Wide-field astronomy with GMT and MANIFEST

Transcription

1 Wide-field astronomy with GMT and MANIFEST Matthew Colless Anglo-Australian Observatory (to 30 June) Australian Astronomical Observatory (from 1 July) but always! Challenges for GMT, Swinburne, June 2010

2 MANIFEST team The MANIFEST team at the AAO is: Matthew Colless (Principal Investigator) Ian Saunders (Project Manager) Will Saunders (Instrument Scientist) Guy Monnet (Instrument Scientist) Andrew Hopkins (Science Analysis) Michael Goodwin (Instrument Modelling) Jeroen Heijmans (Mechanical Analysis) Jurek Brzeski (Mechanical Design) Tony Farrell (Software Design)

3 Size isn t everything GMT 25m TMT 30m E-ELT 42m GMT is the smallest ELT, but it has the (equal) largest FoV GMT cannot beat the other ELTs at D n science, but it can dominate wide-field and survey astronomy

4 MANIFEST MANIFEST = MANy Instrument FibEr SysTem is the means by which GMT can dominate AΩ astronomy MANIFESTo: any GMT instrument should have versatile scientific access to the full focal plane MANIFEST is a telescope facility not an instrument (i.e. MANIFEST is to the focal plane as AO is to the PSF) What MANIFEST offers GMT is... a number of wholly new and distinct capabilities increased efficiency, survey speed & versatility a leading role over a wide swathe of science

5 Focal plane versatility What does focal plane versatility really mean? Access to the full 20 (24?) arcmin field of view of GMT Choice of the focal plane regions to be observed Ability to suit the number, size, type & location of the focal plane aperture(s) to the scientific application single fibers to maximise multiplex and/or field of view monolithic IFU or multi-ifus for spatially resolved spectra fiber sizes matched either to natural seeing or to the PSF delivered by AO (especially GLAO; also, potentially, MOAO) Reformatting to efficiently pack spectra on detectors Opportunities for additional processing of the light (e.g. OH-suppression to reduce NIR background)

6 MANIFEST paradigm The MANIFEST paradigm is... Do no harm the proposed fiber system should not prevent any instrument working in its native mode Add value the system should allow instruments to access the full GMT FoV with little/no loss of efficiency Add function the system should wherever possible provide additional functionality, over and above FoV This paradigm requires that MANIFEST is... Switchable readily put into (taken out of) operation Modular each new instrument is just a new module Upgradeable new functionality via minimal upgrades

7 MANIFEST concept MANIFEST is a fiber positioner to feed all of GMT s natural seeing or GLAO-fed spectrographs; it far exceeds the GFFS Call for Proposal requirements Design has ~2000 autonomous fiber-positioning 'starbugs' with various aperture geometries incl. single-aperture, image-slicing, multiple IFU sizes The design is modular, connecterised, versatile & makes extensive use of existing telco technology AAO is prototyping the novel technologies: fiber tapers, starbugs, hexabundles & cooled fiber slit (all of which have workable existing alternatives)

8 Schematic Telescope view of MANIFEST system MANIFEST Instruments GMACS G-CLEF NIRMOS!

9 MANIFEST layout Stowed position

10 MANIFEST installed in GMT s Gregorian Instrument Assembly MANIFEST in active position GMACS GMACS MANIFEST in stowed position NIRMOS

11 Fiber positioner MANIFEST uses the hanging starbug concept for fiber positioning: elegant, fast, modular, versatile, cheap! Ring-shaped magnet Magnetic piezo-actuated discrete stepper Curved glass field plate Hanging fibers Untried: prototyping in progress; pick-&-place backup

12 Fiber innovations Fiber tapers for changing f-ratio OH-suppression fibers for eliminating >95% of J & H background! Hexabundles for IFUs

13 MANIFEST throughput The small fiber losses (above 400nm) offset by having all spectra at superblaze angle of VPH gratings Excludes aperture losses

14 MANIFEST feed formats GMACS FoV 1200 single fibers x 7-fiber slicer x 37-fiber IFUs x 1200-fiber IFU x 10 x NIRMOS 450 single fibers x 7-fiber slicer x 37-fiber IFUs x 900-fiber IFU 7.5 G-CLEF 50 single fibers x 7-fiber slicer 0.75

