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