N HST ACS UDF Rychard Bouwens & Garth Illingworth Galaxies and Structures through Cosmic Times...

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 FunctionsKey Science Interests

2006 Winter AAS Meeting 01/11/06 RJB

Focusing on Galaxiesat these redshifts

Galaxies at z~6 (i-dropouts)

Dropout Redshift Selection Functions


Galaxies at z~6 (i-dropouts): circa 2005

Bouwens, Illingworth, Blakeslee, Franx 2006

Wide Deep

z850,AB~ 27.1 (10) (vers: 1.0)

UDF-ParallelsUDF

z850,AB~ 28.4 (10)z850,AB~ 29.2 (10)

Now 506 z~6 i-dropouts!

17 arcmin2

11 arcmin2

316 arcmin2

GOODS

CDF-S

HDF-N

>92% are at z~6


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


z~6

M* = -20.20 = -1.74* = 0.002

Log # mag-1 Mpc-3



LF at z~6: goes ~3 mag below L*

Log # mag-1 Mpc-3

M* = -20.20 = -1.74* = 0.002

z~3

z~6




Luminosity evolutionprovides the best fit - not density evolution

Bouwens, Illingworth, Blakeslee, Franx 2006Cosmic Times - Venice 03/31/06 RJB/GDI

Log # mag-1 Mpc-3


Luminosity Evolution Provides a good fit


M* = -20.20 = -1.74* = 0.002

z~6 UV Luminosity Function

Bouwens et al 2006 Rest frame UV 1350 Å

Faint-endSlope

The characteristic luminosity at z~6 (L*UV,z~6) is ~50% of (L*UV,z~3) at z~3.Faint Bright

Shallow

Steep


Evolution of the UV LF

Hierarchical BuildupAGN Feedback?

Enviroment?Transition between Hot/Cold Cooling

Flows?

Bright

Faint

Characteristic UV Luminosity


Star Formation History

Luminosity Density (Star Formation Rate

Density - no extinction)

Log10

M yr-1Mpc-3

Star Formation History -- z ~ 0 - 6

z~6 result

z~6 result

Brighter FluxLimit

Fainter FluxLimit

Evolution in SFR density is much flatter

when integrating to faint limits

Bouwens et al. 2006 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. 2005

Red

UV continuum slope

Blue

Dusty

Dust Free

Galaxies appear to become less dusty at high redshift


Star Formation Rate (SFR) History to z~6

Dust Corrected

Uncorrected Log

10

Msol

yr-1 Mpc-3

Dust-corrected SFR shows a much more significant drop to high redshift than uncorrected.


Most Significant DustCorrections

Can the galaxies at z~6 reionize the universe?

C=<2>/<>2=10


fesc,rel = 0.2 (Shapley et al. 2006, in prep)

dM*/dt = 0.043 (needed)

Theory

dM*/dt ≈ (0.052)(C30)(0.5/fesc,rel)((1+z)/7)3

(Madau et al. 1998)

C=<2>/<>2=10



Use Bouwens et al. (2006) LF at z~6


Theory Observations

dM*/dt = 0.043 (observed)

dM*/dt ≈ (0.052)(C30)(0.5/fesc,rel)((1+z)/7)3

(Madau et al. 1998)


C=<2>/<>2=10



Yes, it appears they can



Theory Observations


dM*/dt ≈ (0.052)(C30)(0.5/fesc,rel)((1+z)/7)3

(Madau et al. 1998)


C=<2>/<>2=10



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).



Theory Observations


dM*/dt ≈ (0.052)(C30)(0.5/fesc,rel)((1+z)/7)3

(Madau et al. 1998)


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

JAB ~ HAB ~27 mag

z ~7 galaxies selected from the UDF + UDF-IR (~6 arcmin2)



● 5 candidate z-dropouts

Two-color dropout selection


● – 1±1 contaminants

~1-2 z~7 galaxies

ACS NICMOS

JAB ~ HAB ~27 mag

z ~7 galaxies selected from the UDF + UDF-IR (~6 arcmin2)


● – 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

(1+z) 4 cosmological surface brightness

dimming


From z~6 sample

Log10 Msol yr-1 Mpc-3

Our cloning simulations predict: ~6 z-dropouts (assuming no-evol from z~6) find ~2 objects


HUDF z~7 result


Luminosity Density

(Star Formation Rate Density - no extinction)


Galaxies at z~10 (J-dropouts)



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 DickinsonHDF-N Thompson

HDF-S Parallel

H~28.1 mag, 0.8 arcmin2




UDF Parallel #1 UDF Parallel #2

H~28.5 mag, 1.3 arcmin2 H~28.5 mag, 1.3 arcmin2

5, AB mags


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


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


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)


● Our cloning simulations predict ~5 J-dropouts ● (assuming no-evolution from z~6)

If none of thecandidates are at z~10

“Cosmic Variance” due to LSS is ~19% RMS.



Log10

Msol

yr-1Mpc-3

Bouwens, Illingworth, Thompson, Franx 2005aCosmic 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 NICMOSAB > ~ 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 arcmin2 of very deep optical + IR area

Galaxies at z~7 revisited (z-dropouts)



A few new z ~ 7 candidates

V i z J H

DetectionNo Detection




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)


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


Cloning Procedure ●WMAP cosmology

(B/V/I color images)

(1+z) 4 cosmological surface

brightness dimming


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. 1998Cosmic 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 disks2% in late-type galaxies

Key issue at high-redshift (z>2):

identifying and characterizing spheroid (bulges and Es)

disk formation (precursor buildup?)


Arc

Simulation - showing the region around a rich cluster at z~1.4

Large Scale Structure

Springel et al 2005 millennium simulationCosmic 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


N HST ACS UDF Rychard Bouwens & Garth Illingworth Galaxies and Structures through Cosmic Times...

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