the gemini deep deep survey first results karl glazebrook johns hopkins university
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The Gemini Deep Deep Survey
First Results
Karl Glazebrook
Johns Hopkins University
GDDS Team: Karl Glazebrook (JHU), Bob Abraham (Toronto), Pat McCarthy (OCIW), Rick Murowinski (DAO), Ray Carlberg (Toronto), Ron Marzke SDSU), Sandra Savaglio (JHU), H-W Chen (OCIW), David Crampton (DAO), Isobel Hook (Oxford), Inger Jørgensen & Kathy Roth (Gemini)
This talk• Current galaxy populations z<1 & z>2
– Evolution to z=1 of classical E/Sp– Lyman Break Galaxies (LBGs) at z>2
• The ‘redshift desert’ 1<z<2– Why is it there?– What can we do about it?
• Technical solution: ‘nod & shuffle’• The Gemini Deep Deep Survey
– Selection– Observations– Results
The redshift desert
Redshift
n(z)Caltech FGRS
CFRS
R<24LBGsR<25
What are these populations?ALL MAGSARE AB!`
z<1 galaxies: SFR-z
(1+z)3
(1+z)2
Slope allowed by
local population synthesis‘cosmic spectrum’
2dFGRS: Baldry et al.
SDSS: Glazebrook et al.
Measurements:
Luminositydensities:
Radio FIR
H, H
[OII]
UV cuum (~2800Å)
Orig. (1+z)4
(Lilly et al. 1996)
z<1 galaxies: morphology
z<1 galaxies: morphological evolution
Brinchmann et al.
(1998,2000)
z
mor
phol
ogy
z<1 galaxies: morphological evolution
Brinchmann et al. 1998
z<1 galaxies: morphological evolution
Brinchmann et al. 2000
Massive galaxies in place at z=1Possible CDM contradictionWhat about z>1 ?
‘Stellar’Mass
z>2 galaxies: selection
Steidel et al.
Populationappears R>23.5
z>2 galaxies: morphology
Irregular morphology (Dickinson et al.)
When does Hubble Sequence form?
Opt. NIR Opt. NIR
z>2 galaxies: SFR-z• Data from low to high
redshift: Lilly et al., Connoly et al., Madau et al., Steidel et al.
• 1<z<2 filled in by photometric z’s
• Dust corrections in z>2 Steidel et al. samples estimated from H/UV in a few galaxies.
• Decline probably isn’t real. photo-z’s
Steidel (1999)
z>2 galaxies: masses
K data at z=3 probes rest frame V not ideal
Optical + NIR photometry: best fit masses 109-1011M
c.f. modern galaxies: 109-1012M
~ 10-20% of todays mass observed at z>2 ?
Papovich, Dickinson, Ferguson (2001)
photo-z’s
Steidel (1999)
Mass assemblySFR Mass
SFR (1+z)3 z<1 (1+z)1 z>1
= 0 z>5
SFR (1+z)3 z<1 = const. 1 z>1
= 0 z>5
27%
17%
The redshift desert
Redshift
n(z)
Caltech FRSCFRSR<24
LBGsR<25
Epoch of Mass assembly of galaxies?
Formation of Hubble Sequence?
Cause ?
Colors of current faint samples
Caltech FRS LBGs
E/S0
Sbc
SFR=const.
Why I: selection effect of redshift
Old stellar pop
Young stellar pop
z=0z=1.5 z=1
Galaxies especially elliptical galaxiesat z=1.5 are very faint!
Very very hard to get good signal/noise spectra
detect weak absn lines measure redshift
z=3
Why II: sky background
Gemini Observatory Sky Spectrum
Optical + near-IR
3500 4500 5500 6500 7500 8500 9500 10500 11500
Wavelength / Angstroms
z=0.5 z=1 z=1.5
Sky background is BRIGHTNOISY
Line emissionVARIES on 100s timescales
Objects are 100 fainterthan sky
Subtraction is very very hard
z~4 LBGs
Steidel et al 1999
I=24-25
z=1.5 radio galaxies
53W091 R=24.8 I=23.5Keck/LRIS 20ksec
~3L* E. galaxy
Model
Observed wavelength / Angstroms
+53W069
Simulated z=1.5 sub-L* elliptical
+ 1% sky-subtractionerror
2800Å
HK
Input Spectrum53W069, + Poisson noise.
