1. Disks in the Sub-Stellar Regime Ray Jayawardhana University of Toronto

2. Context and Motivation * Brown dwarfs occupy the mass range between stars and planets: ~75 -- ~12 M Jupiter (and below) * Found both as companions to stars and as free-floating objects (vast majority so far) * At ages of a few Myrs, their T eff ~ 3000-1500K (~M6-mid L)

3. Key Observational Question: Do Young Sub-Stellar Objects undergo a T Tauri-like Phase? Jets/Outflows from Hartmann (1998)

4. Investigating Young Brown Dwarfs: A Multi-Faceted Approach * Measurements of Disk Excess * Disk Mass and Radius Estimates from mm Fluxes * Search for Spectroscopic Signatures of Accretion * Looking for Evidence of Jets/Outflows --------------------------------- * Binary frequency and properties * Determination of Sub-Stellar Physical Properties (Mohanty et al. 2004a; Mohanty, Jayawardhana & Basri 2004b) * Studies of Angular Momentum Evolution (v sin i, photometric periods) and Activity (H , X-rays, radio) (e.g., Stelzer et al. 2006; Osten & Jayawardhana 2006)

5. Disk Excess Measurements Sample 50+ objects with known spectral types later than M5 in nearby star-forming regions Observations JHKL’ photometry at VLT, Keck and IRTF, plus 2MASS K-L’ is a more reliable measure of disk fractions: less susceptible to geometric effects, smaller extinction corrections, easily measurable above photosphere Jayawardhana, Ardila, Stelzer & Haisch (2003) also see Comeron et al. (1998); Natta & Testi (2001); Natta et al. (2002); Liu et al. (2003)

6. Mohanty, Jayawardhana, Natta, et al. (2004) Flared disks in GY 310 and GY 11 Inner disk holes of a few (sub-)stellar radii in all three Possible silicate feature in GY 310 Constraining the Disk Geometry: Ground-based Mid-IR Observations

7. Scholz, Jayawardhana, Wood & Meeus Constraining Disk Geometry and Evolution: Spitzer Mid-IR Observations -disk flaring -inner hole size -grain growth and/or processing ~20 BDs in Taurus @ ~2 Myr ~30 BDs in Upper Sco @ ~5 Myr

8. Apai et al. (2005) Grain Processing in Brown Dwarf Disks

9. Scholz, Jayawardhana, Wood & Meeus Evidence for dust settling and inner holes? Taurus Upper Sco

10. Zooming in on H  Disk Fraction among Upper Sco BDs (~5 Myr) Scholz, Jayawardhana, Wood & Meeus

11. Masses of Brown Dwarf Disks IRAM 1.3mm survey of 20 BDs in Taurus 6 detected with disk masses ~ 0.7 - 2.5 M Jupiter 14 not detected implying disk masses < 0.6 M Jupiter (3  Disk masses range from < ~0.7% -- ~5% of BD mass Scholz, Jayawardhana & Wood (2006) Two BDs detected at mm by Pascucci et al. (2003) & Klein et al. (2003)

12. Ratio of Disk/Object Mass vs. Object Mass Scholz, Jayawardhana & Wood (2006)

13. Minimum Disk Radii at least 25% with r > 10 AU (in contrast to Bate et al. 2002 prediction of ~5% with r > 10 AU) Scholz, Jayawardhana & Wood (2006)

14. Spectroscopic Signatures of Accretion Sample Objects with known spectral types later than M5 in Upper Scorpius,  Ophiuchus, IC 348, Taurus, Chamaeleon I, and TW Hydrae Total ~ 82 (!), including 55 brown dwarfs (M6 and later) Observations High-resolution optical spectra at Keck and Magellan R~33,000 (HIRES), R~20,000 (MIKE) H  line profiles in high-resolution spectra is a good diagnostic of accretion (also OI, HeI, CaII in some cases)

