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Properties of the Bright and Dwarf Galaxy Populations in Nearby Clusters

Properties of the Bright and Dwarf Galaxy Populations in Nearby Clusters. Rubén Sánchez-Janssen (IAC) J.Alfonso L. Aguerri Casiana Muñoz-Tuñón. Estallidos V, Granada, 2007. Dressler (1980). Butcher & Oemler (1984). Introduction.

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Properties of the Bright and Dwarf Galaxy Populations in Nearby Clusters

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  1. Properties of the Bright and Dwarf Galaxy Populations in Nearby Clusters Rubén Sánchez-Janssen (IAC) J.Alfonso L. Aguerri Casiana Muñoz-Tuñón Estallidos V, Granada, 2007

  2. Dressler (1980) Butcher & Oemler (1984) Introduction • What drives galaxy evolution? Does the environment really matters? • Galaxy clusters are ideal laboratories.

  3. Introduction • What drives galaxy evolution? Does the environment really matters? • Galaxy clusters are ideal laboratories. • Many processes may be responsible: ram-pressure stripping, tidal interactions, starvation, preprocessing... Is there a dominant one?

  4. The sample • SDSS DR5 - ugriz imaging and spectroscopy. • Sample of 88 nearby (z<0.1) clusters: ~11000 galaxies! • Detailed membership allows study of segregations, dynamics... A2199

  5. The Bright Population: VDPs • u-r = 2.22 separates early- and late-types (Strateva et al. 2001). • BCGs: • Core regions. • Very small velocity dispersions. • Reflect past merging and accretion history (Biviano & Katgert 2004).

  6. The Bright Population: VDPs • u-r = 2.22 separates early- and late-types (Strateva et al. 2001). • Early-types: • Highest fraction (62%). • Inner cluster regions (M-D relation). • Flat VDPs with mild outwards decline.

  7. The Bright Population: VDPs • u-r = 2.22 separates early- and late-types (Strateva et al. 2001). • Late-types: • Not so radially concentrated. • Higher values of  with decreasing VDPs. • Population on more anisotropic and radial orbits.

  8. The Bright Population: fb • Fraction of blue galaxies provides clues on evolution of SF.

  9. The Bright Population: fb • No clear correlation with global cluster properties. • Slight trend with Lx might indicate that the effects of the global cluster potential are only important in massive clusters (?).

  10. The Dwarf Population: DGR • Dwarfs: Mr > M*+1 • Giants: Mr < M* • Dwarf to Giant Ratio (DGR) grows in outer (less dense) regions. • Result of blue dwarfs having a more extended (less concentrated) distribution: avoid cores. • Red dwarfs have a flat distribution (constant LF faint-end slope, see Popesso et al. 2006). But not in equilibrium!

  11. The Dwarf Population: Colors • Red dwarfs have colors independent of environment, same of field. • Blue dwarfs are redder within r200, similar to field outwards. • Existence of a processes that converts blue dwarfs into red ones.

  12. Conclusions • Environment definitively plays a role, responsible mechanism difficult to disentangle. • Global cluster mechanisms (ram-pressure, cluster potential) might be only important in massive clusters, and mainly for dwarf systems. • Local environment might be the main responsible of bright galaxy evolution (group preprocessing). • Tidal effects (harassment) might turn blue dwarfs into redder systems.

  13. SEE YOU IN TENERIFE!

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