2. dwarf elliptical galaxies (again) Dolf Michielsen School of Physics & Astronomy

3. dwarf elliptical galaxies (dEs) first observations in the 1940s of the dSphs and dEs in the Local Group detailed observations since the 1980s with CCDs & large telescopes dwarf galaxies are most common type of galaxy whole ‘zoo’ of dwarf galaxies  what is their connection (if any) ? Ferguson & Binggeli 1994

4. dwarf elliptical galaxies (dEs) first observations in the 1940s of the dSphs and dEs in the Local Group detailed observations since the 1980s with CCDs & large telescopes dwarf galaxies are most common type of galaxy whole ‘zoo’ of dwarf galaxies  what is their connection (if any) ? Ferguson & Binggeli 1994 ?

5. dEs & environment dEs are (almost) only found in dense environments: in clusters and around giant galaxies morphology-density relation for dwarfs environment very important in formation and evolution Binggeli et al.1987

6. 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)

7. ITP – optical spectroscopy 26 dEs in Virgo & field ages, metallicities, enhancement  H Balmer – Mg,Fe

8. ITP – C/N/Ca vs Fe compare to Es, GCs of an E, GCs of a dE

9. ITP – structural parameters C,A,S – age, met, Z Mgb /Z selection effect on field dEs

10. ITP – environment Virgocentric distance ‘special’ cases bluenuclei disks rotation

11. ITP – future more data available spectroscopy: see talks of Elisa & Javier imaging: see talk of Reynier

12. Michielsen et al. 2003 VLT – the calcium puzzle I CaT* -  anti-correlation Too high CaT values for expected age & metallicity

13. VLT – the calcium puzzle II Ages & metallicities based on –low-resolution spectroscopy (Held&Mould 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

14. VLT – the calcium puzzle IIIa SSP spectral fit with Pegase-HR + Elodie FCC 043 ‘normal’ - 12

15. VLT – the calcium puzzle IIIb SSP spectral fit with Pegase-HR + Elodie FCC 046 emission - 3

16. VLT – the calcium puzzle IIIc SSP spectral fit with Pegase-HR + Elodie FCC 150 very weak emission - 1

17. VLT – the calcium triplet IV SSP results

18. VLT – the calcium puzzle V Solving the puzzle… Consistent with use of CaT as metallicity indicator in Local Group GCs & dSphs

19. 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.