15. H  Criterion for Accretion * H  EW > 10A are usually categorized as CTTS * But this threshold value varies with spectral type H  line width at 10% of the peak may be a better indicator * Nearly free-falling flow between disk inner edge and star * For brown dwarfs at a few Myr, adopted accretion threshold: ~200 km/s (+ other diagnostics) (White & Basri 2003; Jayawardhana, Mohanty, & Basri 2003) Natta et al. (2004) Accretion Rate vs. H  10% Width

16. Jayawardhana, Mohanty & Basri (2002, 2003); Mohanty, Jayawardhana & Basri (2005) also see White & Basri (2003); Muzerolle et al. (2003) H  line profiles of some accretors

17. Jayawardhana, Mohanty & Basri (2002) H  line profiles for Upper Sco (~5 Myr)

18. Mohanty, Jayawardhana & Barrado y Navascués (2003) Mohanty, Jayawardhana & Basri (2005) The Interesting Case of the 8-Myr-old Brown Dwarf 2MASS 1207-3932 in the TW Hydrae Association Accretion and outflow in BDs can persist for up to ~8 Myrs inner disk hole Jayawardhana et al.(2003); Sterzik et al. (2004) on-going accretion and possible wind?

19. Mohanty, Jayawardhana & Basri (2005) also see Natta et al. (2004); Muzerolle et al. (2005) Accretion Rate vs. (Sub-)Stellar Mass

20. Fraction of Accretors RegionFractionEst. Age  Oph6/9< 1 Myr Taurus12/30~1 Myr IC 348& Cha I10/32~2 Myr Upper Sco1/20~5 Myr TW Hya1/3 ~8 Myr In Taurus, Cha I and Upper Sco, several objects with K-L’ excess do not show accretion-like H  profiles Disks persist after accretion rates have dropped? 2MASS1207-3932 in TWA: accretion and mid-IR excess, no L’ excess

21. Fraction of Accretors as a Function of Age: Comparison with higher mass stars Mohanty, Jayawardhana & Basri (2005) Blue squares: K0- M4 stars using BM03 Red circles: VLM objects using BM03 Black triangles: VLM objects with our high-res. analysis

22. Rotation-Disk Connection? Basri, Mohanty & Jayawardhana, in prep.

23. Rotation-Disk Connection? Scholz & Eisloffel (2004)

24. Fernandez & Comeron (2001); Barrado y Navascués, Mohanty & Jayawardhana (2004) Outflows in the VLM Domain? LS RCrA 1Cha II-C41 Barrado y Navascués, & Jayawardhana (2004)

25. Whelan et al. (2005) Outflows in the VLM Domain?

26. Summary * A large fraction of young sub-stellar objects harbor K-L’ excess consistent with optically thick dusty disks * Mid-IR and mm observations suggest a range of disk geometries and dust properties similar to those of TTS -Possible evidence of dust settling and inner holes by ~5 Myr -Disk masses 10 AU * Many brown dwarfs show signs of accretion at very young ages * Disks appear to persist after accretion rates have dropped below measurable levels (e.g., Upper Sco) * Inner disk lifetimes of brown dwarfs do not appear to be vastly different from those of T Tauri stars * Tantalizing evidence of outflows/winds in a number of objects Compelling Evidence for a T Tauri Phase in Young Sub-Stellar Objects

27. Planetary Mass Companion to a Nearby Young Brown Dwarf Chauvin et al. (2004, 2005)

28. Planetary Mass Companion to a Nearby Young Brown Dwarf Mohanty, Jayawardhana, Huelamo & Mamajek (2006) Companion mass ~ 8x Jupiter Companion T eff ~ 1600 K

29. Mohanty, Jayawardhana, Huelamo & Mamajek (2006)

30. A disk around the secondary as well?

31. Other Planetary Mass Objects with Disks? Using Spitzer, Allers et al. (2006) identified 6 candidates in nearby SFRs with inferred masses of ~6-15 M Jupiter and mid-IR excesses possibly from dusty disks also see Luhman et al. (2006)

32. Optical spectra from VLT and NTT Two ~5-10 M J One ~10-20 M J Two ~30-40 M J One likely background source! Jayawardhana & Ivanov (2006)

33. Zooming in on H 

34. © Don Dixon / Scientific American