nod & shuffle at magellan lcir survey update october 18 2002 gdds preview

Nod & Shuffle at Magellan

LCIR Survey Update

October 18 2002

GDDS Preview

Conventional Slit Spectroscopy

• Sky subtraction is primary limitation– Slit irregularities– Flat-field errors– Residual Fringing– Geometric distortions– Low slit density on sky

• Beam switching ?– Variable sky spectrum– Read noise penalty– High read-out overhead

• The solution: ‘nod & shuffle’

Obscured Charge

Storage Area

Obscured Charge Storage Area

First Exposure

Active slit area

“A” position

“B” position

Now nod telescope and shuffle charge

Nod & shuffle the other way

“A” position

“B” position

Repeat N times and then readout

Difference of two positions

Finally shift and add both

LBL High Resistivity CCDs


No fringing, but high CR rates


Straight average - 2 hours Nod & Shuffle


+/- 200 DN rejection

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

GMOS N&S 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

GMOS Nod&Shuffle Multislit

Maximum Slit Utilization

Nod & Shuffle on IMACS

Nod & Shuffle on IMACS

2’’ slits

2’’ gaps

Micro-Shuffling on IMACS

2” slits

2” gaps

4000A per

spectrum

Micro-Shuffling on IMACS

Macro-Shuffling on IMACS

High Slit Density or IFU mode

Technical and Practical Considerations• Telescope, Guider and CCD controller must be

well synchronized

• Active Optics must work with short dwell time

• Overheads must be minimized

• Mask making software needs special capabilities• Reduction software (done! - Abraham & Glazebrook)

• Order blocking filters?

Las Campanas IR Survey

McCarthy, Persson, Martini, Koviak (OCIW)

Chen (MIT), Marzke(SFSU), Carlberg, Abraham(UT)

Ellis (Caltech)

Evolved Galaxies at

1 < z < 2

Las Campanas IR Survey

• Goal: Empirical understanding of early galaxy evolution

• Target: 1 square degree to K = 21

• Pilot survey in 2000/2001: VRIH to H=20.5

• Six fields around the equator (2 in south!)

• 1 square degree in BVRIz’H

• 0.5 square degrees in J & K to K = 20.8

• 200+ redshifts with LDSS2

• ~ 50 redshifts with GMOS & LRIS

Color-Magnitude Diagram

Stars

0.0 < z < 1.0

1.0 < z < 1.5

1.5 < z < 2.0

500 sq. arcmin

Color-Color Diagrams

• Stars form distinct sequence

• Z > 1 galaxies appear at K ~ 19

• Z > 1.5 galaxies at K > 20.5



• Z < 1 galaxies well sampled at K ~ 19




• Z > 1.5 galaxies at K > 20




• Z > 1.5 galaxies at K > 20

• Reddest galaxies follow minimal evolution track

Color-Redshift Diagrams

Photometric Redshifts from LCIR

Clustering of Red Galaxies

Evolving Luminosity Functions• LFs derived from photo-

z’s with modified likelihood approach

• LF at intermediate z agrees well with CNOC2

• Very little apparent evolution in L* to z ~ 1.2

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

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 mask84 objects 2 tiers with150 l/mm grating

GDDS Spectra77 objects 40,000 secs

GDDS Nod&Shuffle Mask

[OII] Redshifts from GDDS

23.7 < I(AB) < 24.2

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!

Photometric Redshifts from LCIR

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

At least halfway across the desert!!

Again just the easy ones…

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

nod & shuffle at magellan lcir survey update october 18 2002 gdds preview

Documents

reddest galaxies

imacshigh slit density

intermediate z

ifu modemacroshuffling

imacsnod shuffle

shuffle chargenod

lcirphotometric redshifts

s exposure10