Next generation redshift surveys with the ESO-VLTTodayInstrumentation for surveys on the VLTSeveral surveys covering up to z~6

Tomorrow ?Need for massive surveysNeed for new instrumentation ?Short termLong term

Olivier Le Fvre, Laboratoire dAstrophysique de Marseille

Instrumentation for surveys at the VLTOptical instrumentsVIMOS-UT3: multi-slit 14x16 arcmin, 150 to 1000 slits (if 10arcsec long, R~220 to 2500)FORS-UT2: multi-slit 7x7 arcmin, 100 slits max, red optimizedFLAMES:-UT4 multi-fiber, 130 fibers, 15 small IFUsIn dev.: MUSE (2011), 1 arcmin IFU + adaptive opticsNIR instrumentsNot really for surveys but for follow-upsMissing a NIR-MOSSINFONI: single object IFU cryogenic, JHK bandsISAAC: long-slit cryogenic, JHK bandsIn dev.: KMOS (2011), 24 IFUs, JHK bands

VIMOS -VLT-UT3A highly efficient high redshift machine in operations since 2002 on the VLT

Multi-slit modeLow res.High res.

FLAMES=GIRAFFE+OzPoz130 fibers, 0.4-1 micronsFORS2, 0.4-1 microns7x7 arcmin, 100 slits Instruments for surveys at the VLT

SINFONI3D-IFU1-2.5 microns Instruments for follow-up from surveysOn-going: 150 VVDS galaxies 1

On-going redshift surveys at the VLTSeveral surveys covering up to z~6Wide and Deep [VIMOS]: VVDS aiming for up to 30deg and 1.5x105 redshiftsWide [VIMOS]: zCOSMOS (2 deg)Medium-deep [VIMOS, FORS2]: UDF (1 deg)Deep [VIMOS]: GOODS, 7000 redshiftszCOSMOS, 1.5

VIMOS VLT Deep SurveyR~230, 5500-9300 ~50000 spectra todayGoal >20000 Deep and 100000 Wide

Field

IAB

N(z): IAB22.5 , IAB24, IAB24.75Magnitude selection only: complete census of the population, minimize apriori selection biasIAB22.5, =0.55IAB24=0.75High redshift tail to z~4-522.5IAB24.75=1.4High redshift tail to z~540% of galaxies with z>1.5

VVDS-Wide, 35000 redshifts4 degMeasuring at z=0.8, using (rp,)=0.70.24From 8 deg (Guzzo et al., submitted)

VVDS-UltraDeepMagnitude selected IAB24.75Toward a complete censusNo apriori~50% of galaxies at z~3 are not LBGs VVDS UDeepLBG Box

Measuring galaxy evolution fromthe VVDSDistribution in LSSN(z)Galaxy density fieldHigh redshift populationsReddest Galaxies to z~2130 faint QSOs to z=51000 galaxies 1.4 < z < 5Luminosity / SFR / Mass evolutionLuminosity FunctionTrack evolution versus Environment, Luminosity, galaxy Type,Correlation functionLuminosity DensitySFRMass function1000 galaxies IAB24.75

VVDS results40+ papers published so farClusteringStellar massType density relation evolLuminosity function to z~3By typeVs. environment

zCOSMOSWith VLT-VIMOSWide: 2 deg, 25000 spectra, IAB22.5, 0

On-going redshift surveys at the VLT: summaryAt z~1 : ~10 deg, ~100Mpc scales, several 104 redshifts, coming up: ~105 redshiftsAt z~2-3: ~1-2 deg, ~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 neededCurrently VVDS, zCOSMOS require 1week, 2 people for 500 spectraautomated z measurement when 0

Probing the Universewith spectroscopic surveysUnderstand galaxy formation and evolutionTowards reionisation z~15Very deep, M* at z~10Small fieldsSeveral thousand objetsUnderstand LSS formation and evolutionLarge scales, >100 MpcWide fields >10degDeep, M* at z~3>10^5 objectsHigh redshifts z>~1-6Multi-object spectroscopyNIR-MIRMulti-object spectroscopy3D spectroscopyNIR-MIRMeasure Cosmology parametersSNIaBaryons oscillations,8Lensing, CMB, SnIaMulti- photometry, visible + near-IR

Next surveys at the VLT: Test casesSDSS at z~1: 106 galaxies, 50-100 deg>200Mpc scalesAB~23All-sky survey to z~1A few 108 galaxies, 10000 degVVDS at z~3-6105 galaxies, 25degExtremely deep probe z~10A few hundred objects, AB~26

1. VIMOS VLT Large Survey SDSS at z~1SDSS at z~1: BAO++ (galaxies, clusters, QSOs)7x106 galaxies, 100 deg>200Mpc scalesAB~22.5100 deg: 4800h with VIMOS48 VIMOS pointings to cover 1deg45 min integrations for IAB22.5 (85% completeness) + overheadNeed 480 nights = 5 years project @ 100n/y

CAN BE DONE TODAY !Dedicate VLT-UT3+VIMOS

Requirements:10000 deg (high galactic latitude)z~0.5-1, IAB22.51 in 4 sampling5-10 years surveyNeed 1000y with VIMOS: need to think of new instrument !Boost the multiplex gain

2. All-sky survey at z~1

Ground-based facilityNeed ~104 simultanous redshifts in 1h to complete in 5-10y2x108 redshifts Concepts: WFMOS: on 8m, 1.75deg field, 4000 fibers, need ~800 nightsMEGAMOS: on the VLT, >1.5deg, 10000 spectra with micro-mirrors / shutters. Not easy: feasibility studySpace-based facilitySubmitted to ESA Cosmic-Vision: SPACE missiontelescope 1.5m, 0.5deg field, 10000 spectra with micro-mirrorsCan do 0.5x109 redshifts in 3y mission, down to H=23 (15 min)

2. All-sky survey at z~1

3. VVDS-like at z=3-6Requirements:U, B, V and R-band Lyman-break and Ly- selection at IAB2525 deg to probe >100Mpc and beat cosmic variance105 spectra for statsWith existing facilitiesVIMOS: need 20h integrations 4000h=500 nights program Space-based facilitySPACE-like instrument: deep probe of several 105 z

CAN BE DONE TODAY !Dedicate VLT-UT3+VIMOS

4. Ultra-deep probe z=10Requirements:H~26A few hundred objectsField: guess, depends on the number densityWith existing facilitiesNot possible with 8m (?)Need space (beat sky and thermal background) Future facilitiesELT multi-slit and multi-IFUSPACE-like instrument: telescope 1.5m, 0.5deg field, 10000 spectra with micro-mirrorsJWST

Summary Next generation surveys with the VLTDedicate VLT for very large redshift surveysMotivate the communityShort term: dedicate VLT-VIMOS to a few large surveysz~1, 106 redshiftsz~3-6, 105 redshiftsLong term: New instrument on 8m very wide field MOS with 10000 slits/fibersNote: further develop automation of z measurement at high z. Not trivial