Physical Properties of Spectroscopically Confirmed Galaxies at 5.6<z<7.3

Linhua Jiang(Arizona State University )

Hubble Fellow Symposium 2012

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)

(Robertson+2011)

• Steven F.: galaxies at 4 < z < 8

• Kristian F.: theory, during the reionization epoch

Later this morning:

• Pascal O.: galaxies at 7 < z < 10

• Dan S.: Spectroscopic obs. of high-z galaxies

SED modeling• Difficulty: UV near-IR, optical mid-IR• Model broad-band SEDs with HST and Spitzer

a) HST: UV slope young populationsb) 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

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

Note:• LAEs: found by the NB technique

• LBGs: found by the dropout

technique

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 arcmin2

• 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 MUV, 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 luminositiesPhotometric 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 LF Lyα 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 LF Lyα LF

Corrected

SED modeling• Difficulty: UV near-IR, optical mid-IR• Model broad-band SEDs with HST and Spitzer

a) HST: UV slope young populationsb) 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 ~ 200-400 Myr • Mstar ~ 3x1010 M

Strong emission line in the IRAC 3.6μm band?

Young bursting galaxy?• age < 20 Myr• Mstar ~ 5x108 M

LAE@z=6.6 LBG@z=6.11 LBG@z=5.9

Our results: a few examples

IOK-1: LAE at z=6.96

z N973 1.1μm 1.6μm 3.6μm 3.6μm-c

• Big Balmer break age: 100 – 200 Myr• Steep UV slope low extinction and metal.• Stellar mass ≈ 5x109 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/WFC3F110w/F125W

Morphology Interacting/merging

• ~1/3 are mergers• ~50% mergers at MUV < – 21

Morphological parameters• CAS (Conselice 2003)• Gini and M20 (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 36 hours; Sample: 3060 To do: LAEs vs. LBGs, etc.

HF symposium 2013: Quasars at z > 6.5