The Properties of LBGs at z>5
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Transcript of The Properties of LBGs at z>5
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The Properties of LBGs at z>5Matt Lehnert (MPE)
Malcolm Bremer (Bristol)Aprajita Verma (MPE)
Natascha Förster Schreiber (MPE)and
Laura Douglas (Bristol)
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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
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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
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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
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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
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Example: One spectroscopically-completed field
“Priority 1+2”
targets
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Example: One spectroscopically-completed field
Spectroscopicallyconfirmedtargets
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Redshifts in this one field
Spike in the redshift distribution at z~5.1
Num
ber
Redshift
9 sources
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Distribution of sources in this one field
3-D distribution of objects
X-Y projection of z=5.1
X-Y projection of all
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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 …
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Typical SED & SED modelling
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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
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Properties of z>4.6 LBGs
Nagamine et al. (2006)
Contribution to the star-formation history
determined using full SED
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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?
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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
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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?
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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?)