15 Survey speed gains Survey speed is the inverse time taken to cover, at fixed S/N, sky area A at target density σ.... speed ~ ε.[a/ω] -1.[σΩ/N] -1 where ε=efficiency, Ω=field of view, N=multiplex, and [..] means the next larger integer. Limiting cases... Field-limited if N>σΩ: speed ~ ε.ω/a ~ ε.ω Multiplex-limited if N<<σΩ: speed ~ ε.n/(aσ) ~ ε.n Assuming MANIFEST accesses the the full 20 GMT field and has minimal impact on efficiency...

16 Survey speed gains Survey speed gains: about 2-4 for GMACS/NIRMOS and 10 (all orders) or 50 (single order) for G-CLEF Instrument Field-limited gain Multiplexlimited gain GMACS ~2 ~2 NIRMOS ~4 ~2 G-CLEF (all orders) ~10 ~10 G-CLEF (single order) ~50 ~50

17 Qualitative gains Image-slicing provides greatly increased spectral resolution without loss of wavelength coverage or efficiency; gains are ~3x w.r.t natural seeing; limited only by 2-pixel sampling Multiple deployable IFUs offer either greater light grasp for spatially extend targets or spatially resolved spectroscopy (with increased resolution, as for image-slicing) OH-suppression is a goal for MANIFEST, and would yield 20-40x improvement in the sensitivity of J and H-band spectroscopy by eliminating the night sky lines; this allows working at lower dispersions, so reducing integration times needed to beat read-noise; note that the uncertainty is not whether OH-suppression works, but whether it s affordable

18 50 x 10 x Mapping MANIFEST capabilities to GMT science cases!

19 MANIFEST science cases GMACS + NIRMOS NIRMOS GMACS NIRMOS G-CLEF G-CLEF GMACS GMACS GMACS + G-CLEF NIRMOS

20 Galaxy evolution - 1 Star-formation and the origin of the Hubble sequence... Multi-object, spatially-resolved spectroscopy is needed to study the SFR, metallicities, dynamics of galaxies of all types at z>1 MANIFEST provides fiber IFUs for NIRMOS (100 for GMACS) Simulation of the Antennae at z~3.3 with various PSFs... natural seeing (0.5 ) MCAO (nearly D.L.) GLAO (0.15 ) GLAO+MANIFEST+NIRMOS could obtain 37-pixel IFU resolved spectroscopy for 30 z~3 galaxies simultaneously at R~3000 with spatial sampling of 0.25 ; if OH-suppression, gains of 20-40x

21 Mass-metallicity relation in galaxies to high z... With NIRMOS can use the [OIII] line to z~3.5 Large mass-defined samples (many 100s) Fundamental measure of star-formation history Galaxy evolution - 2 MANIFEST+NIRMOS gives 2-4x the survey speed of NIRMOS in native mode Mass-metallicity relation at z~0.7 from CFRS and GDDS

22 The evolution of galaxy masses and the total stellar mass density... Galaxy evolution - 3 Detect galaxies to 0.1M* at z>3 MANIFEST provides 2-4x the survey speed of GMACS or NIRMOS alone

23 Stellar IMF surveys For sparse stellar groups, where survey speed ~ field of view, MANIFEST is 2x faster than GMACS and 4x faster than NIRMOS For dense stellar clusters, where survey speed ~ multiplex, MANIFEST is 2x faster than GMACS and NIRMOS Trapezium at 150 pc with HST/NICMOS Simulated GMT H-band at 100 kpc

24 Mapping dark matter Measure DM distribution from velocity fields for 1000s of testparticles by various methods... Monolithic IFU spectra of cd galaxy outskirts to probe the small-scale (<50 kpc) DM distribution Wide-field MOS for PNe in galaxy clusters for large-scale (>250 kpc) DM MANIFEST provides capabilities to do both, giving GMACs up to 100 small IFUs & a large monolithic IFU

25 Clustering evolution Galaxy surveys to measure Baryon Acoustic Oscillations at high (z>3) redshifts Survey outlined in the GMT Science Case uses GMACS to target up to 5x10 5 galaxies over 50 deg 2 MANIFEST provides a factor 2 improvement in survey speed over GMACS alone

