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Yayınlanmış 1 Ocak 2018 | Sürüm v1
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Abundance ratios in dwarf elliptical galaxies

Oluşturanlar

  • 1. Univ Groningen, Kapteyn Astron Inst, POB 800, NL-9700 AV Groningen, Netherlands
  • 2. Aix Marseille Univ, CNRS, LAM, UMR 7326, F-13388 Marseille, France
  • 3. ETH, Inst Astron, Wolfgang Pauli Str 27, CH-8093 Zurich, Switzerland
  • 4. Univ Vienna, Dept Astrophys, Turkenschanzstr 17, A-1180 Vienna, Austria
  • 5. Univ Oulu, Astron Res Unit, FI-90014 Oulu, Finland
  • 6. Heidelberg Univ, Zentrum Astron, Astron Rech Inst, Monchhofstr 12-14, D-69120 Heidelberg, Germany
  • 7. European Southern Observ, Karl Schwarzschild Str 2, D-85748 Garching, Germany
  • 8. Univ Pacific, Dept Phys, 3601 Pacific Ave, Stockton, CA 95211 USA
  • 9. Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany
  • 10. Ataturk Univ, Dept Astron & Astrophys, Fac Sci, TR-25030 Erzurum, Turkey

Açıklama

We determine abundance ratios of 37 dwarf ellipticals (dEs) in the nearby Virgo cluster. This sample is representative of the early-type population of galaxies in the absolute magnitude range -19.0 < M-r < -16.0. We analyse their absorption line-strength indices by means of index-index diagrams and scaling relations and use the stellar population models to interpret them. We present ages, metallicities, and abundance ratios obtained from these dEs within an aperture size of R-e/8. We calculate [Na/Fe] from NaD, [Ca/Fe] from Ca4227, and [Mg/Fe] from Mgb. We find that [Na/Fe] is underabundant with respect to solar, whereas [Mg/Fe] is around solar. This is exactly opposite to what is found for giant ellipticals, but follows the trend with metallicity found previously for the Fornax dwarf NGC 1396. We discuss possible formation scenarios that can result in such elemental abundance patterns, and we speculate that dEs have disc-like star formation history (SFH) favouring them to originate from late-type dwarfs or small spirals. Na-yields appear to be very metal-dependent, in agreement with studies of giant ellipticals, probably due to the large dependence on the neutron-excess in stars. We conclude that dEs have undergone a considerable amount of chemical evolution, they are therefore not uniformly old, but have extended SFH, similar to many of the Local Group galaxies.

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