Simulated I=25 z=1.5early-type spectrum
Exposure 100 ksecs(Gemini/GMOS)
Technical solution: ‘nod & shuffle’• Rapid nod of galaxy along slit (~60s) to give A/B
images• Store B image adjacent to A, using CCD charge-
shuffling no readnoise penalty• History:
– J.C. Cuillandre et al. 1994 ‘va et vient’ (NTT trials)– Sembach & Tonry 1996 (Dartmouth 2.4m)– Glazebrook & Bland-Hawthorn 1998 (AAT):
• MOS mode (200 m-plex in HDF-S to R=23.4• Demonstrate 10-4 sky/sky
• 2001: Implemented on Gemini/GMOS
Sky cancellation: ‘nod and shuffle’Storage of ‘sky’ image next to object image via ‘charge shuffling’Zero extra noise introduced, rapid switching (60s)
A
B
AB
Typically A=60s/15 cy: 1800s exposure10 subtraction
Another example
Gemini Deep Deep Survey
GDDS Team: Karl Glazebrook (JHU), Bob Abraham (Toronto), Pat McCarthy (OCIW), Rick Murowinski (DAO), Ray Carlberg (Toronto), Ron Marzke (SDSU), Sandra Savaglio (JHU), H-W Chen (OCIW) David Crampton (DAO), Isobel Hook (Oxford), Inger Jørgensen & Kathy Roth (Gemini)
Goal: Deep 100,000 sec MOS exposures on Las Campanas IR Survey fields to get redshifts of a complete K<22.4 I<25 sample covering 1<z<2
Goals:• First Complete sample 1<z<2
– use photo-z’s to weed out low-z galaxies (BVRIzJHK)
• Determine luminosity and mass functions– Can we see the assembly of mass? – Massive galaxies at z=2 would severely trouble CDM– Mass(z) more robust than SFR(z)
• Relate to galaxy morphology (ACS)– Identify Ell/Sp/Irr over 1<z<2– Track low-z behavior to high-z
• E.g. can we see mass assembly of giant Ellipticals?• Can we track the dynamical evolution of spiral disks
• Track SFH over 1<z<2: – Age of galaxies, metallicities of population
GDDS history• Sep 2001: start of GDDS evil planning• Jan 2002: team approached Gemini observatory with nod
& shuffle proposal• Feb 2002, obtained Gemini go-ahead.• Feb-May 2002. Implementation of N&S at DAO (~$10K
cost)• May 2002: first N&S engineering observations on 8m• July 2002: N&S commissioned on sky• Aug 2002: First 4 nights of GDDS Science Verification
for N&S success!!• Sep-Dec 2002: Band I queue time, 50 hrs
Gemini + GMOS
GMOS spectrographGemini
GMOSLRISLDSS1
Tel.+instr. efficiency
GMOS represents the best possible option for a red sensitive MOS. Ideal system for nod & shuffle
Sky residualsSUMMED along long slit (1.8 arcmin)
Raw Sky/20
Subtracted sky
(i.e. ~10 level is enough for 200,000 sec pointed obs.)
Cycle:A=60sB=60s
+ 25s o/head
GDDS sample LCIRS
4 fields BVRIzJHKs
2626Limits:B<26.0 V<26.5R<26.8 I<25.8z<24.7 J<22.5H<22.5 Ks<22.4
Use photo-z’s to weed out z<0.7 foreground
I<25 typical model n(z):
GDDS sampleLCIRS K<20.3 sample + photo-z’s
Burst=1=2const.
Red galaxies at high-z exist!
CNOC M* evol.
GDDS mask84 objects 2 tiers with150 l/mm grating
GDDS Spectra77 objects 40,000 secs
I=23.8
Example object: raw object+skyOH forest
I=23.8 z=1.07
Example object: N&S subtracted[OII] 3727at 7700Å
GDDS: Oct 2002 snapshot• GDDS SV Aug 2002 + Band I Queue time
(Sep/Oct 2002) Up to 100 ksec on first field (SA22)First 40 ksec now reduced and very preliminary redshifts
• TO COME 2002-2003 (total time awarded 50 hrs in Band I):Complete 3 GDDS fields, secure 100 z>1 redshifts
GDDS: ultra-super-preliminary results
These are just the‘easy’ ones so far!~ 40 ksec
Working on CCF
Data on this field is still coming in.
Full 100,000 secswill pound on z=1.5old red galaxies
High Redshift Elliptical Galaxies?
FeIIMgII
53W091 at z=1.393VI=2.2 IK=2.94
Model: 4 Gyr old stellar populationat z=1.4, age of Universe = 4.5Gyr
z(form) ≈10
Obj # 398 from GDDS SA22VI=1.7 IK=2.7
Wavelength / Angstroms
f
Rest-frame UV absorption line redshifts!
Accuracy of photo-z’s
First GDDS SA22field
Note: B data N/A for this one!!
Large scatter
Not too bad z<0.7
Colors of GDDS galaxies
GDDS
HDF LBGs (Papovich et al. 2001)
z=1.4 E/S0 template
z=1.4 Sbc template
Color-z of GDDS galaxies
E/S0 template
Sbc template
SFR=const. template
At least halfway across the desert!!
Again just the easy ones…
GDDS: observed evolution?
Ultra-super-duperpreliminaryLarge pinch
of salt
Determing IR luminosities: K correction
OldOld
Almost independent of spectral type for z<1.5, robust correction
starburst SEDsstarburst SEDs
IR luminosities of GDDS galaxies
K<17.9 local sample
(Glazebrook et al. 2003)
GDDS galaxies
M* z=0.1
IR luminosities II
MK
K<17.9 local z<0.5 sample(Glazebrook et al. 2003)
GDDS galaxies z>1
M* z=0.1
Masses of GDDS galaxies
K<17.9 local z<0.5 sample(Glazebrook et al. 2003)
K<17.9 local z<0.5 sample(Glazebrook et al. 2003)All GDDS galaxies
Mass-Redshift relation
K<17.9 local z<0.5 sample(Glazebrook et al. 2003)
GDDS galaxies
LBGs
GDDS: summary• GDDS hits complete sample at z>1
– Photo-z selection z>1 ~works
• Gets spectra via ‘nod & shuffle’ sky cancellation– Successfully commissioned July-Aug 2002, have data
on first (half) field
• Are we seeing a dearth of high mass galaxies at z>1 ? Possible epoch of mass assembly?
• TO COME 2002-2003:Complete 3 GDDS fields, secure 100 redshifts Apply for HST/ACS imaging for morphologies
Mass function vs Morphology vs z.
GDDS: seeking old
galaxies at z>1
z=1.4, IK=2.7