26 High-z SNe and GRBs Monolithic IFU with GLAO can map z>1 SNe hosts SNe/SFR as function of galaxy morphology/mass PSF IFU to localise high-z GRBs measure light curves Gunn-Peterson troughs MANIFEST offers monolithic IFU with GLAO resolution (i.e PSF) in NIR ACS images of z>1 SN1a

27 IGM tomography IGM tomography: reconstructing the 3D small-scale structure of the IGM at high redshifts by very densely sampling the Lyα forest GMT can see Lyα forest in faint (so dense) QSO/AGN/LBG samples Program needs R>5000 and so GMACS resln is too low unless slits << seeing LBGs extended sources: makes problem worse Gemini 10h GMT 10hr Simulated LBG spectrum (z=4) at R=10,000 Lyα forest MANIFEST s image-slicing and deployable IFUs allow all available targets to be observed with R~8000, while also doubling the FoV; the overall gain in IGM tomography survey speed is a factor of 10

28 Galactic Archeology Galactic archeology uses chemical tagging of stars to trace the formation history of the Milky Way & nearby Local Group galaxies G-CLEF yields high-resolution (R~25,000) spectra with S/N>30 for many RGB stars in tidal streams in the MW halo or LG members Requires stars over large areas to delineate streams, measure ages and chemical gradients This project is not feasible without MANIFEST, which offers up to 50 simultaneous targets with G-CLEF over the full GMT field

29 MANIFEST & GMT science The fiber feed formats map variously to GMT science cases Formats useful in >1 case: single fibers (4), image-slicers (4), small IFUs (3) and monolithic IFUs (2) 50 x 10 x GMACS NIRMOS G-CLEF!

30 MANIFEST capability gains Full 20 arcmin GMT field of view available to all instruments Survey speeds increased for single-aperture observations by a factor of 2 for GMACS and by a factor of 2-4 for NIRMOS Multiplexed image-slicing increases spectral resolution by factors of between 3x and 8x Multiplexed, deployable IFUs in a variety of sizes Efficient packing of spectra on each instrument s detectors Overall efficiency >90% at >400nm; all objects use VPH gratings at superblaze angle, compensating for other throughput losses Potential to use of multiple instruments simultaneously Allows gravity-invariant spectrographs OH suppression over full J+H bands is design goal MANIFEST makes GMT the most powerful ELT for survey astronomy

31 Cost-effectiveness The nominal operating cost of GMT is ~$100k/night (similar to running the two Kecks) Thus the monetised quantitative gains are... GMACS: a factor of 2 in survey speed = $50k/night NIRMOS: a factor of 2-4 in survey speed = $50-75k/night If MANIFEST is used 50% of time with GMACS/NIRMOS, and they are used 50% of time on GMT, saving is >$4M p.a. Cost of MANIFEST returned in ~3 years! Alternatively, MANIFEST turns GMT into 2-4 telescopes, at least for survey science driven by numbers or area. Plus qualitative gains: increased resln, OH-suppression, etc.

32 Strategic advantages Strategic advantages of MANIFEST include... It greatly enhances the science cases for the planned GMT instruments without making major modifications It adds powerful new functionality at modest extra cost (higher resolution, hexabundle IFUs, OH-suppression...) It is relatively cheap and fundamentally modular, so it can be scoped to fit the GMT instrument budget and readily upgraded to work with new instruments It plays to Australia s strength in survey astronomy, complementing both existing and planned facilities It establishes GMT as the dominant wide-field ELT, with 1.8x AΩ of its nearest competitor, TMT+WFOS

33 Future of MANIFEST MANIFEST is not an instrument but a telescope facility, and so is not one of the six instrument concept studies However the GMT Science Advisory Committee has recognised the great potential of MANIFEST for GMT science and recommended that it be further developed The GMTO Board has approved funding for a feasibility study that will also be funded by Australia s EIF funding Expect to start in July and go through February 2011 Goals of the feasibility study: Retire major technical risks to MANIFEST (mainly the starbugs) Coordinate with other instruments to ensure compatibility

34 50 x 10 x Mapping MANIFEST capabilities to GMT science cases!