The Properties of LBGs at z>5Matt Lehnert (MPE)

Malcolm Bremer (Bristol)Aprajita Verma (MPE)

Natascha Förster Schreiber (MPE)and

Laura Douglas (Bristol)

Programs to Study z>5 LBGs

Deep Imaging and Spectroscopy of 4 fields of about 160 arcmin2 with FORS2 on VLT

ESO Large Program of Deep Imaging and Spectroscopy of 10 EDisCS fields

Deep Spectroscopy of CDFS with GMOS on Gemini-South

Pilot program to use GOODS-South IRAC data

The VLT survey: LP + GO

•10 widely separated fields with deep VRIZJK data and HST I band + IRAC (~400 arcmin2)

•Originally observed as part of the EDisCS cluster survey. Clusters usually low mass, lensing not a problem.

• 4 Contiguous fields with deep RIZ+IRAC (~160 arcmin2)

•Spectroscopy with the VLT, 1 to 5 masks each, depending on the richness work is still on-going

LBGs at z>5• Example of six targets with

measured redshifts.

• All are R-band drop outs

RRABAB>27.8 and (R-I)>27.8 and (R-I)ABAB>1.5>1.5

Spectroscopic limit: ISpectroscopic limit: IABAB<26.3<26.3

Selected to match z~3 LBGsSelected to match z~3 LBGs

LBGs at z>5

BDF1:10 z=5.774 8191.8Ǻ

8083.0ǺBDF2:19 z=5.645

7315.5ǺBDF1:18 z=5.017

8351.4ǺBDF1:19 z=5.870

7362.0ǺBDF1:26 z=5.056

Example: One spectroscopically-completed field

“Priority 1+2”

targets

Example: One spectroscopically-completed field

Spectroscopicallyconfirmedtargets

Redshifts in this one field

Spike in the redshift distribution at z~5.1

Num

ber

Redshift

9 sources

Distribution of sources in this one field

3-D distribution of objects

X-Y projection of z=5.1

X-Y projection of all

GOODS/CDFS

• Lyman break colour selection (HST/ACS)– V-band dropouts V-I>1.7 – IAB<26.3 (comparable to our spectroscopic limit)– 3 non-detection in F435W (B)

• 10 band multi-wavelength photometry– selection HST/ACS BVIz– VLT/ISAAC deep NIR JKs – Spitzer/IRAC deep MIR 3.6 4.5 5.8 8m

4.6<z<5.9

109 galaxies, stars & QSOs

Or, an exercise in determining uncertainties and error analysis …

Typical SED & SED modelling

Properties of z>4.6 LBGsMulti-variate fit to SED ─ average probability distribution of most robust photometry ─ 21 sources

Bruzual & Charlot (2003)

Salpeter IMF

SMC-type extinction

Z=0.2 Z

3 SFH:

Instantaneous burst

e-(t/) with =300Myr

Constant SF (to maximize ages)

M

zphot

Properties of z>4.6 LBGs

Nagamine et al. (2006)

Contribution to the star-formation history

determined using full SED

Properties of z>4.6 LBGs

Rudnick et al. (2006)

>0.5% of stellar mass in place at z~5

Evolution of the stellar mass density

Duty cycle ~10?

Properties of z>4.6 LBGs

Papovich et al. (2001), Heckman et al. (2005)

Intensity of UV selected starbursts over a range of epochs

log

SF

R (

M y

r-1 k

pc-2

)

Redshift

Winds

Properties of z>4.6 LBGs

Scannapieco et al. (2003), Songaila (2001)

ρSF~0.06 M yr-1 Mpc-3

Ώbh2=0.023

closure density

dMSF/dt ≈ dMwinds/dt

Z/Z≈0.2

Ncycle ≈ 10

f* = 0.5

f* = 0.1

f* = 0.01

Contribute significant metals to the IGM?

SummaryRedshifts of well over 50 LBGs in ESO programs – more to come – more IRAC data to come

tUV,optical < 100 Myrs and AV<0.3 (strong Ly emitters)

MSED few x 109 M (10x < Mz3 LBGS)

Star-formation rates = ~10 to ~100-200 M yr-1

zformation < 6-7 for majority, some earlier

Ncycles ≈10

Likely drive vigorous winds (early enrichment?)