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Galaxy Buildup in the First 2 Gyr: The Evolution of the UV LF from z~8 to z~4

Galaxy Buildup in the First 2 Gyr: The Evolution of the UV LF from z~8 to z~4. Rychard Bouwens (University of California, Santa Cruz) Garth Illingworth. August 29, 2007 Venice, Italy Century of Cosmology: Past, Present, Future. N. HST UDF. Galaxy Buildup in the First 2 Gyr.

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Galaxy Buildup in the First 2 Gyr: The Evolution of the UV LF from z~8 to z~4

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  1. Galaxy Buildup in the First 2 Gyr: The Evolution of the UV LF from z~8 to z~4 Rychard Bouwens (University of California, Santa Cruz) Garth Illingworth August 29, 2007Venice, ItalyCentury of Cosmology: Past, Present, Future N HST UDF

  2. Galaxy Buildup in the First 2 Gyr With a Special Thanks to: Marijn Franx, John Blakeslee, Holland Ford, Rodger Thompson, Louis E. Bergeron, Massimo Stiavelli, Dan Magee, Ivo Labbe, Pieter van Dokkum, Dan Coe, Larry Bradley 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:NICMOS + ACS

  3. Galaxy Buildup in the First 2 Gyr 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 2007 Venice 08/29/07 RJB

  4. Other Work on z>3 UV LFs Elizabeth Stanway Andy Bunker Some of the first z~6 work, found a significant drop at bright end of z~6 LF Haojing Yan Faint-end slope of the z~6 LF was likely steep Presented evidence that the evolution of the UV luminosity density was very mild from z~6 to z~3 Mauro Giavalisco Presented some preliminary evidence that the characteristic luminosity of z~6 galaxies may have been fainter than at z~3 Mark Dickinson Makiko Yoshida Found evolution in the characteristic luminosity from z~5 to z~4 Noted a significant deficit in the number of bright galaxies at z~6 Kazuhiro Shimasaku Performed first LF determinastion at z~4-5 using deep HUDF data Steve Beckwith Massimo Stiavelli z>6 searches on UDF05 Fields Naveen Reddy, Chuck Steidel, Marcin Sawicki, Ikiru Iwata, Olivier Le Fevre, Laurence Tresse, Stephane Paltani, Filippo Mannucci, Oesch

  5. Galaxies at z~4, 5, & 6 (B, V, i-dropouts) Dropout Redshift Selection Functions

  6. Galaxies at z~4, 5, 6 Wide Deep GOODS “v2.0” UDF HDF-N CDF-S z850,AB~ 29.3 (5) 11 arcmin2 UDF UDF-Parallels z850,AB~ 28 (5) z850,AB~ 28.8 (5) 320 arcmin2 40 arcmin2 4671 z~4 B-dropouts, 1416 z~5 V-dropouts, 627 z~6 i-dropouts! Bouwens, Illingworth, Blakeslee, Franx et al 2006 Bouwens, Illingworth et al. 2007 (see also work by Beckwith et al. 2006; Giavalisco et al.)

  7. Same faint-end slope  ~ -1.75 MILD EVOLUTION Galaxies at z~4, 5, 6 (B, V, i-dropouts) UV Luminosity Functions Large range in M1600: -16 to -22.5! z~4 Log # mag-1 Mpc-3 z~6 UV LF (Bouwens et al. 2006)  Rest frame UV 1600 Å M* Bouwens, Illingworth, Franx, and Ford 2007

  8. Galaxies at z~4, 5, 6 (B, V, i-dropouts) UV Luminosity Functions Shallow z~6 z~5 z~4 Faint-end slope  Faint end slope is constant  ~ 1.75 Steep  Bright M* Faint M* Bouwens, Illingworth, Franx, and Ford 2007

  9. Downsizing Hierarchical Buildup AGN Feedback? Evolution of the UV Luminosity Function Bright M*UV Faint Redshift Bouwens, Illingworth, Franx, & Ford 2007 Venice 08/29/07 RJB

  10. Galaxies at z~7-8 (z-dropouts) Dropout Redshift Selection Functions

  11. Deep NICMOS Imaging Around Lensing Clusters ISAAC Galaxies at z~7-8 (z-dropouts) Many fields with deep ACS and NICMOS data for dropout searches Deep NICMOS area (orange and red regions) will soon cover~80 arcmin2 ACS NICMOS JAB ~ HAB >= 26.5 mag

