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Next generation redshift surveys with the ESO-VLT

Next generation redshift surveys with the ESO-VLT. Olivier Le Fèvre, Laboratoire d’Astrophysique de Marseille. Today Instrumentation for surveys on the VLT Several surveys covering up to z~6 Tomorrow ? Need for massive surveys Need for new instrumentation ? Short term Long term.

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Next generation redshift surveys with the ESO-VLT

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  1. Next generation redshift surveys with the ESO-VLT Olivier Le Fèvre, Laboratoire d’Astrophysique de Marseille • Today • Instrumentation for surveys on the VLT • Several surveys covering up to z~6 • Tomorrow ? • Need for massive surveys • Need for new instrumentation ? • Short term • Long term

  2. Instrumentation for surveys at the VLT • Optical instruments • VIMOS-UT3: multi-slit 14x16 arcmin², 150 to 1000 slits (if 10arcsec long, R~220 to 2500) • FORS-UT2: multi-slit 7x7 arcmin², 100 slits max, red optimized • FLAMES:-UT4 multi-fiber, 130 fibers, 15 small IFUs • In dev.: MUSE (2011), 1 arcmin² IFU + adaptive optics • NIR instruments • Not really for surveys but for follow-ups • Missing a NIR-MOS • SINFONI: single object IFU cryogenic, JHK bands • ISAAC: long-slit cryogenic, JHK bands • In dev.: KMOS (2011), 24 IFUs, JHK bands

  3. VIMOS -VLT-UT3 A highly efficient high redshift machine in operations since 2002 on the VLT

  4. Multi-slit mode Low res. High res.

  5. Instruments for surveys at the VLT FLAMES=GIRAFFE+OzPoz 130 fibers, 0.4-1 microns FORS2, 0.4-1 microns 7x7 arcmin², 100 slits

  6. Instruments for follow-up from surveys SINFONI 3D-IFU 1-2.5 microns On-going: 150 VVDS galaxies 1<z<1.8

  7. On-going redshift surveys at the VLT • Several surveys covering up to z~6 • Wide and Deep [VIMOS]: VVDS aiming for up to 30deg² and 1.5x105 redshifts • Wide [VIMOS]: zCOSMOS (2 deg²) • Medium-deep [VIMOS, FORS2]: UDF (1 deg²) • Deep [VIMOS]: • GOODS, 7000 redshifts • zCOSMOS, 1.5<z<3, 15000 redshifts • Ultra-Deep: VVDS [VIMOS], GMASS [FORS2] • a few hundred sq.arcmin, a few thousand objects • Others • 3D integral field: VVDS-SINFONI, FLAMES • Other programs…

  8. VIMOS VLT Deep Survey • R~230, 5500-9300Å • ~50000 spectra today • Goal >20000 Deep and 100000 Wide

  9. VVDS redshift desert N(z): IAB22.5 , IAB24, IAB24.75 Magnitude selection only: complete census of the population, minimize apriori selection bias IAB≤22.5, <z>=0.55 IAB≤24 <z>=0.75 High redshift tail to z~4-5 22.5≤IAB≤24.75 <z>=1.4 High redshift tail to z~5 40% of galaxies with z>1.5

  10. VVDS-Wide, 35000 redshifts Measuring  at z=0.8, using (rp,) =0.7±0.24 From 8 deg² (Guzzo et al., submitted) 4 deg²

  11. VVDS-UltraDeep • Magnitude selected IAB≤24.75 • Toward a complete census • No apriori • ~50% of galaxies at z~3 are not LBGs ■ VVDS UDeep LBG Box

  12. Measuring galaxy evolution from the VVDS Distribution in LSS Luminosity / SFR / Mass evolution High redshift populations N(z) Reddest Galaxies to z~2 Luminosity Function Galaxy density field 1000 galaxies 1.4 < z < 5 Luminosity Density Correlation function SFR 1000 galaxies IAB≤24.75 Mass function 130 faint QSOs to z=5 Track evolution versus Environment, Luminosity, galaxy Type,…

  13. MB=-21 MB=-17 VVDS results Clustering Stellar mass Luminosity function to z~3 By type Vs. environment 40+ papers published so far Type density relation evol

  14. With VLT-VIMOS • Wide: 2 deg², 25000 spectra, IAB≤22.5, 0<z<1.2 • Deep: 1 deg², 15000 spectra, BzK+UGR selected 1.5<z<3 zCOSMOS On HST-COSMOS 2 deg² field 1.5<z<3 Combined spectra with Lya in emission vs; in absorption

