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

2. Chania, August 2004 Intergalactic recycling: the formation of Tidal Dwarf Galaxies @ Gregg & West Looking between galaxies…

3. Chania, August 2004 Intergalactic recycling: the formation of Tidal Dwarf Galaxies Gregg & West, 1998 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 Stars in the intracluster medium Arnaboldi et al., 2002 Between 10 and 50% (20%) of the stellar mass in the ICM

4. Chania, August 2004 Intergalactic recycling: the formation of Tidal Dwarf Galaxies English, Koribalski & Freeman (2004) Intergalactic HI clouds Merger NGC 3256

5. Chania, August 2004 Intergalactic recycling: the formation of Tidal Dwarf Galaxies Stephan’s quintet HST/Gallagher et al., 2001;HI: Williams et al., 2002; CO:Lisenfeld et al., 2002 More than 2.2 x 10 9 Mo of H 2 outside galactic disks CO(1-0) Intergalactic molecular hydrogen IRAM 30m CO(1-0)

6. Chania, August 2004 Intergalactic recycling: the formation of Tidal Dwarf Galaxies Lisenfeld et al., 2002 IRAM Pdb Lisenfeld et al., 2004 Intergalactic molecular hydrogen

7. Chania, August 2004 Intergalactic recycling: the formation of Tidal Dwarf Galaxies Intergalactic ionized hydrogen MOSCA/Calar Alto Duc et al., 2004

8. Chania, August 2004 Intergalactic recycling: the formation of Tidal Dwarf Galaxies Intergalactic ionized hydrogen O Abundance (12=log(O/H) ) Rather high metallicity -> not primordial; pre-enriched

9. Chania, August 2004 Intergalactic recycling: the formation of Tidal Dwarf Galaxies NGC 5291 Emission line regions detected in H  images: - Diffuse - Extended - “EL dots” A range of star-formation rates: 0.001 to 0.1 Mo / yr Intergalactic star forming regions Bournaud et al., 2004 Gavazzi et al., 2001 Ryan-Weber et al., 2004

10. Chania, August 2004 Intergalactic recycling: the formation of Tidal Dwarf Galaxies Intergalactic recycling HI -> H2 -> stars -> HII HI Old stars Young stars

11. Chania, August 2004 Intergalactic recycling: the formation of Tidal Dwarf Galaxies Duc & Mirabel, 1995 Hibbard & Barnes., 2004 Observations Simulations Weilbacher et al., 2002 Elmegreen et al., 1993 Super Star Clusters, Globular Clusters in tidal debris 10 6 - 10 8 Mo bound objects

12. Chania, August 2004 Intergalactic recycling: the formation of Tidal Dwarf Galaxies “Tidal Dwarf Galaxies” 10 9 Mo end- of-tail bound, gaseous accumulations HI

13. Chania, August 2004 Intergalactic recycling: the formation of Tidal Dwarf Galaxies Kinematical signature Kinematical signature of “end-of-tail” projection effects Simulations Bournaud et al., 2004 Streaming motions: a change in the velocity gradient before the end of the tail may reveal projection effects

14. Chania, August 2004 Intergalactic recycling: the formation of Tidal Dwarf Galaxies Kinematical signature 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. Chania, August 2004 Intergalactic recycling: the formation of Tidal Dwarf Galaxies Stars: 15kpc (50,000) Gas : 35 kpc (100,000) Dark matter halo: 45 kpc (100,000) Bournaud, Duc & Masset, 2003 Truncated DM halo Reproducing the structure of tidal tails

16. Chania, August 2004 Intergalactic recycling: the formation of Tidal Dwarf Galaxies Bournaud, Duc & Masset, 2003 Stars: 15kpc (50,000) Gas : 35 kpc (100,000) Dark matter halo: 150 kpc (100,000) Extended DM halo Reproducing the structure of tidal tails

17. Chania, August 2004 Intergalactic recycling: the formation of Tidal Dwarf Galaxies Stars: 10 6 particles Gas : 10 6 particles Dark matter halo: 150 kpc (2 x 10 6 ) Full N-body (dissipation, self-gravity, Star formation, feedback) Vectorial computer NEC-SX6 CCRT CEA Duc, Bournaud & Masset, 2004 Reproducing the structure of tidal tails with high-resolution simulations

18. Chania, August 2004 Intergalactic recycling: the formation of Tidal Dwarf Galaxies N-body simulations Observations Gas Stars M =10 9 Mo M = 2 x10 9 Mo Reproducing the formation of Tidal Dwarf Galaxies Duc, Bournaud & Masset, 2004 NGC 7252

19. Chania, August 2004 Intergalactic recycling: the formation of Tidal Dwarf Galaxies Observations Simulations

20. Chania, August 2004 Intergalactic recycling: the formation of Tidal Dwarf Galaxies 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 Simulations The formation of Tidal Dwarf Galaxies Duc, Bournaud & Masset, 2004

21. Chania, August 2004 Intergalactic recycling: the formation of Tidal Dwarf Galaxies 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 Extended halo Halo tronqué Potential of an isothermal sphere Keplerian potential The role of the extended dark matter halo

22. Chania, August 2004 Intergalactic recycling: the formation of Tidal Dwarf Galaxies Radial excursions of tidal material with an extended/truncated halo Dilution Constant density Duc, Bournaud & Masset, 2004

23. Chania, August 2004 Intergalactic recycling: the formation of Tidal Dwarf Galaxies Internal kinematics of tidal tails and TDGs -> dynamical mass, compared to the luminous mass NGC 5291 (optique + HI) Bournaud et al., 2004 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

24. Chania, August 2004 Intergalactic recycling: the formation of Tidal Dwarf Galaxies Conclusions All material available to fuel intergalactic star-formation: Stripped, pre-enriched HI, transformed into H 2 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: 10 6 - 10 8 Mo, distributed all along the tails, progenitors of Super Star Clusters and/or Globular Clusters, formed from growing local gravitational instabilities 10 9 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