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Luminosity function and SFRs at z=6-10: Galaxy Buildup in the Reionization Epoch

This study focuses on galaxies at redshifts z~6-10 to understand their role in reionization and their rapid buildup in luminosity and mass. It also explores the unique stellar populations of galaxies at these epochs.

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Luminosity function and SFRs at z=6-10: Galaxy Buildup in the Reionization Epoch

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  1. Luminosity function and SFRs at z=6-10: Galaxy Buildup in the Reionization Epoch Rychard Bouwens & Garth Illingworth Galaxies and Structures through Cosmic Times HST ACS UDF Venice 2006 N

  2. Galaxies at Redshift z~6-10 The First Gyr of Galaxy Formation With Special Thanks to: John Blakeslee, Marijn Franx, Massimo Stiavelli, Louis Bergeron, Rodger Thompson, Ivo Labbe, Dan Magee, Daniel Eisenstein, Tom Broadhurst, Corey Dow-Hygelund ACS GTO team:Holland Ford, Garth Illingworth, Mark Clampin, George Hartig, Txitxo Benitez, John Blakeslee, Rychard Bouwens, Marijn Franx, Gerhardt Meurer, Marc Postman, Piero Rosati, Rick White, Brad Holden, Dan Magee + many other team members UDF-IR team:Rodger Thompson, Garth Illingworth, Rychard Bouwens, Mark Dickinson, Pieter van Dokkum, Dan Eisenstein, Xiaohui Fan, Marijn Franx, Marcia Rieke, Adam Riess HST:WFPC2 + NICMOS + ACS Cosmic Times - Venice 03/31/06 RJB/GDI

  3. Galaxies at Redshift z~6-10 Key Science Interests Dropout Redshift Selection Functions 1) Galaxies as possible reionization sources • -- This follows from evidence from z~6 SDSS quasars and 3-year WMAP optical depth measurements that the universe was likely reionized between z~6 and 11… 2) The luminosity and masses of galaxies at these epoches are likely to build up very rapidly. 3) Galaxies at these epochs are likely to show unique and very interesting stellar populations (new IMFs, zero metallicities, and no dust) Focusing on Galaxies at these redshifts 2006 Winter AAS Meeting 01/11/06 RJB

  4. Galaxies at z~6 (i-dropouts) Dropout Redshift Selection Functions Cosmic Times - Venice 03/31/06 RJB/GDI

  5. Galaxies at z~6 (i-dropouts): circa 2005 Wide Deep GOODS HDF-N UDF-Parallels CDF-S UDF z850,AB~ 28.4 (10) z850,AB~ 29.2 (10) 17 arcmin2 11 arcmin2 Now 506 z~6 i-dropouts! >92% are at z~6 z850,AB~ 27.1 (10) (vers: 1.0) 27.5 (vers: 1.9) 316 arcmin2 Bouwens, Illingworth, Blakeslee, Franx 2006 Cosmic Times - Venice 03/31/06 RJB/GDI

  6. Galaxies at z~6 (i-dropouts): UV Luminosity Function Rigorous i-dropout luminosity function determination • Applied a well-tested i-z > 1.3 criterion to select i-dropouts in all fields. • Used detailed degradation experiments on our deeper fields to perform completeness and flux corrections. • Carefully matched up surface densities of all fields to remove field-to-field variations (35% effect) • Accounted for blending with foreground objects (5-10% effect) • Determined contamination level (5-10% effect): • Intrinsically-red objects • Photometric scatter • Stars • Spurious sources • Selection function determined by using best estimates of UV colors and sizes of z~6 objects.

  7. Galaxies at z~6 (i-dropouts) z~6 UV Luminosity Function Log # mag-1 Mpc-3 z~6 506 (!) i-dropout galaxies M* = -20.20  = -1.74 * = 0.002 Rest frame UV 1350 Å Bouwens, Illingworth, Blakeslee, Franx 2006 Cosmic Times - Venice 03/31/06 RJB/GDI

  8. Galaxies at z~6 (i-dropouts) z~6 UV Luminosity Function LF at z~6: goes ~3 mag below L* z~3 Log # mag-1 Mpc-3 z~6 M* = -20.20  = -1.74 * = 0.002 Rest frame UV 1350 Å Bouwens, Illingworth, Blakeslee, Franx 2006 Cosmic Times - Venice 03/31/06 RJB/GDI

