,000 10 / 400 arcsec 2 GMTNIRS / NGSAO, LTAO JHKLM AO-fed High Resolution Spectrograph 1.2 5.0 50K, 100K 1.2 long-slit MANIFEST* / NS, GLAO Facility Robotic Fiber Feed 0.36 1.0 20 diameter
International GMACS team D.L. DePoy, J. L. Marshall, Casey Papovich, Travis Prochaska, Luke Schmidt, Erika Cook (Texas A&M) Cynthia Froning (UT-Austin) Soojong Pak, Tae-Geun Ji, Hye-In Lee, (Kyung Hee University, Korea) Claudia Mendes de Oliveira, Rafael Ribeiro, Daniel Faes, Aline Souza, Mario Almeida (Sao Paolo, Brazil) Damien Jones (Australia) Keith Taylor (California) With contributions from Steve Shectman, Carnegie Observatories GMACS Science Forum GMT SAC GMT staff MANIFEST Team, Australia Matthew Colless Jon Lawrence Many others (Paul Scowen, ASU)
GMACS science goals General use spectrograph Performance optimized for faint targets Exploits GMT s large collecting area and wide field Follow up objects identified by DES/LSST GMACS will be able to take a spectrum of any object imaged by LSST Goal: spectrum of any LSST alert within ~1 hour
GMACS Science Drivers Science Case constraints Time-domain science Brown dwarf/exoplanet atmospheres (weather) Star/Star Cluster ages YSO accretion rates Dwarf Galaxy dynamics Stellar Abundances Redshift surveys (LSST, DES follow-up) Galaxy assembly, IGM/CGM studies Properties of Galaxies during Reionization High rel. precision/repeatability/efficiency; large simultaneous wavelength coverage 5 FOV, blueward of JWST wavelength coverage. High stability for transit spectroscopy. <2 Å resolution at Li 6708Å for age measurements; blue coverage (Ca HK) simultaneous coverage of Balmer lines/break (365-656 nm) Coverage of CaT (850 nm, R~5000); 3 km/s velocity precision, high stability. 20 FOV preferable R~5000, blue/red wavelength coverage (370-540 nm; CaT 850 nm) High multiplexing, slitlength requirement: source density will be ~50-60 arcmin -2. FOV as large as possible. Large simultaneous wavelength coverage to improve efficiency. R~3000 and redder wavelength coverage for absorption line studies of z > 1 galaxies. Very red coverage (>900 nm for Ly-α at z > 6.5), higher resolution and high multiplexing/fov helpful (~0.5-1 source/arcmin 2 )
Technical requirements High throughput across wide wavelength range Maintain compatibility with MANIFEST fiber positioner
GMACS design concept Weight: 5500 kg (12100 lb) 5.23m (17.2ft) 2.73m (9.0ft) 2.73m (9.0ft)
Design choices Weight: 5500 kg (12100 lb) Gregorian slit mask-fed Maximum throughput Refractive optics Maximum throughput No folds of convenience Maximum throughput Large instrument Two channels Maximum throughput Simultaneous wavelength coverage in low resolution mode VPH gratings Maximum throughput Adjustable cameracollimator angle 2.73m (9.0ft) 2.73m (9.0ft) 5.23m (17.2ft)
Optical design Transmissive design Panchromatic collimator Beam ~270mm 7.4 diameter field of view Dichroic to split beam Blue- and red-optimized cameras Articulated arms for VPH grating use Detector format: 8k x 12k, 15μm pixels Image quality linked to MANIFEST integration Goal: 80% EE at 0.15 arcsec Blue camera+panchromatic collimator Blue camera optical design
Optomechanical design Structural elements Interface to telescope Flexure compensation Numerous ~300mm class lenses Lens barrels and cells design Mechanisms Slit mask interchange Camera/collimator angle articulation Grating/filter selector Shutter Flexure compensation 450mm Collimator Dichroic Grating & Filter Red Camera CaF 2 FPL5 1 1378mm PSK 3 Silica Shutt er Grating & Filter Blue Camera PSK 3 PSK 3 FPL5 1 CaF 2 Silica 2 x 3 Array of 4k 2 CCDs LN 2 Dewar
