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Eiichi Egami Steward Observatory University of Arizona

Probing 5.7<z<7 Galaxies in the Subaru Deep Field & Lensing Cluster Surveys (including a Subaru/MOIRCS program). Eiichi Egami Steward Observatory University of Arizona. Scientific context: Reionization. z>6 QSOs showing GP troughs  z(reionize)>6

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Eiichi Egami Steward Observatory University of Arizona

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  1. Probing 5.7<z<7 Galaxies in the Subaru Deep Field& Lensing Cluster Surveys(including a Subaru/MOIRCS program) Eiichi Egami Steward Observatory University of Arizona

  2. Scientific context: Reionization • z>6 QSOs showing GP troughs  z(reionize)>6 • WMAP polarization data z(reionize)~10 • QSO’s (i.e., AGNs) considered not enough to reionize the universe • Expectation:There must be a substantial population of star-forming galaxies at z>6 that reionize the Universe.

  3. Probing z>6 Galaxies • Many galaxies already identified at z>6 with the dropout and Ly-alpha techniques. • These bright galaxies are probably not enough to reionize the Universe, but they are the only galaxes we can study in detail. HST/NICMOS & Spitzer/IRAC photometry • Fainter low-mass galaxies may be numerous and responsible for the cosmic reionization. Lensing cluster surveys

  4. 1. Probing 5.7<z<7 Galaxies in the Subaru Deep Field • IRAC on Spitzer (D=85cm telescope!) has enabled us to study the rest-frame optical SEDs of z>6 galaxies. • 3.6/4.5um bands are longward of the rest-frame Balmer/4000 A break at z<8 • Some z>6 galaxies seem fairly matureand massive (age ~ 200-300 Myr, ~109-1010M) • However, the majority seems young and less massive (age < 50-100 Myr, ~108~109M)

  5. Mature galaxies at z>6! Egami et al. 2005 Eyles et al. 2005 Yan et al. 2005

  6. BUT, there are also many young lower-mass galaxies z~6, i dropouts < 40 Myr, ~109M z=4.0-5.7, LAEs 2-3 Myr, 106-108 M Pirzkal et al. 2007 Yan et al. 2006

  7. Limitations of the Past Studies • Targets were selected in deep but small-field surveys (e.g., UDF, GOODS) • Sources are faint (especially for IRAC!)  Uncertainty with photometry, phot-z, SED modeling, etc. • Spectroscopic redshifts not available in most cases • Deep near-IR coverage limited

  8. Importance of Near-IR Data Lai et al. (2007) Near-IR data are required to break SED model degeneracy (e.g., young dusty population vs old dust-free population)

  9. Our Strategy • Target bright (z< 26 AB mag = 0.14 uJy) galaxies with spectroscopic redshifts at 5.7<z<7 -> Subaru Deep Field (SDF) • Use HST/NICMOS (1.1/1.6 um) and Spitzer/IRAC (3.6/4.5 um) to obtain SEDs. • Go after source by source instead of mapping a sky area uniformly. • Ly-alpha properties and continuum properties can be compared. • Drawback: the sample is biased toward the most luminous galaxies

  10. Team • E. Egami (Arizona; PI) • N. Kashikawa (NAOJ) • K. Shimasaku (Univ. of Tokyo) • M. Ouchi (Carnegie Obs) • R. Ellis (Caltech/Oxford) • J. Richard (Caltech) • D. Stark (Caltech) • J.-P. Kneib (OAMP) • J. Huang (CfA) • R. Dave (Arizona) • K. Finlater (Arizona) Subaru SDF Lensing cluster survey IRAC team Simulations

  11. Subaru Deep Field (SDF) • Deep Suprime-Cam broad/narrow-band imaging over ~30’x30’ (Kashikawa et al. 2004): • z~7 LAE survey (Iye et al. 2006) • z~6.5 LAE survey (Kodaira et al. 2003; Taniguchi et al. 2005; Kashikawa et al.2006) • z~6 LBG survey (Nagao et al. 2004, 2005, 2007; Ota 2008) • z~5.7 LAE survey (Shimasaku et al. 2006)

