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

Galaxies at Redshift z~6-10 HST: WFPC2 + NICMOS + ACS The First Gyr of Galaxy Formation Cosmic Times - Venice 03/31/06 RJB/GDI 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 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 UDF-IR team: Rodger Thompson, Garth Illingworth, Rychard Bouwens, Mark Dickinson, Pieter van Dokkum, Dan Eisenstein, Xiaohui Fan, Marijn Franx, Marcia Rieke, Adam Riess

Galaxies at Redshift z~6-10 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) Dropout Redshift Selection Functions Key Science Interests 2006 Winter AAS Meeting 01/11/06 RJB Focusing on Galaxies at these redshifts

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

Galaxies at z~6 (i-dropouts): circa 2005 Bouwens, Illingworth, Blakeslee, Franx 2006 Wide Deep z 850,AB ~ 27.1 (10  ) (vers: 1.0) UDF-Parallels UDF z 850,AB ~ 28.4 (10  ) z 850,AB ~ 29.2 (10  ) Now 506 z~6 i-dropouts! 17 arcmin 2 11 arcmin arcmin 2 GOODS CDF-S HDF-N >92% are at z~6 Cosmic Times - Venice 03/31/06 RJB/GDI 27.5 (vers: 1.9)

Galaxies at z~6 (i-dropouts): UV Luminosity Function  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. Rigorous i-dropout luminosity function determination

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

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

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

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

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

Star Formation History Luminosity Density (Star Formation Rate Density - no extinction) Log 10 M  yr -1 Mpc -3 Star Formation History -- z ~ z~6 result Brighter Flux Limit Fainter Flux Limit Evolution in SFR density is much flatter when integrating to faint limits Bouwens et al Cosmic Times - Venice 03/31/06 RJB/GDI

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

Star Formation History Star Formation Rate (SFR) History to z~6 Dust Corrected Uncorrected Log 10 M sol yr -1 Mpc -3 Dust-corrected SFR shows a much more significant drop to high redshift than uncorrected. Cosmic Times - Venice 03/31/06 RJB/GDI Most Significant Dust Corrections

Can the galaxies at z~6 reionize the universe? C= / 2 =10 Cosmic Times - Venice 03/31/06 RJB/GDI f esc,rel = 0.2 (Shapley et al. 2006, in prep) dM*/dt = (needed) Theory dM*/dt ≈ (0.052)(C 30 )(0.5/f esc,rel )((1+z)/7) 3 (Madau et al. 1998)

C= / 2 =10 Cosmic Times - Venice 03/31/06 RJB/GDI f esc,rel = 0.2 (Shapley et al. 2006, in prep) Use Bouwens et al. (2006) LF at z~6 dM*/dt = (needed) TheoryObservations dM*/dt = (observed) dM*/dt ≈ (0.052)(C 30 )(0.5/f esc,rel )((1+z)/7) 3 (Madau et al. 1998) Can the galaxies at z~6 reionize the universe?

C= / 2 =10 Cosmic Times - Venice 03/31/06 RJB/GDI f esc,rel = 0.2 (Shapley et al. 2006, in prep) Yes, it appears they can Use Bouwens et al. (2006) LF at z~6 dM*/dt = (needed) TheoryObservations dM*/dt = (observed) dM*/dt ≈ (0.052)(C 30 )(0.5/f esc,rel )((1+z)/7) 3 (Madau et al. 1998) Can the galaxies at z~6 reionize the universe?

C= / 2 =10 Cosmic Times - Venice 03/31/06 RJB/GDI f esc,rel = 0.2 (Shapley et al. 2006, in prep) 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). Use Bouwens et al. (2006) LF at z~6 dM*/dt = (needed) TheoryObservations dM*/dt = (observed) dM*/dt ≈ (0.052)(C 30 )(0.5/f esc,rel )((1+z)/7) 3 (Madau et al. 1998) Can the galaxies at z~6 reionize the universe?

