Epoch of Reionization  Cosmic Reionization: Neutral IGM ionized by the first luminous objects at 6 < z < 15 Evidence: CMB polarization (Komatsu+2009) + GP troughs (Fan+2006) + … Responsible sources for Reionization? (e.g. Finlator+2011)  High-z galaxies (z ≥ 6): HST + the largest ground-based telescopes A few hundred galaxies or candidates at z ≥ 6; many at z ≥ 7 (e.g. Oesch+2010; Bouwens+2011; Stark+2011; Yan+2011; and many others) Physical properties (e.g. Gonzalez+2010; Finkelstein+2011; McLure+2011) (Robertson+2011)

 SED modeling Difficulty: UV  near-IR, optical  mid-IR Model broad-band SEDs with HST and Spitzer a)HST: UV slope  young populations b)Spitzer: Balmer break  mature populations  Current issues: LBGs found by HST are very faint  no spec-z, probably no IRAC detections LBGs or LAEs found by ground-based telescopes are bright, but  usually do not have HST or Spitzer data (Egami+2005) Physical Properties of z ≥ 6 Galaxies

 Solution – bright, spec-confirmed galaxies: Subaru Deep Field: largest sample of spec-confirmed galaxies at z ≥ 6 Redshifts: remove one critical free parameter for SED modeling Brightness: ensure high-quality imaging data Bias: toward the most luminous galaxies  Outline: Subaru Deep Field (SDF) and its data Rest-frame UV and physical properties from HST and Spitzer Morphology This is the first systematic study of spec.-confirmed galaxies at z ≥ 6

Subaru Deep Field (SDF)  Spec. confirmed galaxies: > 50 LAEs at z ≈ 5.7 > 40 LAEs at z ≈ 6.5 > 30 LBGs at 6 < z < 6.5 1~2 LAE at z ≈ 7 1~2 LAEs at z ≈ 7.3  Optical imaging data: Area: > 800 arcmin 2 Broad-band data: BVRi≈28.5, z≈27.5, y≈26.5 (AB at 3σ); PSF≈0.6” Narrow-band data: NB816, NB921, NB973, etc.

Our plan  HST: F125W (F110W) and F160W Coverage: ~60 galaxies Current depth: 1 orbit (PIs Jiang and Egami) Final depth: 2 orbits (PI Jiang)  Spitzer: IRAC 1 and 2 Coverage > 60% of SDF Current depth: 3 hrs (PIs Jiang and Egami) Final depth: 6 hrs (PI Jiang)  Current sample: ~30 galaxies

NICMOS + IRAC z J H IRAC1 IRAC2

IRAC + WFC3 z IRAC1 IRAC2 z IRAC1 IRAC2

 Photo. and Spec. measurements Galaxy model: Lyα line + power-law continuum + IGM absorption Data: all photometric data from i to H Results: Lyα strength + UV continuum and slope  M UV, EW, SFR, etc.

UV slope and Lyα EW  Rest-frame UV slope –1<β<–4; median –2.4 Fainter  steeper Faintest half sample: β ~ –3 LAEs have steeper β than LBGs  Rest-frame Lyα EW EW-luminosity relation

Lyα luminosities Photometric measurements vs. spectroscopic measurements (Jiang+2011)

(Kashikawa+2011) Lyα luminosity function (LF) Strong evolution of the LAE LF from z ≈ 5.7 to 6.5  Increasing neutral fraction of IGM ? UV LFLyα LF

(Kashikawa+2011) Lyα luminosity function (LF) Strong evolution of the LAE LF from z ≈ 5.7 to 6.5  Increasing neutral fraction of IGM ? UV LFLyα LF Corrected

 SED modeling Difficulty: UV  near-IR, optical  mid-IR Model broad-band SEDs with HST and Spitzer a)HST: UV slope  young populations b)Spitzer: Balmer break  mature populations (Egami+2005) Physical Properties of z ≥ 6 Galaxies (LBGs at z ≈ 7; Gonzalez+2010) (LBGs at z ≈ 6; Eyles+2007) (LAEs at z ≈ 5; Pirzkal+2007)

 Mature/evolved galaxy ? age ~ Myr Mstar ~ 3x10 10 M   Strong emission line in the IRAC 3.6μm band?  Young bursting galaxy? age < 20 Myr Mstar ~ 5x10 8 M  Our results: a few examples

IOK-1: LAE at z=6.96 z N μm 1.6μm 3.6μm 3.6μm-c

Big Balmer break  age: 100 – 200 Myr Steep UV slope  low extinction and metal. Stellar mass ≈ 5x10 9 M  IOK-1: LAE at z=6.96

Morphology z ≥ 7 (Oesch+2010) Galaxies at z ≥ 6 are generally compact; extended features are rare Our galaxies are the brighter and larger 1 kpc

F110W F125W image model residual z=6.96 LAE HST/WFC3 F110w/F125W

Morphology  Interacting/merging ~1/3 are mergers ~50% mergers at M UV < – 21  Morphological parameters CAS (Conselice 2003) Gini and M 20 (Lotz+2004,2006)

Summary  SDF is a good field to study high-redshift galaxies  HST and Spitzer data  characterize 60 galaxies in SDF  Current results: blue UV slopes, a range of SEDs, etc.  Morphology: a range of morphologies, many merging systems, etc.  Future data: HST 1  2 orbits; Spitzer 3  6 hours; Sample: 30  60  To do: LAEs vs. LBGs, etc.  HF symposium 2013: Quasars at z > 6.5