1 / 18

Globular Clusters: The Dwarf Galaxy Contribution

Globular Clusters: The Dwarf Galaxy Contribution. Eva K. Grebel Astronomisches Rechen-Institut (ARI) Center for Astronomy, Heidelberg University ( ZAH ) Heidelberg, Germany. van den B ergh (1995): stronger trend with perigalactic distances. Halo disk/bulge. –0.8 dex. Zinn 1985.

gizi
Download Presentation

Globular Clusters: The Dwarf Galaxy Contribution

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. Globular Clusters: The Dwarf Galaxy Contribution Eva K. Grebel Astronomisches Rechen-Institut (ARI) Center for Astronomy, Heidelberg University (ZAH) Heidelberg, Germany Globular Clusters: The Dwarf Galaxy Contribution

  2. van denBergh (1995): stronger trend with perigalactic distances Halo disk/bulge –0.8 dex Zinn 1985 bulge/disk GCs old halo GCs “young” halo GCs Sgr GCs Globular Clusters: The Dwarf Galaxy Contribution Harris 1996 Mackey & Gilmore 2004

  3. Cumulative radial distribution of different subcomponents Mackey & van den Bergh 2005 Globular Clusters: The Dwarf Galaxy Contribution

  4. Horizontal Branch Morphology vs. Metallicity: Age? Zinn 1993 Globular Clusters: The Dwarf Galaxy Contribution

  5. Horizontal Branch Morphologies and Young Halo Contributors t = 0 Gyr Mackey & Gilmore 2004 t = 1.1 Gyr t = 2.2 Gyr See also Harbeck et al. 2001 Globular Clusters: The Dwarf Galaxy Contribution

  6. Horizontal Branch Morphologies and Young Halo Contributors t = 0 Gyr Mackey & Gilmore 2004 t = 1.1 Gyr t = 2.2 Gyr See also Harbeck et al. 2001 Globular Clusters: The Dwarf Galaxy Contribution

  7. Horizontal Branch Morphologies and Young Halo Contributors t = 0 Gyr Mackey & Gilmore 2004 t = 1.1 Gyr t = 2.2 Gyr See also Harbeck et al. 2001 Globular Clusters: The Dwarf Galaxy Contribution

  8. SMC: Only nearby dwarf with only one, younger GC. (HST/ACS) Glatt et al. 2007 Globular Clusters: The Dwarf Galaxy Contribution

  9. 4 (out of 5) globular clusters in Fornax: ~ indistinguishable in age; as old as oldest Galactic globulars (relative age dating). Buonanno et al. 1998 Globular Clusters: The Dwarf Galaxy Contribution

  10. Age Difference vs. Metallicity bulge/disk GCs old halo GCs “young” halo GCs Sgr GCs Old halo: slight trend (towards bulge) Young halo: steeper trend(towards Sgr) Salaris & Weiss 2002 Harris 1996 Mackey & Gilmore 2004 Globular Clusters: The Dwarf Galaxy Contribution

  11. Lower [/Fe] at a given [Fe/H] in dwarfs and their globulars (few exceptions, e.g., Hodge 1; NGC 121) Cf. inner/outer halo dichotomy (Carollo et al. 2007) Sbordone et al. 2007 Globular Clusters: The Dwarf Galaxy Contribution

  12. Narrow peak; Age ~ –2 Gyr. Bimodal; peaked at –3.25 and –0.75 Gyr. Strongly peaked at Age ~ M92. Younger tail (incl. CMa?) Globular Clusters: The Dwarf Galaxy Contribution Mackey & Gilmore 2004 Salaris & Weiss 2002

  13. Similarity of Core Radii of Young Halo and External GCs Mackey & Gilmore 2004 If dwarfs were accreted: would contribute mainly young halo GC; only 20 – 20% old halo GCs. Zinn 1993 Globular Clusters: The Dwarf Galaxy Contribution

  14. Tidal Radii for Clusters of Different Components Rt: strongly correlated with a GC’s peri- galactic distance (van den Bergh 1994). Mackey & van den Bergh 2005 Globular Clusters: The Dwarf Galaxy Contribution

  15. “Vital Diagram” for Galactic Globular Clusters Gnedin & Ostriker 1997 Globular Clusters: The Dwarf Galaxy Contribution

  16. Half-light Radii vs. Absolute Magnitudes Cores of dwarf galaxies? sharp edge Mackey & van den Bergh 2005 Globular Clusters: The Dwarf Galaxy Contribution

  17. Globular clusters are rare in dwarfs! Globular Clusters: The Dwarf Galaxy Contribution Grebel 2002

  18. Some points for discussion: • Young halo globulars (HB morph.) resemble dSph globulars • BUT: a number with "old" HB morphologies • DSphs (and dIrrs) contain some of the youngest globulars known • BUT: Also contain globulars as old as oldest Galactic GCs • Half-light and tidal radii of young halo GCs and GCs in dwarfs: Close similarity. • Hint of accretion or effect of survivability in absence of major tidal disruption? • Overall metallicities of outer halo GCs and dwarf GCs: similar; low. • Lower [/Fe] at given [Fe/H] in dwarf field stars and GCs. (Constrains number of accretion events) • GCs in MW with similar ratios: Assumed to be accreted (e.g., Sgr) • BUT: Also (d)Irrs contain some GCs with enhanced [/Fe]! • Accretion: consistent. But is it required? • Substructure problem; number, importance, time of accretion events • How can GCs form in dSphs in the first place? Why so rare? Globular Clusters: The Dwarf Galaxy Contribution

More Related