MANIFEST coordination Ultimately GMACS will be used with MANIFEST fiber feed Allows multi-object observations over full corrected 20 arcminute diameter field (~300 arcmin 2 field) Re-mapping of slit to allow higher resolution GMACS resolution up to R~15000 Higher resolution means more objects fit in focal plane Better ability to observe transients in real time with repositionable fibers MANIFEST fibers positioned with Starbugs:
GMACS design Many more details in 2016 (and soon 2018) SPIE papers: instrumentation.tamu.edu
GMACS Science Drivers Science Case constraints Time-domain science Brown dwarf/exoplanet atmospheres (weather) Star/Star Cluster ages YSO accretion rates Dwarf Galaxy dynamics Stellar Abundances Redshift surveys (LSST, DES follow-up) Galaxy assembly, IGM/CGM studies Properties of Galaxies during Reionization High rel. precision/repeatability/efficiency; large simultaneous wavelength coverage 5 FOV, blueward of JWST wavelength coverage. High stability for transit spectroscopy. <2 Å resolution at Li 6708Å for age measurements; blue coverage (Ca HK) simultaneous coverage of Balmer lines/break (365-656 nm) Coverage of CaT (850 nm, R~5000); 3 km/s velocity precision, high stability. 20 FOV preferable R~5000, blue/red wavelength coverage (370-540 nm; CaT 850 nm) High multiplexing, slitlength requirement: source density will be ~50-60 arcmin -2. FOV as large as possible. Large simultaneous wavelength coverage to improve efficiency. R~3000 and redder wavelength coverage for absorption line studies of z > 1 galaxies. Very red coverage (>900 nm for Ly-α at z > 6.5), higher resolution and high multiplexing/fov helpful (~0.5-1 source/arcmin 2 )
GMACS Science Drivers Science Case Time-domain science Brown dwarf/exoplanet atmospheres (weather) Star/Star Cluster ages YSO accretion rates constraints High rel. precision/repeatability/efficiency; large simultaneous wavelength coverage 5 FOV, blueward of JWST wavelength coverage. High stability for transit spectroscopy. GMACS will be able to take a spectrum of anysimultaneous object coverage imaged of Balmer lines/break by LSST (365-656 nm) <2 Å resolution at Li 6708Å for age measurements; blue coverage (Ca HK) Dwarf Galaxy dynamics Stellar Abundances Redshift surveys (LSST, DES follow-up) Galaxy assembly, IGM/CGM studies Properties of Galaxies during Reionization Coverage of CaT (850 nm, R~5000); 3 km/s velocity precision, high stability. 20 FOV preferable R~5000, blue/red wavelength coverage (370-540 nm; CaT 850 nm) High multiplexing, slitlength requirement: source density will be ~50-60 arcmin -2. FOV as large as possible. Large simultaneous wavelength coverage to improve efficiency. R~3000 and redder wavelength coverage for absorption line studies of z > 1 galaxies. Very red coverage (>900 nm for Ly-α at z > 6.5), higher resolution and high multiplexing/fov helpful (~0.5-1 source/arcmin 2 )
The future of wide field survey spectroscopy, adapted from Jeff Newman. Disclaimer: dates are rough and preliminary. SnowPAC2018: Roadmaps to Wide Field Southern Spectroscopic Surveys In the landscape of future LSST (even DES) spectroscopic followup, there is a lot missing: Aperture Hemisphere The future
GMACS science: Thinking outside the box With ~100 nights, GMACS can Fully map Milky Way halo by measuring velocities and rough metallicities of all stars in known halo substructures (UFDs, streams, etc.) Spectroscopically train photometric redshifts to enhance DETF FOM (Newman Method) Measure the mass of the neutrino by measuring galaxy power spectrum at z > 2.5 With rapid response capability, GMACS Is uniquely able to followup any LSST faint transient Can acquire transient observations at the same time as primary science observations Possibilities are numerous, but only with appropriate coordination between partners/users
Thank you!