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VVDS: Towards a complete census of star formation at 1.4<z<~6

VVDS: Towards a complete census of star formation at 1.4<z<~6. Olivier Le Fèvre Laboratoire d’Astrophysique de Marseille With the VIMOS VLT Deep Survey team. Magnitude selected spectroscopic redshift survey Ultra-deep VVDS sample Ly  flux limited spectroscopic redshift survey

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VVDS: Towards a complete census of star formation at 1.4<z<~6

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  1. VVDS: Towards a complete census of star formation at 1.4<z<~6 Olivier Le Fèvre Laboratoire d’Astrophysique de Marseille With the VIMOS VLT Deep Survey team • Magnitude selected spectroscopic redshift survey • Ultra-deep VVDS sample • Ly flux limited spectroscopic redshift survey • Improved galaxy census

  2. Understanding galaxy evolution at z>1.4 requires a complete census • Star formation, mass assembly history, are derived from galaxy counts • Are we making a reasonably complete census of star-forming galaxies ? • Color pre-selection vs. flux selection • Hard job: only 3-4% of AB~25 galaxies are at z>1.4 Astronomy Astro-Physics

  3. Making a complete census LBG, BzK DRG, SMG, EROs, NB,… I, K, 3.6µm,… Em. line Seeing Hypotheses f(m,z) Simulations g(m,size, SB, color) g(m,size,SB,color): uncertain for faint high-z objects

  4. VVDS: magnitude limited samples VLT-VIMOS A total of ~1580 galaxies with 1.4<z<6.6 and spectroscopic redshifts Check http://cencosnew.oamp.fr/ for public data

  5. New Ultra-Deep sample • Magnitude selected IAB≤24.75 • 863 galaxies targeted with VLT-VIMOS • 262 re-observed from failed IAB≤24 • 18h integrations in blue + 18h integrations in red, 3600-9350A coverage • 86% complete

  6. High S/N Combined spectra Lyman-break

  7. « Bean counting » • Producing accurate redshift distributions N(z,m) • Completness of redshift measurements • Minimized with re-observed samples • Two independant observations • Reobserved objects with longer integration times • Tested with photometric redshifts

  8. VVDS IAB≤24 2005 80% complete Redshift distribution IAB ≤24 Uncorrected for incompletness

  9. VVDS IAB≤24, corrected 2009 96% complete Failed on first attempt IAB≤24 sample, now re-observed with secure z Redshift distribution IAB ≤24 Corrected for incompletnessusing highsuccess rate in re-observed samplewith 3700-9300A wavelength coverage and 4.5x exposure time

  10. Redshift distribution IAB ≤24.75 VVDS-Udeep IAB≤24.75 863 objects New ultra-deep sample z_median=1.4 86% complete Well into redshift desert because of the 3600-9350A coverage

  11. Aposteriori comparison spectroscopic vs. Photometric redshifts Spectacular agreement: High quality photometry trained on High quality spectroscopic redshifts LBG Ilbert et al., in prep.

  12. Galaxy number density at z~3 • Use N(z) • Corrected IAB≤24 • Uncorrected IAB≤24.75 ~2x more galaxies in magnitude limited survey than in LBG, for all mag IAB22 Confirms Le Fèvre et al. 2005 CENSUS IS DIFFICULT AT z~3 WORRISOME FOR z>3 Work in progress

  13. Use VVDS to check color-color selection: ugr (LBG z~3) Confirmed spectro-z z<2.5 and z>3.5 Confirmed spectro-z 2.7≤z≤3.5 Not-LBG LBG Exquisite photometry From CFHTLS VVDS spectro: Black: z<2.7 Green: stars 60% contamination 15% not selected Main source of uncertainty from color selection: the depth of photometry

  14. Census of LAE:The VVDS Ly emitters sample • Search for serendipitous emission in the slits of the VVDS Deep and Ultra-Deep observations • Use the large wavelength coverage to isolate Ly systems • Use the exact knowledge of the sky background to estimate the flux limit F() A complete flux limited LAE survey

  15. What are we looking for? VVDS main target Slits: 1”x5-20” Serendipitous Lya @ 1216Å Target spectrum  Photometrically invisible Lya emitter • 1200 slits, covering 3.3 arcmin2, 3500-9500Å, exp. times 65000s • 8000 slits, covering 22.2 arcmin2, 5500-9500Å, exp. times 16000s

  16. The LAEsample • Flux limit: ~2x10-18 erg.cm-2.s-1 • 86 Lya from UDeep blue • 25 Lya from UDeep red • 27 Lya from Deep • 66 spectroscopy main targets 204 emitters The largest LAE sample with spectroscopy confirmed z

  17. Combined spectra Ly emitters Lya line profile Asymetric, as expected Combined spectra

  18. 6 Ly emitters at 6<z<6.6

  19. Redshift and Luminosity distribution • UDeep blue • UDeep red • Deep First exploration at faint luminosities 1041 erg/s

  20. LAE Luminosity function No apparent evolution from z=2 to z=6.6 But evolution when including dust and IGM corrections we reach log(lum)=41erg/s: we can constrain  • Black: literature z=3-6 =1.75

  21. Star formation density from LAE If Lya emission is coming from Star Formation… • No correction for dust • No correction for IGM absorption • Constant SFD from z=2 to z=6 • Ly contributes to 20% of the SFD at z=2.5, 30% at z=5, >50% at z=6 Cassata et al., submitted

  22. Summary • Galaxy studies at z>1 require complete magnitude-selected deep spectroscopic surveys Star-forming galaxy census at z>1 is not complete yet • UV-continuum selection spectroscopic survey counts ~2x more galaxies at z~3 as compared to color-selection (LBG) Color-color selection has build-in inaccuracy • Faint Ly emitters with log(Ly )<42 are numerous, LF slope =1.7 at z~2-6 Ly SFRD is 30% of the total SFRD at z~3, becoming dominant at z~6 New deep redshifts surveys are required to make progress

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