GEMS Collaboration Meeting

Baltimore, Jan 20-21, 2003

What do we want to accomplish?

Get to know each otherTake stock of our status quo

–Data, software (tools),goals,...

Better define data productsPrioritize science goals

–Define approach–Clarify team responsibilities–(Re-)define schedule

GEMS vs. Other current activities

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Galaxy Population over the last 10 Gyrs

How many stars have formed since z~1.2 ?

– In which Galaxies? – Mostly during in star-bursts, or “quiescently”?– Which galaxies are “old” already?

How did the clustering of galaxies evolve ?– Mass clustering vs. galaxy bias.– Always a morphology-density relation?

When and how did bulges and disks form ?– How did the merger rate evolve?– Is there an „angular momentum“ problem– Do disks grow inside out?

What makes AGNs light up?– Dramatic drop in AGN lum. density since z~1

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What Data do we Need ?(to tackle this via “look-back” observations)

Galaxy properties as a function of:– Redshift/Epoch with t/tH ~1

Note: z=1.2 t look-back = 10 Gyrs

– Luminosity– Spectral Energy Distribution (SED)– Internal structure (size, bulge-to-disk, etc.)– Environment a multi-dimensional parameter space

+ account for large-scale fluctuation in the galaxy and mass distribution.

+ include “typical” galaxies at all epochs i.e. reach below L* at all redshifts

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Survey Requirements

Several 10,000 galaxies with– Redshifts to z>1 (good to a few

percent)

– Faint flux limit mr~24

– SEDs, including (rest-) UV and optical

Several large fields– Co-moving size > 5 Mpc

High-resolution (0.1”) imaging– typical scale lengths are 0.3 asec– two-color rest-frame B at all z

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Existing Faint Surveys

CFRS – Lilly, LeFevre, et al. – I<22.5, 591 galaxies

CNOC2– Yee, Carlberg etal.– R<21.5, z<0.55,2000 galaxies

HDF– Williams etal., Cohen etal. – redshifts for 200 objects

Medium Deep Survey – Keck spectroscopy

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CFRS Luminosity Function

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Status quo: Morphologies

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Status quo: bars

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Status quo: Bulge-Disk Fitting:GIM2D(Simard etal 1999)

Data:

somewhat heterogeneous HST imaging

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Status quo: disk sizes

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Status quo: Disk size functionLilly et al 1998 HST images of CFRS galaxies

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Status quo: merger rate

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Surveys at Hand

COMBO-17 C. Wolf, K. Meisenheimer (co-PIs), E. Bell, C.

Maier, H.-W. Rix, S. Phleps, A. Borch + Edinburgh, Bonn

– Data from WFI at the MPG/ESO 2.2m on La Silla

GEMS – 2-color, deep HST/ACS mosaic ( ~180 x HDF

area)

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GEMS: Key to “internal structure”(Galaxy Evolution from Morphology and SEDs)

Large HST program (125+50 orbits) to image “extended-Chandra-Deep-Field-South”

– 10,000 redshifts from COMBO-17– 9x9 ACS tiles 150 x HDF– V and z

– Limit: mz~27.5

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GEMS 58

1.5% of total

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COMBO-17 (~0.7”) vs. HST/ACS

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..and we do have the redshifts..

~1.2´x 2.2´ (0.003 of the total field)

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GEMS: Top-Level Project Steps

Image acquisision, reduction Object Detection+Match-up

Fitting/Morphology quantification

Selection/fitting simulation Structural „master catalog“

Empirical results Link to theoretical predictions Model-dependent results

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GEMS Analysis: Basic Steps

Task Responsible Date

Complete (%)

Data Acquistion

Caldwell, Vick, Peng

100% P ~95% E

Tile Reduction

Caldwell ~90% D~50% E

Object Detection

McIntosh ~90% D ~20% E

Galfit Code Peng Häußler,Jogee

~95% D

GIM2D McIntosh ~95% D

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Task ahead: Fitting 30,000 galaxies

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GEMS vs past work

30-fold number increase Well defined sample with ample

external information z-band ACS imaging

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Our competitive edge

COMBO-17 full catalog not yet published

GEMS mosaic largest HST image mosaic of sufficient depth (perhaps for a while...)

Comprehensive team experienceBUT..... GEMS data instantly public With DEEP and VMOS, the COMBO-17

data will loose their uniqueness within a year

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Top-Level Science Goals

How did stellar disks evolve/grow?– (Disk) size function

– L vs reff , Tully-Fisher

Evolution of bulges/ellipticals– B/D ratios, growth of „old“ pops.

– L vs reff , fundamental plane

Evolution of merger rate vs star burst rate

Did „internal evolution“ play a role?– Bar statistics

When are galaxies AGNs?– Host galaxies

What do we want to accomplish?

Get to know each otherTake stock of our status quo

–Data, software (tools), responsibilities

Better define data productsPrioritize science goals

–Define approach–Clarify responsibilities–(Re-)define schedule–set of possible 1.generation papers

GEMS vs. Other current activities

26

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Spectroscopy goals for COMBO-17/GEMS

Redshifts – outliers?– present median precision 180 Mpc– GEMS image contains 6 x more galaxies with

good photometry Spectral features

– Balmer emission/absorption lines– AGN vs. star-formation diagnostics

Kinematics– Stellar and emission lines

(stellar) masses from SEDs, spectra and kinematics

Star-formation rates and metallicity

Interaction rates – local velocity dispersion