  12. Bouwens et al. 2007 z ~ 7-8 Galaxies Criteria: z-J > 0.8, J-H < 1.2 No Detection in deep B, V, i data Remove T-dwarfs (2 identified and excluded from the sample) Examine IRAC / MIPS data to exclude lower redshift sources 9 good z-dropout candidates

  13. Are we really finding z>7 galaxies? • 5 detections in J, H, IRAC 3.6 channel, and 2.5  in IRAC 4.5  channel • Very Blue J - H colors • Undetected in the HUDF B, V, i, and z band imaging • (z-J) > 3 -- too red to be a brown dwarf • (H - 3.6) colors similar to z~6 objects Labbe, Bouwens, Illingworth, Franx 2006 Venice 08/29/07 RJB

  14. Are we really finding z>7 galaxies? • 8 detections in J, H, IRAC 3.6 channel, and 2.5  in IRAC 4.5  channel • Very Blue J - H colors • Extremely red z-J > 2.5 colour • Undetected in very deep V, i, z band imaging, even in stacked exposures • Extended so cannot be a brown dwarf • (H - 3.6) colors similar to z~6 objects Venice 08/29/07 RJB

  15. Galaxies at z~4, 5, 6, 7.5 (B, V, i, z-dropouts) UV Luminosity Functions z~4 z~6 Log # mag-1 Mpc-3 Faint Bright M* Bouwens et al. 2007 Heidelberg 07/18/07 RJB

  16. z~7.5 Galaxies at z~4, 5, 6, 7.5 (B, V, i, z-dropouts) UV Luminosity Functions z~4 z~6 Log # mag-1 Mpc-3 Faint Bright M* Bouwens et al. 2007 Heidelberg 07/18/07 RJB

  17. z~7.5 Galaxies at z~4, 5, 6, 7.5 (B, V, i, z-dropouts) UV Luminosity Functions High z~6 z~5 z~4 Volume Density * ~ 0.0013 Mpc–3 at z~4, 5, 6, 7.5 * z~7-8 contours fit in nicely with z~4-6 trends! Suggests we are actually finding z~7-8 galaxies! Low  Bright M* Faint M* Bouwens et al. 2007 Venice 08/29/07 RJB

  18. Downsizing Hierarchical Buildup AGN Feedback? Evolution of the UV Luminosity Function Bright M*UV Faint Redshift Bouwens, Illingworth, Franx, & Ford 2007 Venice 08/29/07 RJB

  19. Downsizing Hierarchical Buildup AGN Feedback? Evolution of the UV Luminosity Function Bright M*UV Faint Redshift Bouwens, Illingworth et al. 2007 Venice 08/29/07 RJB

  20. Galaxies at z~10 (J-dropouts) Dropout Redshift Selection Functions Heidelberg 07/18/07 RJB

  21. Search for z~10 J-dropouts: Criteria: J-H > 1.3, H - K < 1.5 (where available) H - 3.6 µm < 2.5 • => 0 z~10 candidates Galaxies at z~10 (J-dropouts) Many fields with deep ACS and NICMOS data for dropout searches Deep NICMOS area (orange and red regions) will soon cover~80 arcmin2 ACS NICMOS JAB ~ HAB >= 26.5 mag Venice 08/29/07 RJB

  22. Downsizing Hierarchical Buildup AGN Feedback? Evolution of the UV Luminosity Function Bright M*UV Faint Redshift Bouwens, Illingworth et al. 2007 Venice 08/29/07 RJB

  23. Evolution of the UV Luminosity Function Downsizing Bright Hierarchical Buildup M*UV AGN Feedback? Faint Redshift Assuming phi* ~ 0.0013 Mpc-3 at z~10 (i.e., no evolution) Bouwens, Illingworth et al. 2007 Venice 08/29/07 RJB

  24. Mass Function Surprisingly, the evolution we observe in M*(UV) is almost identical to what we would expect from the evolution of the halo mass function and assuming no evolution in the M/L ratio! Sheth & Tormen 1999 Evolution of the UV Luminosity Function Downsizing Bright M*UV Mass Func Evolution Faint Redshift Bouwens, Illingworth et al. 2007 Venice 08/29/07 RJB

