dwarf elliptical galaxies again

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dwarf elliptical galaxies(again)

• Dolf MichielsenSchool of Physics Astronomy

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dwarf elliptical galaxies (dEs)

• first observations inthe 1940s of the dSphs and
  dEs in the Local Group
• detailed observations since the 1980s with CCDs
  large telescopes
• dwarf galaxies aremost common typeof galaxy
• whole zoo of dwarf galaxies? what is their
  connection (if any) ?

Ferguson Binggeli 1994
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dwarf elliptical galaxies (dEs)

• first observations inthe 1940s of the dSphs and
  dEs in the Local Group
• detailed observations since the 1980s with CCDs
  large telescopes
• dwarf galaxies aremost common typeof galaxy
• whole zoo of dwarf galaxies? what is their
  connection (if any) ?

?
Ferguson Binggeli 1994
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dEs environment

• dEs are (almost) only found in dense
  environments in clusters and around giant
  galaxies
• morphology-density relation for dwarfs
• environment veryimportant in formationand
  evolution

Binggeli et al.1987
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stellar populations in dEs

• Not many studies done yet ? dEs have low surface
  brightness? high S/N needed for population
  studies
• Some work using ? narrow-band filters (Rakos et
  al. 2001, 2004, 2006)? surface brightness
  fluctuations (Jerjen, 2004)? spectra of compact
  objects and nuclei (higher surface brightness)
  (Mieske, 2006)? 2D spectroscopy (Chilingarian,
  2007)
• dEs seem to form a heterogeneous population with
  a wide spread in ages and metallicities
• More, consistent, age/metallicity estimates are
  needed, preferably using (optical) spectroscopy
• MAGPOP-ITP on dwarf galaxies (Virgo field)
• VLT FORS spectroscopy of dEs (Fornax groups)

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ITP optical spectroscopy

• 26 dEs in Virgo field
• ages, metallicities,enhancement? H Balmer
  Mg,Fe

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ITP C/N/Ca vs Fe

• compare to Es, GCs of an E,GCs of a dE

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ITP structural parameters

• C,A,S age, met, ZMgb/ZltFegt
• selection effect on field dEs

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ITP environment

• Virgocentricdistance
• special cases
• bluenuclei
• disks
• rotation

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ITP future

• more data available
• spectroscopy see talks of Elisa Javier
• imaging see talk of Reynier

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VLT the calcium puzzle I
CaT - ? anti-correlation
Too high CaT values for expected age metallicity
Michielsen et al. 2003
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VLT the calcium puzzle II

• Ages metallicities based on
• low-resolution spectroscopy (HeldMould 94)
• narrow-band imaging (Rakos et al. 2001)
• New optical spectroscopy with VLT FORS
• Michielsen, Koleva, Prugniel, Zeilinger, De
  Rijcke, Dejonghe, Pasquali, Ferreras
  Debattista, ApJL, accepted

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VLT the calcium puzzle IIIa

• SSP spectral fit with Pegase-HR Elodie

FCC 043 normal - 12
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VLT the calcium puzzle IIIb

• SSP spectral fit with Pegase-HR Elodie

FCC 046 emission - 3
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VLT the calcium puzzle IIIc

• SSP spectral fit with Pegase-HR Elodie

FCC 150 very weakemission - 1
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VLT the calcium triplet IV

• SSP results

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VLT the calcium puzzle V

• Solving the puzzle
• Consistent with use of CaT as metallicity
  indicator in Local Group GCs dSphs

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conclusions

• dEs have a range in ages metalliticies
• in general younger and less metal-rich than Es,
  and have solar ?/Fe ratios
• age and assymmetry seem to correlate with
  environment, suggesting an infall scenario of
  dIrr ? dE transformation.
• new age/metallicity estimates solve the calcium
  puzzle, at least for dEs.