HETDEX SURVEY FOR LYMAN ALPHA EMITTERS AT 2<z<4

1. HETDEX SURVEY FOR LYMAN ALPHA EMITTERS AT 2<z<4 Guillermo A. Blanc The University of Texas at Austin COLABORATORS: UT : Karl Gebhardt, Gary Hill, Eichiro Komatsu, Phillip MacQueen, Joshua Adams, Lei Hao MPE, Garching: Niv Drory, Ralf, Bender, Ralf Koehler Penn State: Caryl Gronwall, Robin Ciardullo HETDEX Collaboration: UT, MPE, Penn State, AIP, Texas A&M, McDonald Observatory

2. OUTLINE • HETDEX Survey • VIRUS • The HETDEX Pilot Survey: • VIRUS-P • Observations and Data Reduction • Detection of Emission Line Galaxies • Results: • Selection of LAEs • Predicted vs. Observed Redshift Distribution

3. HETDEX • Hobby-Eberly Telescope Dark Energy eXperiment • Measure w(z)=pDE(z)/ρDE(z) at 2<z<4 using Baryonic Acoustic Oscillations (BAO) • Power spectrum of the spatial distribution of 1,000,000 LAEs over a volume of 9 Gpc3

4. HETDEX • How do you find 1,000,000 LAEs? You use a VIRUS Visible Integral-field Replicable Unit Spectrograph 150 replicable IFU = 40 arcmin2 FOV, 37000 fibers (D=1.5”)

5. INTEGRAL FIELD SPECTROSCOPY The active galaxy NGC1068, imaged using an Integral Field Unit Image: Stephen Todd, ROE and Douglas Pierce-Price, JAC.

6. IFS vs. NARROW-BAND • NB surveys only sample a very thin range in redshift space. • Integral Field Spectroscopy samples much larger volumes for a given area on the sky. • MUSYC: • Flux limit = 1.5·10-17 ergs/s/cm2 • Surface density = 0.16 arcmin-2 • Δz = 0.04 • VIRUS-P Pilot Survey: • Flux limit ~ 6·10-17 ergs/s/cm2 • Surface density = 1.24 arcmin-2 • Δz = 1.9 • van Breukelen et al. 2005 (VIMOS) • Flux limit = 1.4·10-17 ergs/s/cm2 • Surface density = 17.3 arcmin-2 • Δz = 2.9

7. VIRUS-P • VIRUS Prototype IFU • 1.9’x1.9’ FOV at HJST 2.7m • 1/3 filling factor • Largest FOV of any existent IFU • 4.1’’ diameter fibers on sky • 3500-5800Å wavelength range • R=1000 @ 5000Å

8. The VIRUS-P Pilot Survey • 148 arcmin2 surveyed on COSMOS, GOODS-N and MUNICS-S2 fields • Fields selected to have deep multi-wavelength broad-band imaging • 6 position dither pattern ensures good field coverage • 5σ flux limit of ~6x10-17 erg/s/cm2 for a point-source emitting and unresolved line

9. Reduced Frame • Final combined 1hr exposure • Collapse into 1D spectrum • Ready to search for emission lines

10. DETECTION OF EMISSION LINES • GROW DETECTION UNTIL S/N STOPS INCREASING • POSITION GIVEN BY FIRST MOMENT OF LIGHT DISTRIBUTION • DETECTION: S/N > 5, FWHM > 3 Å

11. PRELIMINARY ANALYSIS • We have analyze 12 pointings (40 arcmin2) of data in the COSMOS field. • 99 unique emission line sources detected. • COSMOS has publicly available deep broad-band Subaru imaging. • Good to look for counterparts

12. SPECTRAL CLASSIFICATION • 2 step classification: • Classification based solely on the spectrum • Use of broad band fluxes of counterparts to set EW limits on ambiguous sources Noll et al. 2004

13. SPECTRAL CLASSIFICATION • Spectrum only: • Based in the presence of other lines at the corresponding wavelengths. • LAEs should not show other lines but Lyα • Single emission line spectra are harder to classify • For an [OII] emitter at z>0.18, the [OIII] doublet falls outside the wavelength range LAE if λ<4397Å ([OII]λ3727 at z=0.18) Ambiguous if λ>4397Å

14. SPECTRAL CLASSIFICATION • After first classification: • 30 LAEs • 9 [OII]λ3727 Emitters • 5 [OIII]λ5007 Emitters • 3 Hβ Emitters • 1 AGN • 51 ambiguous classifications • 51 out of 99 (~50%) objects in the sample can not be classified based only on the spectrum.

15. r+ BAND PHOTOMETRY AND EW CUT • Continuum limit for which EWREST>60Å if line is [OII] • Objects with all counterparts fainter than limit are classified as LAEs • Objects with single counterparts showing obvious low-z morphology are classified as [OII] Emitters • Ambiguous cases are left unclassified

16. FINAL CLASSIFICATION • After final classification: • 45 LAEs • 35 [OII]λ3727 Emitters • 5 [OIII]λ5007 Emitters • 3 Hβ Emitters • 1 AGN • 10 ambiguous classifications • The fraction of ambiguous classifications went down from 50% to 10% by the use of broad-band imaging. • Flux Calibration will reduce it further. EW measurements, not limits. • HETDEX will need a single-band imaging survey. With current wide field imagers this could be done in ~40 nights.

17. LYMAN ALPHA EMITTERS

18. LOW REDSHIFT AND UNCLASSIFIED SOURCES

19. REDSHIFT DISTRIBUTION L* Evolution Φ* Evolution No Evolution

20. CONCLUSIONS • 45 to 55 LAE sample over 35 arcmin2 to a median flux limit of ~6x10-17 ergs/s/cm2. • ~200 LAE expected over the whole pilot survey area. • VIRUS-P IFU samples 50 times more volume per arcmin2 than narrow-band surveys. • Large FOV makes IFU LAE searches efficient. • Number of sources agrees with predictions from previous measurements of the Lyα LF of galaxies.

21. CONCLUSIONS • Pilot Survey Science: • Evolution of the Lyα LF • Large scale clustering and bias • Physical properties of LAE (SED fitting) • Candidates for NIR Hα spectroscopy at 2 < z < 2.5 : Lyα/Hα studies • Redshift dependence of LAE properties • HETDEX Science • VIRUS will be the largest IFU in the world and will be commissioned by the end of 2010. HETDEX will detect ~1,000,000 LAE in 100 nights. • HETDEX will measure w at z~3 with ~1% accuracy and measure evolution if DE≠Λ and w(z) evolves more than a 1%. • All Pilot Survey science with MUCH BETTER statistics. • Stacked high S/N spectra of LAE in bins containing ~105 objects. • LAB search (expect 103 – 104 sources) . • Pop III search by a HeIIλ1640 maximization stacking. • www.hetdex.org