  25. Evolution of the UV Luminosity Function Gravity + Hydro Model Results Downsizing Bright M*UV Mass Func Evolution Faint Momentum conserving wind model Oppenheimer & Dave 2006 Redshift Bouwens, Illingworth et al. 2007 Venice 08/29/07 RJB

  26. UV Luminosity Density & SFR History Luminosity Density: Log ergs s-1 Hz-1 Mpc-3 SFR: Log10 Myr-1Mpc-3 “Cosmic Variance” due to large scale structure: at z~4-6 ~14% RMS at z~7-8 ~25% RMS at z~10 ~19% RMS Upper limit from z~10 search Bouwens et al. 2007 Venice 08/29/07 RJB

  27. Spitzer Observations of z~7 Galaxies

  28. Stellar Masses of z~7 Galaxies Rest-frame optical fluxes from Spitzer IRAC Rest-frame UV Rest-frame Optical Stellar Masses of 0.3 - 1.0 x 1010 M Ages of ~50-200 Myr Stellar Mass Density at z~7.4 (> 0.3 L*) is 20-60% of z~5-6 values Labbe, Bouwens, Illingworth, Franx, Ap.J., 2006

  29. Mass Buildup from z~7 • Stellar Mass Density • vs Redshift • From z~7 (0.7Gyr) to present day Labbe, Bouwens, Illingworth, Franx, Ap.J., 2006

  30. New Measurements of the UV LFs at z>6: Conclusions UDF and GOODS ACS and NICMOS data are superb for z~4 to z~7-10 dropout searches ~4700 B-dropouts (z~4), ~1400 V-dropouts (z~5) and ~600 i-dropouts (z~6) are found in deep HST ACS data z~4,5,6 UV Luminosity Function determined to 3-5 mags below L* Soon >=80 arcmin2 of deep (>=26.5 AB mag) near-IR data will be available over areas with deep optical coverage Using these data, we have identified 9 z~7-8 z-dropout candidates, with luminosities ranging from 0.1 L*(z=3) to 1.0 L*(z=3) The characteristic luminosity of galaxies in the UV appears to brighten substantially (by ~1.2 mag) from z~7.5 to z~3. The increase in the characteristic luminosity M* is almost identical to that expected for the halo mass function -- suggesting that the observed evolution can be explained with hierarchical buildup We have detected likely z~7-8 galaxies with Spitzer IRAC in the rest-frame optical and estimated stellar masses of ~5 x 109 solar masses Venice 08/29/07 RJB

  31. However, new data from a very deep ACS program and improved NICMOS reductions has suggested that none of the 3 candidates at z~10 ACS NICMOS Credit: Stiavelli V i z J H Previous J-dropout Search • J-H>1.8 “J-dropout” criterion -- excluding sources with • optical detections, very red H-K colours, or very H-3.6µm colours •  3 z~10 candidates (from 800 HST orbits...!) z~10 candidates Example: Low Redshift Contaminant excluded using IRAC data“Dickinson HDF-N J-dropout” Bouwens, Illingworth, Thompson, Franx 2005a Venice 08/29/07 RJB

  32. How easy is it to select galaxies at z~7-8? What is the selection volume? Artificial Redshifting “Cloning” Engine z~4 sample (1+z)4 cosmological surface brightness dimming z~7-8 sample Bouwens 1998a,b; Bouwens et al 2003a; Bouwens et al. 2006b

  33. Expected UV colours of z>6 Galaxies 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

  34. 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

  35. Expected Sizes ofz>6 Galaxies Observed Sizes vs. Redshift Sizes Bouwens et al. (2004) The sizes of i-dropouts are in good agreement with size-redshift trends found in Ferguson et al. (2004) Venice 08/29/07 RJB

  36. Lyman Break Diagram for z-dropouts(z~7-8 galaxies) Strong Break Lyman Break Color z~7-8 No Break 4 z>6.5 candidates Blue Red Continuum Color Bouwens & Illingworth, Nature, 2006 (in press)

  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 Durham 06: Cosmic Frontiers GDI 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 Open Questions in Cosmology 08/25/05 GDI

  38. “Dropout” Galaxies The “dropout” technique - using the break at the Lyman limit and at Ly at high redshifts Ly Distant galaxy selection by the “drop-out” technique – a ‘U-dropout’ here (Dickinson 1999) Open Questions in Cosmology 08/25/05 GDI

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