Galaxy formation and evolution with a GSMT:

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• Galaxy formation and evolution with a GSMT
• The z0 fossil record
• 17 March, 2003

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Current Landscape

• The star formation, chemical evolution and
  dynamical histories of the Galaxy have been
  largely (though not completely) pieced together
  from studies of the kinematics and abundances of
  field stars and clusters.
• Starting with 4m-based photometry and now with 8
  and 10m high-dispersion spectroscopy similar
  studies have been extended to the Milky Way dwarf
  galaxy complement.

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Color-magnitude Studies of Star-Formation
Histories
Fornax Carina
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Current Landscape

• The star-formation histories of the Galaxys dSph
  have proven to be surprisingly diverse and so-far
  unexplained.
• To date, beyond the Local Group inferences about
  SFH and chemical evolution history have been
  based on integrated spectroscopy and photometry.
• 8/10m AO-based studies in their infancy.

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The role of a 30m

• Extend fossil record studies of resolved
  stellar populations to 15Mpc.
• Vastly larger samples across full Hubble
  Sequence.
• Environments ranging from field to Virgo
  Cluster-like density (core of the Coma I group).

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The Big Questions

• What are the star formation histories for M31
  M81 and their dwarf complements?
• Did star formation commence simultaneously
  throughout the Local Group?
• What are the key factors that govern dwarf galaxy
  star formation episodes?
• What are the complete chemical enrichment
  histories of Local Group galaxies?
• Fe/alpha/r-process compared to Galaxy. Inferences
  for IMF and feedback differences

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Big Questions cont.

• Directly measured star formation histories of
  giant elliptical galaxies.
• Is there a significant population of young stars
  in giant elliptical galaxies? (JWST?)
• Detailed mix of elements with different
  nucleosynthetic origins in a gE

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Big Questions cont.

• Did star formation commence at the same time
  throughout the volume of space to Virgo?
• Cosmic variance in SFH as a function of Hubble
  type/environment
• z0 population census is crucial for matching
  populations at larger z

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The role of a 30m Analysis Techniques

• Establish distance scale to Virgo Cluster to 10
  via RR Lyrae,TRGB observations
• CMD studies
• Main-sequence turnoff ages
• Fe/H and Fe/H spread from RGB morphology
• Horizontal branch morphology inferences for ages
• R5000 to 50000 spectroscopic studies
• Kinematics
• Detailed chemical compositions

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MSTO (10Gyr) V HB V RGB tip V
Absolute 4.5 0.8 -1
M31 28.8 25.1 22.3
M81 32.3 28.5 27.8
NGC 3379 34.5 30.8 29
Virgo 36 32.3 30.5
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MSTO (10Gyr) V/I/K HB level V/I/K RGB tip V/I/K
Absolute 4.5/3.8/3.2 0.8/0/-1.2 -1/-4/-7.5
M31 28.8/28.1/27.5 25.1/24.3/23.1 22.3/20.3/16.8
M81 32.3/31.5/30.9 28.5/27.8/26.6 27.8/24.8/20.3
NGC 3379 34.5/33.8/33.2 30.8/30/28.8 29/26/22.5
Virgo 36/35.2/34.7 32.3/31.5/30.3 30.5/27.5/24
What you shade in a table like this depends
strongly on MCAO performance
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30m
M81 Group
M31 Group
10m
4m
Galactic dSph
I15 20 25
30
Nearby GGC
Old MSTO magnitude
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Useful type of plot?
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Relevant numbers to collect

• Sample sizes broken down by Hubble Type as a
  function of distance (easy)
• S/N vs science for different studies (easy)
• Surface brightness/crowding limits and effects
  (hard). Olsen/Rigout work is an important
  contribution.

Good MCAO simulations are crucial to this area
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Capabilities requirements list

• Instrumentation
• R40000 optical/Near-IR spectroscopy
• MCAO/ modest-field JHK photometry
• AO
• PSF stability/strehl requirements require
  simulations
• Lambda regimes
• B through K

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What might be missing from current discussions?
Slide from November 2002 - are we getting
anywhere?

• Real simulations
• Crowding
• Effects of realistic PSF for AO photometry and
  spectroscopy
• Tools required for using diagnostics in the
  near-IR (CMD/abundances) - most of the gains will
  require AO with moderate or better strehl --
  likely only possible longward of 1 micron for the
  next few decades)
• Young stellar populations

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Would you build an ELT to do this?

• Perhaps not. 8/10m AO will make excellent
  progress throughout the Local Group and probably
  out the the M81 Group.
• Will we learn fundamentally new things extending
  to the 10Mpc groups and Virgo?
• If an ELT is there, these are excellent areas and
  excellent astronomy will be available.
• MSTO photometry throughout Local Group and
  stellar pops in a gE may be the greatest
  potential
• Sub-mas astrometry of faint objects