1. Steve Boudreault ASTRO DEBATA Tuesday 24 th of February 2009 The formation of brown dwarfs as revealed by the mass function of IC 2391 Collaborators (MPIA) : Coryn Bailer-Jones Reinhard Mundt Thomas Henning Wei Wang Mario Gennaro (external) : José Caballero, U of Mardid IAC, Canary Islands Ray Jayawardhana, U of Toronto Postdoctoral researcher at the Max-Planck-Institut für Astronomie Heidelberg, Germany

2. Theoretical Background Photometric Survey Spectroscopic Follow-up Future Work Today, I will talk about …

3. Steve Boudreault ASTRO DEBATA, 24.02.2009 3 Theoretical Background Photometric Survey Spectroscopic Follow-up Future Work ⇨ Compression & fragmentation of molecular cloud (star-like)‏ ⇨ Formation in circumstellar disk (planet-like) ⇨ Interruption of star-like accretion (ejection, photoevaporation)‏ Theoretical Background : different formation mechanisms of brown dwarfs How to form brown dwarfs ?

4. Steve Boudreault ASTRO DEBATA, 24.02.2009 4 Theoretical Background Photometric Survey Spectroscopic Follow-up Future Work ⇨ Compression & fragmentation of molecular cloud (star-like)‏ ⇨ Formation in circumstellar disk (planet-like) ⇨ Interruption of star-like accretion (ejection, photoevaporation)‏ Theoretical Background : different formation mechanisms of brown dwarfs Distinction between these scenarios : presence / distribution of binaries presence / distribution of binaries kinematics / spatial distribution kinematics / spatial distribution presence of circumstellar disk presence of circumstellar disk Mass function (MF) Mass function (MF) Grether & Lineweaver ( 2006 )P < 5 yr (≤ 3AU for BD) & D ≤ 50pc

5. Steve Boudreault ASTRO DEBATA, 24.02.2009 5 Theoretical Background Photometric Survey Spectroscopic Follow-up Future Work ⇨ Compression & fragmentation of molecular cloud (star-like)‏ ⇨ Formation in circumstellar disk (planet-like) ⇨ Interruption of star-like accretion (ejection, photoevaporation)‏ Theoretical Background : different formation mechanisms of brown dwarfs Distinction between these scenarios : presence / distribution of binaries presence / distribution of binaries kinematics / spatial distribution kinematics / spatial distribution presence of circumstellar disk presence of circumstellar disk Mass function (MF) Mass function (MF) ( Taurus star-forming region ) Kumar & Schmeja (2007)

6. Steve Boudreault ASTRO DEBATA, 24.02.2009 6 Theoretical Background Photometric Survey Spectroscopic Follow-up Future Work ⇨ Compression & fragmentation of molecular cloud (star-like)‏ ⇨ Formation in circumstellar disk (planet-like) ⇨ Interruption of star-like accretion (ejection, photoevaporation)‏ Theoretical Background : different formation mechanisms of brown dwarfs Distinction between these scenarios : presence / distribution of binaries presence / distribution of binaries kinematics / spatial distribution kinematics / spatial distribution presence of circumstellar disk presence of circumstellar disk Mass function (MF) Mass function (MF) M9.5 M ~ 15 M J

7. Steve Boudreault ASTRO DEBATA, 24.02.2009 7 Theoretical Background Photometric Survey Spectroscopic Follow-up Future Work ⇨ Compression & fragmentation of molecular cloud (star-like)‏ ⇨ Formation in circumstellar disk (planet-like) ⇨ Interruption of star-like accretion (ejection, photoevaporation)‏ Theoretical Background : different formation mechanisms of brown dwarfs Distinction between these scenarios : presence / distribution of binaries presence / distribution of binaries kinematics / spatial distribution kinematics / spatial distribution presence of circumstellar disk presence of circumstellar disk Mass function (MF) Mass function (MF) Muench et al. (2002) Bouvier et al. (2008) Briceño et al. (2002)

