GEMS: The Evolution of Disc Galaxies

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GEMS The Evolution of Disc Galaxies

• Marco Barden

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Galaxy Evolution

• Archaeology ? Look-back approach
• Galaxy evolution ? Population evolution
• Important because
• Even in local universe 60-80 discs
• Most of all stars form in discs
• Most of the stars of the MW formed since z1
• ? measure structural parameters of discs as a
  function of time

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Theoretical Models

• Expectation from models (e.g. Mo, Mao, White
  1998, Bouwens Silk 2002) Discs in the early
  universe
• were more compact
• were on average brighter
• had higher surface brightness
• had lower stellar masses
• than disc galaxies today
• ? large redshift surveys to constrain models

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Observations

• Several surveys (e.g. CFRS, DEEP, GOODS)?
  controversy
• Strong SB evolution (result of higher overall
  SFR, Schade et al. 1996)
• No evolution in SB (selection effects, Simard et
  al. 1999)
• At z1 a new class of high SB galaxies (?0,elt17.7
  mag arcsec-2) appears (Simard et al. 1999)

Ravindranath et al. 2004
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Observations

• Restricted luminosity range? interpretation
• Surface brightness dimming ? selection effects
  dominate a high-z
• Objects are small ? high spatial resolution
  needed
• Distribution of surface brightness is wide ?
  large samples

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GEMS Galaxy Evolution from Morphology and SEDs

• MPIA Barden, Bell, Borch, Häußler, Heymans,
  Meisenheimer, Rix (P.I.)
• STScI Beckwith, Caldwell, Jogee, Somerville
• AIP Jahnke, Sanchez, Wisotzki
• Oxford Wolf
• UMass McIntosh
• U. Arizona Peng

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GEMS Galaxy Evolution from Morphology and SEDs

• E-CDFS
• Largest HST colour mosaic 30x30, 9x9 ACS
  tiles, 150 HDF
• 125 (GEMS) 50 (GOODS) orbits
• 2 filters
• F606W (mABlt28.3)
• F850LP (mABlt27.1)

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GEMS Galaxy Evolution from Morphology and SEDs

• 10000 redshifts from COMBO-17 (Wolf,
  Meisen-heimer et al. 2003)
• 5 broad / 12 medium band filters
• ?z0.02, 0.1ltzlt1.3, mrlt24
• SEDs (3500-9250Å)

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The Disc Sample

• Sersic fits to F850LP images with GALFIT (Peng et
  al. 2002)
• Selection of discs with nlt2.5
• Completeness ? simulations (Häußler et al. 2004)
• Size correction (de Jong 1996)

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Completeness Selection Effects
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The Magnitude-Size Relation
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The Magnitude-Size Relation
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The Magnitude-Size Relation
Trujillo et al. 2004
HDF
FIRES
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The Magnitude-Size Relation
?V(z)(21.24?0.08) - (1.79?0.11) z
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The Magnitude-Size Relation
Bouwens Silk 2002
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The Mass-Size Relation
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The Mass-Size Relation
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The Mass-Size Relation
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Conclusions

• The magnitude-size relation of disc galaxies
  changes as a function of redshift ? average SB
  increases
• The appearance of high SB galaxies at high-z is a
  result of the increasing average SB
• Disc galaxies at different redshifts follow the
  same mass-size relation ? galaxies form
  inside-out
• Mass densities stay roughly constant with redshift