  12. Target list • 20 targets with spec-z’s • HST/NICMOS, 72 orbits, F110W/F160W, NIC3, • 1-2 orbits per source, 20 pointings • Spitzer/IRAC, 102 hrs, 3.6/4.5/5.8/8.0um • 3 hrs/band, 15 pointings

  13. LAE at z=6.55 Kashikawa et al. (2006)

  14. LAE at z=6.55 - SED • Bruzual-Charlot 2003 models • Salpeter IMF (0.1-100 M) • Age 300-400 Myr (> 200 Myr) • z_form ~ 10 • Mass 3-4x1010 M • Mature massive galaxy with little extinction

  15. i’-dropout at z=6.11 Nagao et al. (2007)

  16. i’-dropout at z=6.11 - SED • Age 200-300 Myr (> 100 Myr) • Mass ~ 7x109 M • Mature galaxy with little extiction (less massive than the previous one)

  17. LAE at z=6.54 Taniguchi et al. (2005)

  18. Very small age not likely, SFR too large LAE at z=6.54 -SED Age ~ 1 Myr Age ~ 10-100 Myr In almost all cases, sub-solar metallicity seems required to reproduce the UV slope.

  19. Status & Next steps • ~1/3 done so far • 8 sources observed with NICMOS • 7 sources observed with IRAC • BUT, only 4 sources common…. • Remaining HST imaging (12 sources) will be done with WFC3 • One more Spitzer visibility window during the cold mission -> if the program cannot be completed, we will try the warm mission. • Photometric samples will also be studied.

  20. 2. Lensing Cluster Surveys • Massive clusters of galaxies act as powerful gravitational lenses to amplify background high-redshift galaxies • x20 magnification  x20 gain in S/N  x400 gain in integration time • Strongly magnified sources located at r<1-2’  good match for ground MOS follow-up observations (e.g., LUCIFER, MODS)

  21. Lensed Lya Emitter at z=5.6 Ellis et al. (2001) Magnification factor x30 Critical-line survey

  22.  Egami et al. (2005)  z~6.5 galaxy in Abell 2218 Kneib et al. (2004) Magnification x25 z~7.6 galaxy in Abell 1689 Bradley et al. (2008)  Magnification x9.3

  23. Past/Current/Future Programs • Keck/LRIS survey (Santos et al. 2004) • Keck/NIRSPEC survey (Stark et al. 2007) • HST/NICMOS survey (Richard et al. 2008) • HST/WFC3 survey (PI: Kneib, Cycle-17, 43orbits) • Subaru/MOIRCS survey (PI: Egami, on-going) • VLT/Sinfoni survey (PI: Kneib, on-going) • Spitzer IRAC/MIPS survey (PI: Egami, on-going) • Herschel survey (PI: Egami, key program, 292hr) Emphasis on z=1-4 IR-luminous galaxies Provide useful secondary targets for MOS observations If lucky, these programs may detect some z>4 galaxies

  24. Richard et al. (2008) z~7-8 candidates (also z~10 candidates) Stark et al. (2007) 8.5<z<10.4 candidates

  25. Gravitational Lensing Power of Massive Galaxy Clusters Triply lensed ULIRG at z~2.5 seen in A2218 (Kneib et al.) Clusters transparent in the IR/submm

  26. Herschel Simulated Images of massive cluster cores (HLS) 7’x7’ Squares - m>5 PACS 100um Without lensing With lensing Clusters act as transparent lens SPIRE 250um

  27. Herschel getting ready for launch! ~ 1 billion euro telescope right there! Photo taken on July 2, 2008

  28. Subaru/MOIRCS survey (We had a very good run in May 2008, but…) 0.8” slit R~2000 VPH grism

  29. Summary • 5.7<z<7 galaxies are now routinely detected with the dropout and Ly-alpha techniques. • SEDs of some z>6 galaxies clearly suggest an earlier epoch (e.g., z~10) of vigorous star formation. • Over the next years, the frontier will shift to z>7. (i.e., near-IR narrow-band surveys, WFC3 dropout surveys) • Lensing cluster surveys may identify the faint low-mass galaxy population responsible for the cosmic reionization before JWST. • LBT/LUCIFER, MODS offer the opportunity to follow up lensed sources efficiently.

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