8. Steve Boudreault ASTRO DEBATA, 24.02.2009 8 Theoretical Background Photometric Survey Spectroscopic Follow-up Future Work ⇨ Compression & fragmentation of molecular cloud (star-like)‏ ⇨ Formation in circumstellar disk (planet-like) ⇨ Interruption of star-like accretion (ejection, photoevaporation)‏ Theoretical Background : different formation mechanisms of brown dwarfs Distinction between these scenarios : presence / distribution of binaries presence / distribution of binaries kinematics / spatial distribution kinematics / spatial distribution presence of circumstellar disk presence of circumstellar disk Mass function (MF) Mass function (MF) Bate & Bonnell, 2005, MNRAS, 356, 1201 Numerical simulation of compression & fragmentation of a molecular cloud ⇨ BDs form via the ejection scenario ⇨ BDs form via the ejection scenario Bonnell et al. 2008, MNRAS, 389, 1556 Numerical simulation of compression & fragmentation of a molecular cloud ⇨ BDs form like stars in high gas density ⇨ BDs form like stars in high gas density Luhman et al. 2007, Protostar and Planets V astro-ph/06085461 Review of observational signatures ⇨ Common formation for BDs and stars

9. Steve Boudreault ASTRO DEBATA, 24.02.2009 9 ⇨ Compression & fragmentation of molecular cloud (star-like)‏ ⇨ Formation in circumstellar disk (planet-like) ⇨ Interruption of star-like accretion (ejection, photoevaporation)‏ Theoretical Background : different formation mechanisms of brown dwarfs Distinction between these scenarios : presence / distribution of binaries presence / distribution of binaries kinematics / spatial distribution kinematics / spatial distribution presence of circumstellar disk presence of circumstellar disk Mass function (MF) Mass function (MF) For our project … ⇦ Theoretical Background Photometric Survey Spectroscopic Follow-up Future Work

10. Steve Boudreault ASTRO DEBATA, 24.02.2009 10 Theoretical Background Photometric Survey Spectroscopic Follow-up Future Work Photometric Survey : determination of the mass function for very low mass stars and brown dwarfs population in IC 2391 and look for radial dependence IC 2391 is an interesting target because … objects in clusters have same metallicity and are coeval objects in clusters have same metallicity and are coeval near : distance is 146pc ( Robichon et al., 1999 ) near : distance is 146pc ( Robichon et al., 1999 ) age of 50Myr ( Barrado y Navascués et al, 2004) age of 50Myr ( Barrado y Navascués et al, 2004) ⇨ not too young ( extinction due to molecular gaz ) ⇨ not too young ( extinction due to molecular gaz ) ⇨ not too old ( relaxation time is 104.9Myr, optical data ) low reddening : E(B-V) = 0.01 ( Randoch et al., 2001 ) previous study of MF : completness limit of 0.072M  no radial study of IC 2391 yet IC 2391 Why the open cluster IC 2391 ?

11. Steve Boudreault ASTRO DEBATA, 24.02.2009 11 Theoretical Background Photometric Survey Spectroscopic Follow-up Future Work Photometric Survey : determination of the mass function for very low mass stars and brown dwarfs population in IC 2391 and look for radial dependence 35 ESO/WFI fields of 34’x33’ ( ~ 10.9 deg 2 ) Fields chosen to … ⇨ avoid bright stars ⇨ avoid bright stars ⇨ avoid MF gradient due to ⇨ avoid MF gradient due to low galactic latitude b~-6º low galactic latitude b~-6º

12. Steve Boudreault ASTRO DEBATA, 24.02.2009 12 Theoretical Background Photometric Survey Spectroscopic Follow-up Future Work Photometric Survey : determination of the mass function for very low mass stars and brown dwarfs population in IC 2391 and look for radial dependence Wide bands R c and J Medium bands at 770, 815, 856 and 914 nm ⇨ ESO/WFI (optical data) ⇨ CTIO/CPAPIR (IR data) Those bands were chosen … ⇨ to sample spectra of M and L-dwarfs ⇨ to minimize Earth-sky background

13. Steve Boudreault ASTRO DEBATA, 24.02.2009 13 Theoretical Background Photometric Survey Spectroscopic Follow-up Future Work Photometric Survey : determination of the mass function for very low mass stars and brown dwarfs population in IC 2391 and look for radial dependence 1st selection : - Color-magnitude diagram - Isochrones 2nd selection : - Color-color diagram - Isochrones - Red giant colors ( Hauschildt et al. 1999 ) - Color VS T eff for G, K, M and L dwarfs