  9. Galaxies at z~6 (i-dropouts) z~6 UV Luminosity Function Luminosity evolution provides the best fit - not density evolution Luminosity Evolution Provides a good fit Log # mag-1 Mpc-3 M* = -20.20  = -1.74 * = 0.002 Rest frame UV 1350 Å Bouwens, Illingworth, Blakeslee, Franx 2006 Cosmic Times - Venice 03/31/06 RJB/GDI

  10. z~6 UV Luminosity Function Shallow Faint-end Slope The characteristic luminosity at z~6 (L*UV,z~6) is ~50% of (L*UV,z~3) at z~3. Steep Faint Bright Rest frame UV 1350 Å Bouwens et al 2006 Cosmic Times - Venice 03/31/06 RJB/GDI

  11. Evolution of the UV LF Bright Characteristic UV Luminosity Hierarchical Buildup AGN Feedback?Enviroment?Transition between Hot/Cold Cooling Flows? Faint Cosmic Times - Venice 03/31/06 RJB/GDI

  12. Star Formation History -- z ~ 0 - 6 Star Formation History Brighter Flux Limit Evolution in SFR density is much flatter when integrating to faint limits Luminosity Density (Star Formation Rate Density - no extinction) z~6 result Log10 Myr-1Mpc-3 Fainter Flux Limit z~6 result Bouwens et al. 2006 Cosmic Times - Venice 03/31/06 RJB/GDI

  13. Evolution in UV Continuum Slope UV continuum slope vs. z Dusty Red UV continuum slope Dust Free Blue Galaxies appear to become less dusty at high redshift Bouwens et al. 2004, 2006b,c; See also Stanway et al. 2005; Lehnert et al. 2003; Yan et al. 2005

  14. Star Formation Rate (SFR) History to z~6 Star Formation History Dust Corrected Log10 Msolyr-1 Mpc-3 Uncorrected Most Significant Dust Corrections Dust-corrected SFR shows a much more significant drop to high redshift than uncorrected. Cosmic Times - Venice 03/31/06 RJB/GDI

  15. Can the galaxies at z~6 reionize the universe? Theory dM*/dt ≈ (0.052)(C30)(0.5/fesc,rel)((1+z)/7)3 (Madau et al. 1998) C=<2>/<>2=10 fesc,rel = 0.2 (Shapley et al. 2006, in prep) dM*/dt = 0.043 (needed) Cosmic Times - Venice 03/31/06 RJB/GDI

  16. Can the galaxies at z~6 reionize the universe? Theory Observations dM*/dt ≈ (0.052)(C30)(0.5/fesc,rel)((1+z)/7)3 Use Bouwens et al. (2006) LF at z~6 (Madau et al. 1998) C=<2>/<>2=10 fesc,rel = 0.2 (Shapley et al. 2006, in prep) dM*/dt = 0.043 (needed) dM*/dt = 0.043 (observed) Cosmic Times - Venice 03/31/06 RJB/GDI

  17. Can the galaxies at z~6 reionize the universe? Theory Observations dM*/dt ≈ (0.052)(C30)(0.5/fesc,rel)((1+z)/7)3 Use Bouwens et al. (2006) LF at z~6 (Madau et al. 1998) C=<2>/<>2=10 fesc,rel = 0.2 (Shapley et al. 2006, in prep) dM*/dt = 0.043 (needed) dM*/dt = 0.043 (observed) Yes, it appears they can Cosmic Times - Venice 03/31/06 RJB/GDI

  18. Can the galaxies at z~6 reionize the universe? Theory Observations dM*/dt ≈ (0.052)(C30)(0.5/fesc,rel)((1+z)/7)3 Use Bouwens et al. (2006) LF at z~6 (Madau et al. 1998) C=<2>/<>2=10 fesc,rel = 0.2 (Shapley et al. 2006, in prep) dM*/dt = 0.043 (needed) dM*/dt = 0.043 (observed) No need for extremely steep faint-end slopes (as suggested by Yan et al. 2004), ultra low metallicities, or top heavy IMFs (as suggested by Stiavelli et al. 2004). Cosmic Times - Venice 03/31/06 RJB/GDI

