Chania, Crete, August 2004 “The environment of galaxies”

1. Pierre-Alain Duc Recycling in the galaxy environment F. Bournaud J. Braine U. Lisenfeld P. Amram P. Weilbacher Chania, Crete, August 2004 “The environment of galaxies”

2. Looking between galaxies… @ Gregg & West

3. Stars in the intracluster medium • Diffuse light • Streams, filaments revealed by deep imaging • Resolved stellar populations • Giant red stars (HST detections) • Planetary nebulae (Narrow-band optical images; Spectroscopic confirmation) • ULXs, Supernovae Gregg & West, 1998 Arnaboldi et al., 2002 • Between 10 and 50% (20%) of the stellar mass in the ICM

4. Intergalactic HI clouds Merger NGC 3256 English, Koribalski & Freeman (2004)

5. Intergalactic molecular hydrogen IRAM 30m CO(1-0) Stephan’s quintet • More than 2.2 x 109 Mo of H2 outside galactic disks CO(1-0) HST/Gallagher et al., 2001;HI: Williams et al., 2002; CO:Lisenfeld et al., 2002

6. IRAM Pdb Lisenfeld et al., 2002 Lisenfeld et al., 2004 Intergalactic molecular hydrogen

7. MOSCA/Calar Alto Duc et al., 2004 Intergalactic ionized hydrogen

8. O Abundance (12=log(O/H) ) • Rather high metallicity -> not primordial; pre-enriched Intergalactic ionized hydrogen

9. Intergalactic star forming regions • Emission line regions detected in Ha images: • - Diffuse • Extended • “EL dots” • A range of star-formation rates: • 0.001 to 0.1 Mo / yr NGC 5291 Gavazzi et al., 2001 Bournaud et al., 2004 Ryan-Weber et al., 2004

10. Intergalactic recycling • HI -> H2 -> stars -> HII • HI • Old stars • Young stars

11. 106 - 108 Mo bound objects Super Star Clusters, Globular Clusters in tidal debris Weilbacher et al., 2002 Duc & Mirabel, 1995 Observations Hibbard & Barnes., 2004 Elmegreen et al., 1993 Simulations

12. “Tidal Dwarf Galaxies” HI • 109 Mo end-of-tail bound, gaseous accumulations

13. Kinematical signature • of “end-of-tail” projection effects Simulations • Streaming motions: a change in the velocity gradient before the end of the tail may reveal projection effects Bournaud et al., 2004

14. Kinematical signature • of “end-of-tail” projection effects Bournaud et al., 2004 Observations • Projection effects cannot account for all massive “end-of-tail” accumulations: some of them are real

15. Bournaud, Duc & Masset, 2003 Reproducing the structure of tidal tails Truncated DM halo Stars: 15kpc (50,000) Gas : 35 kpc (100,000) Dark matter halo: 45 kpc (100,000)

16. Bournaud, Duc & Masset, 2003 Extended DM halo Reproducing the structure of tidal tails Stars: 15kpc (50,000) Gas : 35 kpc (100,000) Dark matter halo: 150 kpc (100,000)

17. Duc, Bournaud & Masset, 2004 Reproducing the structure of tidal tails with high-resolution simulations • Stars: 106 particles • Gas : 106 particles • Dark matter halo: • 150 kpc (2 x 106) • Full N-body • (dissipation, self-gravity, • Star formation, feedback) • Vectorial computer • NEC-SX6 CCRT CEA Extended dark matter halo required

18. Reproducing the formation of Tidal Dwarf Galaxies Gas NGC 7252 Stars Duc, Bournaud & Masset, 2004 • M = 2 x109 Mo • M =109 Mo Observations N-body simulations

19. Simulations Observations

20. The formation of Tidal Dwarf Galaxies Simulations Duc, Bournaud & Masset, 2004 • without self-gravity • without gas dissipation • The proto-TDGs are still formed! • Their origin is fundamentally kinematical; only later self-gravity takes over, and the clouds collapse

21. The role of the extended dark matter halo Extended haloHalo tronqué Potential of an isothermal sphere Keplerian potential • According to the shape of the tidal field, matter from the external disk is either diluted or transported keeping its original surface brightness. This creates a density enhancement at the origin of the proto-TDGs

22. Radial excursions of tidal material with an extended/truncated halo Constant density Dilution Duc, Bournaud & Masset, 2004

23. The role of a dark matter baryonic component If existing in the disk, it should also be present in tidal tails, and in particular in TDGs NGC 5291 (optique + HI) Bournaud et al., 2004 • Internal kinematics of tidal tails and TDGs -> dynamical mass, compared to the luminous mass

24. Conclusions • All material available to fuel intergalactic star-formation: • Stripped, pre-enriched HI, transformed into H2 and stars • “Recycled” gravitationally bound objects formed out of tidal debris around interacting systems and mergers • Observations and simulations: two types of tidal objects, with different physical origins: • 106 - 108 Mo, distributed all along the tails, progenitors of Super Star Clusters and/or Globular Clusters, formed from growing local gravitational instabilities • 109 Mo, at or near the tip of tidal tails, progenitors of Tidal Dwarf Galaxies, with a kinematical origin, formed within extended Dark Matter haloes, according to a top-down scenario