  15. On-going redshift surveys at the VLT: summary • At z~1 : ~10 deg², ~100Mpc scales, several 104 redshifts, coming up: ~105 redshifts • At z~2-3: ~1-2 deg², ~50Mpc scales, a few hundred redshifts now, several 103 redshifts coming up • At z=4-6: A few tens of redshifts 20-100 smaller at z~1 in dz=0.2 than 2dFGRS-SDSS • Keep in mind the huge human effort needed • Currently VVDS, zCOSMOS require 1week, 2 people for 500 spectra • automated z measurement when 0<z<5 is not yet achieved

  16. Probing the Universe with spectroscopic surveys Understand galaxy formation and evolution Measure Cosmology parameters Understand LSS formation and evolution Towards reionisation z~15 SNIa Baryons oscillations ,8 … Large scales, >100 Mpc High redshifts z>~1-6 Very deep, M* at z~10 Small fields Several thousand objets Wide fields >10deg² Deep, M* at z~3 >10^5 objects Multi-object spectroscopy NIR-MIR 3D spectroscopy NIR-MIR Multi-object spectroscopy Multi- photometry, visible + near-IR Lensing, CMB, SnIa…

  17. Next surveys at the VLT: Test cases • “SDSS at z~1”: • 106 galaxies, 50-100 deg² • >200Mpc scales • AB~23 • All-sky survey to z~1 • A few 108 galaxies, 10000 deg² • “VVDS at z~3-6” • 105 galaxies, 25deg² • Extremely deep probe z~10 • A few hundred objects, AB~26

  18. 1. VIMOS VLT Large Survey SDSS at z~1 • “SDSS at z~1”: BAO++… (galaxies, clusters, QSOs) • 7x106 galaxies, 100 deg² • >200Mpc scales • AB~22.5 • 100 deg²: 4800h with VIMOS • 48 VIMOS pointings to cover 1deg² • 45 min integrations for IAB≤22.5 (85% completeness) + overhead • Need 480 nights= 5 years project @ 100n/y CAN BE DONE TODAY ! Dedicate VLT-UT3+VIMOS

  19. 2. ‘All-sky’ survey at z~1 • Requirements: • 10000 deg² (high galactic latitude) • z~0.5-1, IAB≤22.5 • 1 in 4 sampling • 5-10 years survey • Need 1000y with VIMOS: need to think of new instrument ! • Boost the multiplex gain

  20. 2. ‘All-sky’ survey at z~1 • Ground-based facility • Need ~104 simultanous redshifts in 1h to complete in 5-10y • 2x108 redshifts • Concepts: • WFMOS: on 8m, 1.75deg² field, 4000 fibers, need ~800 nights • MEGAMOS: on the VLT, >1.5deg², 10000 spectra with micro-mirrors / shutters. Not easy: feasibility study • Space-based facility • Submitted to ESA ‘Cosmic-Vision’: SPACE mission • telescope 1.5m, 0.5deg field, 10000 spectra with micro-mirrors • Can do 0.5x109 redshifts in 3y mission, down to H=23 (15 min)

  21. 3. VVDS-like at z=3-6 • Requirements: • U, B, V and R-band Lyman-break and Ly- selection at IAB≤25 • 25 deg² to probe >100Mpc and beat cosmic variance • 105 spectra for stats • With existing facilities • VIMOS: • need 20h integrations • 4000h=500 nights program • Space-based facility • SPACE-like instrument: deep probe of several 105 z CAN BE DONE TODAY ! Dedicate VLT-UT3+VIMOS

  22. 4. Ultra-deep probe z=10 • Requirements: • H~26 • A few hundred objects • Field: guess, depends on the number density • With existing facilities • Not possible with 8m (?) • Need space (beat sky and thermal background) • Future facilities • ELT multi-slit and multi-IFU • SPACE-like instrument: telescope 1.5m, 0.5deg field, 10000 spectra with micro-mirrors • JWST

  23. Summary Next generation surveys with the VLT • Dedicate VLT for very large redshift surveys • Motivate the community • Short term: dedicate VLT-VIMOS to a few large surveys • z~1, 106 redshifts • z~3-6, 105 redshifts • Long term: New instrument on 8m very wide field MOS with 10000 slits/fibers • Note: further develop automation of z measurement at high z. Not trivial

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