Probing Very High Redshift Galaxies with Gravitational Telescopes

1. Probing Very High Redshift Galaxies withGravitational Telescopes Danka Paraficz Jean Paul Kneib (Marseille), Johan Richard (Lyon) and Benjamin Clement (Arizona)

2. Reionization-Motivation • Recent WMAP results: the first building blocks of the Universe at redshifts up to z = 9−13 (Komatsu et al. 2008) • The end of this epoch is at z = 6.0−6.5 from the spectrum of high redshift quasars (Fan et al. 2006). • No clear confirmation (spectroscopic) of a galaxy at z > 7 • The detected z <7 population appears to be just barely able to provide the photons required to reionize the Universe • Contribution of early star formation to reionization • what were the objects that reionized the IGM? • what is the redshift distribution of the reionizing systems?

3. Lyman-Break-TechniqueLyman α =1215.67Åλo=(1+z)λi

4. Lyman-Break-TechniqueLyman α =1215.67Åλo=(1+z)λi

5. Constraints-Needle in a Haystack • Selection Criteria for z-dropouts: • >5 sigma detections in J or H, • z-J > 0.8, • J-H < 1.2 • No Detection in deep B, V, i data <2 sigma • z-dropouts z~6.4-7.3 • Remove sources with point source morphologies in the z-band (to eliminate brown dwarfs) ??? 0.15” PSF size in the F850LP –physical size for z~7 is >1 kpc!! • Rejecting spurious sources diffraction spikes of stars etc

6. Our data - HST and SpitzerWFC3+ACS+IRAC

7. Our data - HST and SpitzerWFC3+ACS+IRAC 15 filters 5 filters

8. Our data - HST and SpitzerWFC3+ACS+IRAC 15 filters 5 filters

9. Gravitational Telescopes-10 most massive Galaxy Clusters A1835 • This parameter provides an estimate of the extension of the strongly magnified area in the image plane. • This value quantifies the power of a gravitational telescope to magnify background sources. • The farther the cluster the smaller its magnifying power A370 A773

10. Number of high-z candidates with the magnitude limit

11. Gravitational Telescopes - Results A1835 Dropout candidates: ~9 galaxies z>7.5 ~18 galaxies z>7 ~30 galaxies z>6.5 3J-dropout (z>8.0) A370 A773

12. Gravitational Telescopes - Results A1835 A370 A773

13. Gravitational Telescopes - Results A1835 A370 A773

14. Gravitational TelescopeLensing or not lensing ? • Advantages: • - boosts the total flux by increasing the observed size of background sources (constant surface brightness) • - efficient for unresolved sources • multiple images configuration gives a hint on z

15. Gravitational TelescopeLensing or not lensing ? z=7.0 What really happens What we observe • Advantages: • - boosts the total flux by increasing the observed size of background sources (constant surface brightness) • - efficient for unresolved sources • multiple images configuration gives a hint on z

16. Gravitational TelescopeLensing or not lensing ? z=7.0 • Lensing introduces two opposite trends • Advantages: • - boosts the total flux by increasing the observed size of background sources (constant surface brightness) • - efficient for unresolved sources • multiple images configuration gives a hint on z • Drawbacks: • Effective area smaller in the source plane (compensate by observing more clusters) • Need to estimate the magnification to correct it (good lens model)

17. Gravitational TelescopeLensing or not lensing ? • Advantages: • - boosts the total flux by increasing the observed size of background sources (constant surface brightness) • - efficient for unresolved sources • multiple images configuration gives a hint on z • Drawbacks: • Effective area smaller in the source plane (compensate by observing more clusters) • Need to estimate the magnification to correct it (good lens model)

19. MS0451-arcDirector’s Discretionary Time MS0451

20. X-shooter spectroscopic dataof the MS0451-arcDirector’s Discretionary Time z~6.8 z~7.8

21. Other candidates Bullet F850LP F110W F160W

22. X-shooter spectroscopic follow-up Candidate Ly Emitters 2 h per target 20 targets 9 clusters

23. What about the Reionization?Luminosity function Brant Roberson et al Nature 2010

24. Summary • Strong lensing surveys are finding an abundant population of candidate faint Ly- emitters at z~6.5-8.5 with SFR <1 M yr-1 a population which may contribute significantly to reionization. • Implied densities of z~9 LAEs still very uncertain, but if correct, would require increase in Ly- photon output per unit halo mass from z~6. • Even with conservative assumptions, new instruments should result in reasonably large samples of galaxies at z~7-8 in the next few years. If increase in density implied in lensed LAE survey proves false, z~10 objects may be difficult to find before JWST, especially for (non-lensing) ground-based imaging surveys

25. thanks

26. Expected for young star- forming objects at z~7-8

27. A1835 F850LP F110W F160W

28. RXJ1347 F850LP F110W F160W

29. Gravitational TelescopeLensing or not lensing ? Lensing introduces two opposite trends Advantages: - boosts the total flux by increasing the observed size of background sources (constant surface brightness) - efficient for unresolved sources - multiple images configuration gives a hint on z • Drawbacks: • Effective area smaller in the source plane (compensate by observing more clusters) • Need to estimate the magnification to correct it (good lens model) What really happens What we observe

30. MS0451

31. Director’s Discretionary Time MS0451 F850LP F110W F160W

32. Lyman-Break-TechniqueLyman α =1215.67Å

33. Lyman-Break-TechniqueLyman α =1215.67Åλo=(1+z)λi

34. Gravitational TelescopeLensing or not lensing ? Lensing introduces two opposite trends Advantages: - boosts the total flux by increasing the observed size of background sources (constant surface brightness) - efficient for unresolved sources - multiple images configuration gives a hint on z • Drawbacks: • Effective area smaller in the source plane (compensate by observing more clusters) • Need to estimate the magnification to correct it (good lens model)

35. Lensing or not lensing ? UDF Blank field • light contamination coming from the large number of bright cluster galaxies, • reduces the surface area reaching the maximum depth, prevents the detection of faint objects, • especially in the vicinity of the cluster center, • this effect can be as high as 20% of the total surface (Richard et al. 2006), • it is almost negligible in blank field surveys.

36. Spectroscopic Elimination of Interlopers • For typical starburst galaxy emission line ratios, sensitivity should have been sufficient to detect lines if galaxy were at low-redshift. • No emission lines detected: candidates are probably not H, [OII], [OIII] • optical broadband • No detection • Bottom line: while spectroscopic follow-up does not show that any of candidates are at low-redshift, possibility remains that candidates are low-z with non-standard line ratios

37. Luminosity function Number density=-3.6 N/mag/Mpc^3

38. History of searching hi-z lensed galaxies • 1987: Cl2244 one of the first gravitational arc, latter recognized as a z=2.2 galaxy • Ebbelset al 1996: a z=2.5 LBG in a2218 • cB58 z=2.7 recognized as a strongly lensed source (Seitz et al 1998) • Franxet al 1997: a LAE at z=4.9 • Ellis et al 2001: LAE at z=5.6 • Kneibet al 2004, Egami et al 2005: LBG at z~6.8 • Bradley et al 2008: LBG at z~7.6