  19. Galaxies at z~7 (z-dropouts) Dropout Redshift Selection Functions Cosmic Times - Venice 03/31/06 RJB/GDI

  20. Galaxies at z~7 (z-dropouts) • 5 candidate z-dropouts z ~7 galaxies selected from the UDF + UDF-IR (~6 arcmin2) Two-color dropout selection ACS NICMOS JAB ~ HAB ~27 mag • – 1±1 contaminants ~3-4 z~7 galaxies Bouwens, Thompson, Illingworth et al 2004c Cosmic Times - Venice 03/31/06 RJB/GDI

  21. Galaxies at z~7 (z-dropouts) • 5 candidate z-dropouts z ~7 galaxies selected from the UDF + UDF-IR (~6 arcmin2) Two-color dropout selection ACS NICMOS JAB ~ HAB ~27 mag • – 1±1 contaminants • – 2 electronic ghosts of stars (NICMOS artifact) ~1-2 z~7 galaxies Bouwens, Thompson, Illingworth et al 2004c Cosmic Times - Venice 03/31/06 RJB/GDI

  22. Artificial Redshifting “Cloning” Engine z~6 sample (1+z)4 cosmological surface brightness dimming z~7-8 sample Bouwens 1998a,b; Bouwens et al 2003a; Bouwens et al. 2006b

  23. Galaxies at z~7 (z-dropouts) Our cloning simulations predict: ~6 z-dropouts (assuming no-evol from z~6)  find ~2 objects Star Formation History Luminosity Density (Star Formation Rate Density - no extinction) HUDF z~7 result Log10 Msolyr-1 Mpc-3 From z~6 sample Bouwens, Thompson, Illingworth et al 2004c Cosmic Times - Venice 03/31/06 RJB/GDI

  24. Galaxies at z~7 (z-dropouts) Our cloning simulations predict: ~6 z-dropouts (assuming no-evol from z~6)  find ~2 objects Star Formation History Luminosity Density (Star Formation Rate Density - no extinction) HUDF z~7 result Log10 Msolyr-1 Mpc-3 From z~6 sample Bouwens, Thompson, Illingworth et al 2004c Cosmic Times - Venice 03/31/06 RJB/GDI

  25. Galaxies at z~10 (J-dropouts) Dropout Redshift Selection Functions Cosmic Times - Venice 03/31/06 RJB/GDI

  26. Galaxies at z~10 (J-dropouts) HDF-N Dickinson HDF-N Thompson • Performed a search for J-dropouts in all deep NICMOS J+H data from HDF-N, HDF-S, UDF, and UDF parallels (~800 HST orbits) HDF-S Parallel H~28.1 mag, 0.8 arcmin2 H~28.2 mag, 0.8 arcmin2 UDF Thompson 5, AB mags H~27.0 mag, 5.2 arcmin2 UDF Parallel #1 UDF Parallel #2 H~28.5 mag, 1.3 arcmin2 H~28.5 mag, 1.3 arcmin2 H~27.5 mag, 5.8 arcmin2 Cosmic Times - Venice 03/31/06 RJB/GDI

  27. Galaxies at z~10 (J-dropouts) • J-H>1.8 “J-dropout” criterion 11 J-dropout candidates in the 6 fields (14.7 arcmin2) • 8 of the 11 were clearly NOT high redshift objects - detected in optical bands or had quite red H-K colors. •  3 z~10 candidates (from 800 HST orbits...!) z~10 candidates Example: Low Redshift Contaminant“Dickinson HDF-N J-dropout” Bouwens, Illingworth, Thompson, Franx 2005a Cosmic Times - Venice 03/31/06 RJB/GDI

  28. Galaxies at z~10 (J-dropouts) • J-H>1.8 “J-dropout” criterion 11 J-dropout candidates in the 6 fields (14.7 arcmin2) • 8 of the 11 were clearly NOT high redshift objects - detected in optical bands or had quite red H-K colors. •  3 z~10 candidates (from 800 HST orbits...!) z~10 candidates The new data from an ACS program suggests that 2 out of the 3 candidates are not z~10 sources. Example: Low Redshift Contaminant“Dickinson HDF-N J-dropout” Bouwens, Illingworth, Thompson, Franx 2005a Cosmic Times - Venice 03/31/06 RJB/GDI

