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

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

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

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  1. Physical Properties of Spectroscopically Confirmed Galaxies at 5.6<z<7.3 Linhua Jiang (Arizona State University ) Hubble Fellow Symposium 2012

  2. 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) • 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 (Robertson+2011) (Robertson+2011)

  3. Physical Properties of z ≥ 6 Galaxies • SED modeling • Difficulty: UV  near-IR, optical  mid-IR • Model broad-band SEDs with HST and Spitzer • HST: UV slope  young populations • 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)

  4. 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

  5. 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.

  6. 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

  7. NICMOS + IRAC z J H IRAC1 IRAC2

  8. IRAC + WFC3 z IRAC1 IRAC2 z IRAC1 IRAC2

  9. 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.

  10. 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

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

  12. 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)

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

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

  15. Our results: a few examples LBG@z=6.11 LBG@z=5.9 LAE@z=6.6 • Mature/evolved galaxy ? • age ~ 200-400 Myr • Mstar ~ 3x1010 M • Young bursting galaxy? • age < 20 Myr • Mstar ~ 5x108 M • Strong emission line in the IRAC 3.6μm band?

  16. IOK-1: LAE at z=6.96 z N973 1.1μm 1.6μm 3.6μm 3.6μm-c

  17. IOK-1: LAE at z=6.96 • Big Balmer break  age: 100 – 200 Myr • Steep UV slope  low extinction and metal. • Stellar mass ≈ 5x109 M

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

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

  20. Morphology • Interacting/merging • ~1/3 are mergers • ~50% mergers at MUV < – 21 • Morphological parameters • CAS (Conselice 2003) • Gini and M20(Lotz+2004,2006)

  21. 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

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