14. Steve Boudreault ASTRO DEBATA, 24.02.2009 14 Theoretical Background Photometric Survey Spectroscopic Follow-up Future Work Photometric Survey : determination of the mass function for very low mass stars and brown dwarfs population in IC 2391 and look for radial dependence 3rd selection : - Astrometry (from our 8 years baseline) (from our 8 years baseline) 4th selection : - M [obs] VS M [model] ( from Teff and mass ) - Errors on age and distance of IC 2391 - Unresolved binaries

15. Steve Boudreault ASTRO DEBATA, 24.02.2009 15 Theoretical Background Photometric Survey Spectroscopic Follow-up Future Work Photometric Survey : determination of the mass function for very low mass stars and brown dwarfs population in IC 2391 and look for radial dependence ⇨ Major : radial variation 0.15 M  < M < 0.5 M  ⇨ Major : no radial variation M ≤ 0.11 M  ⇨ Minor : long spectral baseline = less M-dwarf contaminants ⇨ Minor : medium band = less M-giant contaminants ⇨ Minor : colour variation with E ( B – V ) ⇨ Major : radial variation 0.15 M  < M < 0.5 M  ⇨ Major : no radial variation M ≤ 0.11 M  ⇨ Minor : long spectral baseline = less M-dwarf contaminants ⇨ Minor : medium band = less M-giant contaminants ⇨ Minor : colour variation with E ( B – V )

16. Steve Boudreault ASTRO DEBATA, 24.02.2009 16 Theoretical Background Photometric Survey Spectroscopic Follow-up Future Work Photometric Survey : determination of the mass function for very low mass stars and brown dwarfs population in IC 2391 and look for radial dependence ⇨ Major : radial variation 0.15 M  < M < 0.5 M  ⇨ Major : no radial variation M ≤ 0.11 M  ⇨ Minor : long spectral baseline = less M-dwarf contaminants ⇨ Minor : medium band = less M-giant contaminants ⇨ Minor : colour variation with E ( B – V ) ⇨ Major : radial variation 0.15 M  < M < 0.5 M  ⇨ Major : no radial variation M ≤ 0.11 M  ⇨ Minor : long spectral baseline = less M-dwarf contaminants ⇨ Minor : medium band = less M-giant contaminants ⇨ Minor : colour variation with E ( B – V )

17. Steve Boudreault ASTRO DEBATA, 24.02.2009 17 Theoretical Background Photometric Survey Spectroscopic Follow-up Future Work Photometric Survey : determination of the mass function for very low mass stars and brown dwarfs population in IC 2391 and look for radial dependence ⇨ Major : radial variation 0.15 M  < M < 0.5 M  ⇨ Major : no radial variation M ≤ 0.11 M  ⇨ Minor : long spectral baseline = less M-dwarf contaminants ⇨ Minor : medium band = less M-giant contaminants ⇨ Minor : colour variation with E ( B – V ) ⇨ Major : radial variation 0.15 M  < M < 0.5 M  ⇨ Major : no radial variation M ≤ 0.11 M  ⇨ Minor : long spectral baseline = less M-dwarf contaminants ⇨ Minor : medium band = less M-giant contaminants ⇨ Minor : colour variation with E ( B – V ) Barrado y Navasqués et al. (2004)

18. Steve Boudreault ASTRO DEBATA, 24.02.2009 18 Theoretical Background Photometric Survey Spectroscopic Follow-up Future Work Photometric Survey : determination of the mass function for very low mass stars and brown dwarfs population in IC 2391 and look for radial dependence ⇨ Major : radial variation 0.15 M  < M < 0.5 M  ⇨ Major : no radial variation M ≤ 0.11 M  ⇨ Minor : long spectral baseline = less M-dwarf contaminants ⇨ Minor : medium band = less M-giant contaminants ⇨ Minor : colour variation with E ( B – V ) ⇨ Major : radial variation 0.15 M  < M < 0.5 M  ⇨ Major : no radial variation M ≤ 0.11 M  ⇨ Minor : long spectral baseline = less M-dwarf contaminants ⇨ Minor : medium band = less M-giant contaminants ⇨ Minor : colour variation with E ( B – V ) Ο Jeffries et al. (2004) Δ Naylor et al. (2002)

