1 / 19

dwarf elliptical galaxies (again)

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

liana
Download Presentation

dwarf elliptical galaxies (again)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. dwarf elliptical galaxies(again) Dolf MichielsenSchool of Physics & Astronomy

  2. 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

  3. 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

  4. 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

  5. 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)

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

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

  8. ITP – structural parameters • C,A,S – age, met, ZMgb/Z<Fe> • selection effect on field dEs

  9. ITP – environment Virgocentricdistance ‘special’ cases • bluenuclei • disks • rotation

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

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

  12. 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

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

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

  15. VLT – the calcium puzzle IIIc • SSP spectral fit with Pegase-HR + Elodie FCC 150 very weakemission - 1

  16. VLT – the calcium triplet IV • SSP results

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

  18. 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.

More Related