  29. Galaxies at z~10 (J-dropouts) “Cosmic Variance” due to LSS is ~19% RMS. • Our cloning simulations predict ~5 J-dropouts • (assuming no-evolution from z~6) Star Formation History Luminosity Density (Star Formation Rate Density - no extinction) Log10 Msolyr-1Mpc-3 If none of the candidates are at z~10 Bouwens, Illingworth, Thompson, Franx 2005a Cosmic Times - Venice 03/31/06 RJB/GDI

  30. Deep Optical/Infrared Fields Now, there is a growing number of search fields with deep optical and infrared data in which high redshift dropouts can be found…… HDF North GOODS CDF South GOODS z~6 UDF HDFN Ultra Deep NICMOSAB > ~ 28 (5) Deep NICMOSAB > ~ 27 (5) ~19 arcmin2 of very deep optical + IR area

  31. Galaxies at z~7 revisited (z-dropouts) Dropout Redshift Selection Functions Cosmic Times - Venice 03/31/06 RJB/GDI

  32. A few new z ~ 7 candidates z V i H J Detection No Detection Cosmic Times - Venice 03/31/06 RJB/GDI

  33. Star Formation History Luminosity Density (Star Formation Rate Density - no extinction) Log10 Myr-1Mpc-3 z~6 result While analysis is incomplete latest data suggest a more significant drop earlier than z~6 (from ~0.7-0.9 Gyr) Cosmic Times - Venice 03/31/06 RJB/GDI

  34. Star Formation History Luminosity Density (Star Formation Rate Density - no extinction) Log10 Myr-1Mpc-3 z~6 result While analysis is incomplete latest data suggest a more significant drop earlier than z~6 (from ~0.7-0.9 Gyr) Cosmic Times - Venice 03/31/06 RJB/GDI

  35. The First Gyr: Galaxies at z~6-10Conclusions Measured large sample of ~506 I-dropout galaxies from HST ACS and NICMOS data. z~6 UV LF rigorously determined to ~3 mags below L* -- fainter than any LF at high redshift (z > 2). Faint end slope similar, and could be steeper than at z~3. z~6 galaxies contribute UV flux sufficient to complete reionization Demonstrated substantial evolution at the bright end of the UV LF from z~6 to z~3 - characteristic luminosity at z~6 (L*UV) is ~50% fainter than that at z~3. HST ACS/NICMOS UDF data provided first detection of a sample of z~7 galaxies. ~3x decrease in luminosity density from z~6 to z~7. Strongest constraint yet on z~10 galaxy luminosity density Star formation rate increases only slowly from z~6 to z~3, but appears to be substantially less only 2-300 million years earlier at z~7-10 Cosmic Times - Venice 03/31/06 RJB/GDI

  36. WMAP cosmology Cloning Procedure (1+z)4 cosmological surface brightness dimming (B/V/I color images) Cosmic Times - Venice 03/31/06 RJB/GDI

  37. Cloning is a much more direct approach How to compare samples? Cloning vs Models • Cloning technique: empirical approach for comparing galaxies over a wide range of redshifts • Calibrated photometric redshifts using flux decrement at Ly-limit and Ly • Cloning technique provides a methodology for dealing with physical (cosmological), observational and instrumental effects Best representation of multi-dimensional galaxy parameter space is the sample itself Cloning Dropouts: Implications for Galaxy Evolution at High Redshift. Bouwens, Broadhurst and Illingworth, Ap. J., 593, 640, 2003; and Bouwens, Illingworth et al Ap. J., 606, 25, 2004 Cosmic Times - Venice 03/31/06 RJB/GDI

  38. Ap.J. 1998 Cosmic Baryon Budget Where baryons are at z~0: 83% are in gas/plasma 17% are in stars - of which: 73% in spheroids (bulges/Es) 25% in disks 2% in late-type galaxies Key issue at high-redshift (z>2):  identifying and characterizing spheroid (bulges and Es)  disk formation (precursor buildup?) Cosmic Times - Venice 03/31/06 RJB/GDI

  39. Large Scale Structure Arc Simulation - showing the region around a rich cluster at z~1.4 Springel et al 2005 millennium simulation Cosmic Times - Venice 03/31/06 RJB/GDI

  40. Galaxies at z~6-7+ The “dropout” technique - using the break at the Lyman limit at all redshifts and at Ly at high redshifts Ly Distant galaxy selection by the “drop-out” technique – a ‘U-dropout’ here (Dickinson 1999) Cosmic Times - Venice 03/31/06 RJB/GDI

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