19. Steve Boudreault ASTRO DEBATA, 24.02.2009 19 Theoretical Background Photometric Survey Spectroscopic Follow-up Future Work Photometric Survey : determination of the mass function for very low mass stars and brown dwarfs population in IC 2391 and look for radial dependence ⇨ Major : radial variation 0.15 M  < M < 0.5 M  ⇨ Major : no radial variation M ≤ 0.11 M  ⇨ Minor : long spectral baseline = less M-dwarf contaminants ⇨ Minor : medium band = less M-giant contaminants ⇨ Minor : colour variation with E ( B – V ) ⇨ Major : radial variation 0.15 M  < M < 0.5 M  ⇨ Major : no radial variation M ≤ 0.11 M  ⇨ Minor : long spectral baseline = less M-dwarf contaminants ⇨ Minor : medium band = less M-giant contaminants ⇨ Minor : colour variation with E ( B – V ) Schlegel et al. (1998)

20. Steve Boudreault ASTRO DEBATA, 24.02.2009 20 Theoretical Background Photometric Survey Spectroscopic Follow-up Future Work Spectroscopic Follow-up : Spectroscopic Follow-up : improve candidate selection and spectral type determination CTIO / HYDRA 2 Nights in January 2007 ⇨ 1st lost (bad weather) ⇨ 2hrs lost (technical) ⇨ I c ~18 ( 45 M J ) FINALLY WE HAD 4HRS !! ( out of 12hrs awarded )

21. Steve Boudreault ASTRO DEBATA, 24.02.2009 21 Theoretical Background Photometric Survey Spectroscopic Follow-up Future Work Spectroscopic Follow-up : Spectroscopic Follow-up : improve candidate selection and spectral type determination ⇨ measurement of EW ⇨ SpT determination ⇨ 68 % contamination ⇨ MF ??? … but no red giants.

22. Steve Boudreault ASTRO DEBATA, 24.02.2009 22 Theoretical Background Photometric Survey Spectroscopic Follow-up Future Work Spectroscopic Follow-up : Spectroscopic Follow-up : improve candidate selection and spectral type determination

23. Steve Boudreault ASTRO DEBATA, 24.02.2009 23 Theoretical Background Photometric Survey Spectroscopic Follow-up Future Work Spectroscopic Follow-up : Spectroscopic Follow-up : improve candidate selection and spectral type determination FROM PHOTOMETRY : Teff = 2791K M=0.058M  815/20=17.54 V r = 16.25±6.59 km/s

24. Steve Boudreault ASTRO DEBATA, 24.02.2009 24 Theoretical Background Photometric Survey Spectroscopic Follow-up Future Work Future Work : Future Work : follow-up on brown dwarfs candidates and survey on other open clusters ⇨ Other clusters : Praesepe (WFI, O2K, LBTC, WFC, ~45M J ) Coma Ber (O2K, …) Alessi 5 & ASCC 24 (WFI + O2K, ~20M J ) ⇨ VLT/VIMOS for IC2391 (April 2008 --- February 2009) What’s next ? ⇨ NTT/SofI (J & Ks) for IC2391 (deep fields) ⇨ Numerical simulation … evolution of MF of cluster with σ v

25. Steve Boudreault ASTRO DEBATA, 24.02.2009 25 CONCLUSIONS AND REVIEW We are interested in the formation and evolution of BDs population ⇨ Survey in open cluster to obtain MF of VLMS and BDs Photometric survey of IC 2391 ⇨ MF shows no variation on the BDs and VLMS regime ⇨ if formed by ejection, velocity BDs = velocity VLMS ⇨ if velocity BDs > velocity VLMS and ejection give high velocity for BDs, then ejection not dominant formation process NEEDED However important contamination : spectroscopic follow-up NEEDED ⇨ Analyses of preliminary spectroscopic follow-up : 32% real members, no red giants and 7 new brown dwarfs … and additional data from VLT next spring Still a lot of work and projects … FROM PHOTOMETRY : Teff = 2791K M=0.058M  815/20=17.54 V r = 16.25±6.59 km/s