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Ultra- Deep galaxy surveys with DIORAMAS@EELT the early build -up of galaxies

Ultra- Deep galaxy surveys with DIORAMAS@EELT the early build -up of galaxies. Olivier Le Fèvre With the DIORAMAS team (F, IT, CH, SP). Galaxy populations at and after reionisation. What do we need ? Find the “first” galaxies: exciting ! Journal headlines !

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Ultra- Deep galaxy surveys with DIORAMAS@EELT the early build -up of galaxies

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  1. Ultra-Deepgalaxysurveyswith DIORAMAS@EELTthe earlybuild-up of galaxies Olivier Le Fèvre With the DIORAMAS team (F, IT, CH, SP)

  2. Galaxy populations at and afterreionisation • What do we need ? • Find the “first” galaxies: exciting ! Journal headlines ! • Study the population of galaxies as it quickly evolves: astrophysics ! • Requires large surveys • Search for objects and then study them • Several time steps, types, environment: need thousands of objects • Surveys are more than ever the backbone of exploration • Statistical robustness

  3. Understandinggalaxy formation and evolutionrequiresmulti-stepsurveys A severalstepprocess • Search for objects: need to findobjectsbeforedoingphysics ! • Estimate the meanproperties: N(z), luminosity, gas/stellar masses, SFRD, morphology, clustering, …. assemble representativesamples • Isolatewelldefinedsub-populations for detailedstudies, e.g. kinematics • Infer a scenario & compare to models / simulations Deep multi-band imaging Large multiplex MOS IFU, AO-imaging, high-resspectra… Instrument flow Followed by all major surveys:CFRS, DEEP2, VVDS/MASSIV, IMAGES, LBG/SINS, zCOSMOS…

  4. GalaxyredshiftsurveysWhatis to beexpectedwhen EELT starts ? z<2 “all sky” coverage from EUCLID: 50 million spectroscopic redshifts • 2<z6 willstillbeunder-explored: • ~20 sq.deg • ~50000 zspec • Not enough for a comprehensivepicture • 6<z<10+: HST then JWST starting 2018 • ~1 sq.deg • 1000 zspec? • Not enough for robuststatistics • Not enough for welldefinedcase studies

  5. Finding first light objectsz>6.5 What are we looking for ? • Very faint objects AB>26.5 • Relatively sparse: 0.1 to 1 object per arcmin² per Δz=1 • The IGM will cut their observed flux below Ly • Main signatures: Ly-dropout and Ly emission • Need to sample from very rare bright objects to more numerous small building bricks (still rare on the plane of the sky) • At z>6.5 all the information is in the NIR Careful: • Take predictions on number density with caution (see historical perspective) Expect the unexpected… Keep a large parameter space for instruments

  6. MOS(s) on the VLT MOS: a fundamentalleapforward in instrumentation All major telescopes have one or more MOS VLT: 5-6 MOS flavors To cover a consistent parameter (discovery) spaceweneedat least 2 of these, ideallycombining modes, on the EELT

  7. 2 imaging-multi-slit MOS in the top 3 @VLT • Demonstrates « work-horse » versatile use • Galactic and Extra-Galactic Science • VLT science output isdominated by MOS ! FORS2 VIMOS

  8. Select the sample • Magnitudes, colors, NB... • Multi-slit Spectroscopy • Spectral features • Redshift • The best performances • High sky subtraction accuracy 0.1% Power of imaging-MOS • Multi-band imaging • Positions, magnitudes, shapes Main target, z=1.02 SerendipitousLyman z=4.3

  9. led to DIORAMASinstrument concept – phase A study • High multiplex MOS withslits • Imaging mode • Use EELT naturalseeing or GLAO-correctedbeam • Instrument concept accomodatesboth • Widefield: 6.8x6.8 arcmin² • 0.37-1.6 microns A versatile instrument

  10. DIORAMAS Opto-mechanicallayout

  11. DIORAMAS design parameters High throughput: 30% VIS, 45% NIR (with detector) Excellent image quality: 150 mas 80% encircledenergy Gain @1µm 10-25 compared to JWST-NIRSPEC: x5 multiplex, x2.5-5 FOV, at equivalent depth/unit time

  12. Wide field, multi-mode Multi-slitR~300 High multiplex 480 slits giJ Imaging VIS VIS NIR NIR >30,000 sources in 7’x7’ to rAB=29.8 JWST-NIRSPEC JWST-NIRCAM 12

  13. Wide field, multi-mode Multi-slitR~3000 High multiplex: 160 slits giJ Imaging VIS VIS NIR NIR >30,000 sources in 7’x7’ to rAB=29.8 JWST-NIRSPEC JWST-NIRCAM 13

  14. MOS spectroscopy at the EELT“extragalactic” science Need 2 MOS flavors A powerfulcombinationfor high-z: Imaging-MOS and multi-IFU+AO 3D IFU-MOS Imaging-MOS DIORAMAS

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