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

Galaxies at z~7 (z-dropouts) ● 5 candidate z-dropouts Two-color dropout selection Bouwens, Thompson, Illingworth et al 2004c ● – 1±1 contaminants ~3-4 z~7 galaxies ACS NICMOS J AB ~ H AB ~27 mag z ~7 galaxies selected from the UDF + UDF-IR ( ~6 arcmin 2 ) Cosmic Times - Venice 03/31/06 RJB/GDI

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

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

Star Formation History From z~6 sample Log 10 M sol yr -1 Mpc -3 Our cloning simulations predict: ~6 z-dropouts (assuming no-evol from z~6)  find ~2 objects Galaxies at z~7 (z-dropouts) HUDF z~7 result Bouwens, Thompson, Illingworth et al 2004c Luminosity Density (Star Formation Rate Density - no extinction) Cosmic Times - Venice 03/31/06 RJB/GDI

Star Formation History From z~6 sample Log 10 M sol yr -1 Mpc -3 Our cloning simulations predict: ~6 z-dropouts (assuming no-evol from z~6)  find ~2 objects Galaxies at z~7 (z-dropouts) HUDF z~7 result Bouwens, Thompson, Illingworth et al 2004c Luminosity Density (Star Formation Rate Density - no extinction) Cosmic Times - Venice 03/31/06 RJB/GDI

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

Galaxies at z~10 (J-dropouts) ●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) UDF Thompson HDF-N Dickinson HDF-N Thompson HDF-S Parallel H~28.1 mag, 0.8 arcmin 2 H~27.0 mag, 5.2 arcmin 2 H~28.2 mag, 0.8 arcmin 2 H~27.5 mag, 5.8 arcmin 2 UDF Parallel #1 UDF Parallel #2 H~28.5 mag, 1.3 arcmin 2 5 , AB mags Cosmic Times - Venice 03/31/06 RJB/GDI

Galaxies at z~10 (J-dropouts) ●J-H>1.8 “J-dropout” criterion  11 J-dropout candidates in the 6 fields (14.7 arcmin 2 ) ●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

Galaxies at z~10 (J-dropouts) ●J-H>1.8 “J-dropout” criterion  11 J-dropout candidates in the 6 fields (14.7 arcmin 2 ) ●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 The new data from an ACS program suggests that 2 out of the 3 candidates are not z~10 sources.

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

Deep Optical/Infrared Fields z~6 CDF South GOODS HDF North GOODS UDF HDFN Ultra Deep NICMOS AB > ~ 28 (5  ) Deep NICMOS AB > ~ 27 (5  ) Now, there is a growing number of search fields with deep optical and infrared data in which high redshift dropouts can be found…… ~19 arcmin 2 of very deep optical + IR area

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

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

Luminosity Density (Star Formation Rate Density - no extinction) Log 10 M  yr -1 Mpc -3 z~6 result Star Formation History While analysis is incomplete latest data suggest a more significant drop earlier than z~6 (from ~ Gyr) Cosmic Times - Venice 03/31/06 RJB/GDI

Luminosity Density (Star Formation Rate Density - no extinction) Log 10 M  yr -1 Mpc -3 z~6 result Star Formation History While analysis is incomplete latest data suggest a more significant drop earlier than z~6 (from ~ Gyr) Cosmic Times - Venice 03/31/06 RJB/GDI

The First Gyr: Galaxies at z~6-10 Conclusions 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 million years earlier at z~7-10 Cosmic Times - Venice 03/31/06 RJB/GDI

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

How to compare samples? Cloning vs Models ● Cloning is a much more direct approach Best representation of multi-dimensional galaxy parameter space is the sample itself 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 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

Ap.J 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

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

Distant galaxy selection by the “drop- out” technique – a ‘U- dropout’ here (Dickinson 1999) 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  Cosmic Times - Venice 03/31/06 RJB/GDI