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Observational Frontiers in the Multiplicity of Young Stars

Observational Frontiers in the Multiplicity of Young Stars. Karl E. Haisch Jr. (UVSC), Mary Barsony (SFSU) Gaspard Duch ê ne (Grenoble Obs.) Eduardo Delgado-Donate (Stockholm Obs.) Thomas P. Greene (NASA ARC), Laurent Loinard (UNAM) Luis F. Rodr í guez (UNAM), Steve Stahler (UC Berkeley).

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Observational Frontiers in the Multiplicity of Young Stars

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  1. Observational Frontiers in the Multiplicity of Young Stars Karl E. Haisch Jr. (UVSC), Mary Barsony (SFSU) Gaspard Duchêne (Grenoble Obs.) Eduardo Delgado-Donate (Stockholm Obs.) Thomas P. Greene (NASA ARC), Laurent Loinard (UNAM) Luis F. Rodríguez (UNAM), Steve Stahler (UC Berkeley)

  2. Presentation Outline • Why study young multiple systems? • T Tauri multiple systems • Embedded multiple systems • Summary Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  3. Importance of Multiple Systems • Multiple stellar systems are ubiquitous Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  4. Importance of Multiple Systems • Multiple stellar systems are ubiquitous • They result from core fragmentation and later interact with stars and gas Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  5. Importance of Multiple Systems • Multiple stellar systems are ubiquitous • They result from core fragmentation and later interact with stars and gas • Their statistical properties depend on the physical processes at play Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  6. Importance of Multiple Systems • Multiple stellar systems are ubiquitous • They result from core fragmentation and later interact with stars and gas • Their statistical properties depend on the physical processes at play Multiple systems are a probe of the star formation process Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  7. Early Multiplicity Surveys • Surveys of young stellar populations were conducted in the 1990s Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  8. Early Multiplicity Surveys • Surveys of young stellar populations were conducted in the 1990s • Very high multiplicity in all of them, in some cases even higher than field stars Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  9. Early Multiplicity Surveys • Surveys of young stellar populations were conducted in the 1990s • Very high multiplicity in all of them, in some cases even higher than field stars • Environment-dependent behavior (clusters vs. “T associations”) Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  10. Early Multiplicity Surveys • Surveys of young stellar populations were conducted in the 1990s • Very high multiplicity in all of them, in some cases even higher than field stars • Environment-dependent behavior (clusters vs. “T associations”) • Initial conditions or evolutionary effect? Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  11. Early Multiplicity Surveys • Surveys of young stellar populations were conducted in the 1990s • Very high multiplicity in all of them, in some cases even higher than field stars • Environment-dependent behavior (clusters vs. “T associations”) • Initial conditions or evolutionary effect? • Tremendous observational progress in this field Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  12. Low-Mass T Tauri Multiples • Early surveys primarily focused on 0.5-1.5 M T Tauri stars Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  13. Low-Mass T Tauri Multiples • Early surveys primarily focused on 0.5-1.5 M T Tauri stars • Sampling M<0.5 M objects is critical to constrain models Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  14. Low-Mass T Tauri Multiples • Early surveys primarily focused on 0.5-1.5 M T Tauri stars • Sampling M<0.5 M objects is critical to constrain models • Low-mass stellar multiples in the Taurus cloud are • much tighter (sep. < 60 AU) • more equal mass (q > 0.7) • slightly less frequent proj MB / MA Multiplicity White et al. (2006) Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  15. High-Order T Tauri Multiples • Among field stars, there are ~4 binaries for each triple/quadruple/… system Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  16. High-Order T Tauri Multiples • Among field stars, there are ~4 binaries for each triple/quadruple/… system • Targeting known binary T Tauri stars reveals at least as many triple systems Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  17. High-Order T Tauri Multiples • Among field stars, there are ~4 binaries for each triple/quadruple/… system • Targeting known binary T Tauri stars reveals at least as many triple systems • Even if considering only visual companions • Also true for tight spectroscopic binaries Koresko (2000), Melo (2003), Correia et al. (2006) Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  18. High-Order T Tauri Multiples • Among field stars, there are ~4 binaries for each triple/quadruple/… system • Targeting known binary T Tauri stars reveals at least as many triple systems • Even if considering only visual companions • Also true for tight spectroscopic binaries • Possible overabundance to be confirmed Koresko (2000), Melo (2003), Correia et al. (2006) Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  19. Probing Even Younger Systems • Core fragmentation occurs in ≤ 1 Myr, after that only star-star dynamics play Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  20. Probing Even Younger Systems • Core fragmentation occurs in ≤ 1 Myr, after that only star-star dynamics play • For an isolated core, the whole evolution is over by the T Tauri phase Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  21. Probing Even Younger Systems • Core fragmentation occurs in ≤ 1 Myr, after that only star-star dynamics play • For an isolated core, the whole evolution is over by the T Tauri phase • Need to search for youngest multiples • to constrain fragmentation “as it occurs” • to better test influence of environment Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  22. Probing Even Younger Systems • Core fragmentation occurs in ≤ 1 Myr, after that only star-star dynamics play • For an isolated core, the whole evolution is over by the T Tauri phase • Need to search for youngest multiples • to constrain fragmentation “as it occurs” • to better test influence of environment Multiplicity surveys of Class 0/I sources Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  23. Multiplicity of Embedded YSOs • First surveys conducted in radio domain Looney et al. (2000), Reipurth et al. (2002, 2004) Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  24. Multiplicity of Embedded YSOs • First surveys conducted in radio domain Looney et al. (2000), Reipurth et al. (2002, 2004) • Larger surveys later conducted in NIR Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  25. Multiplicity of Embedded YSOs • First surveys conducted in radio domain Looney et al. (2000), Reipurth et al. (2002, 2004) • Larger surveys later conducted in NIR • Similar findings: high multiplicity, similar to T Tauri stars’ excess 110-1400AU field Tau Oph Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  26. Multiplicity of Embedded YSOs • First surveys conducted in radio domain Looney et al. (2000), Reipurth et al. (2002, 2004) • Larger surveys later conducted in NIR • Similar findings: high multiplicity, similar to T Tauri stars’ excess • No difference between molecular clouds Haisch et al. (2002, 2004) Duchêne et al. (2004, 2006) 110-1400AU field Tau Oph Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  27. Sample of Nearby Dark Clouds CloudDistance (pc)# ObjectsRefs Perseus 320 9 1 Taurus-Auriga 140 11 2  Ophiuchus 125 37 3,4 Chamaeleon I, II 170 17 5,6,7 Serpens 310 19 8 93 • Ladd et al. (1993) • Kenyon & Hartmann (1995) • Wilking et al. (1989) • Greene et al. (1994) 5. & 6. Prusti et al. (1992a,b) 7. Persi et al. (1999) 8. Kass et al. (1999) Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  28. Near-IR Observations JHKL band Imaging Instruments: OSIRIS, NSFCAM Telescopes: Cerro Tololo Interamerican Observatory 4.0 m. NASA Infrared Telescope Facility 3.0 m Plate Scales: 0.161 arcsec/pix (CTIO) 0.148 arcsec/pix (IRTF) Sensitivity limits: mK,H,J = 18.5, 19.5, 20.5 (CTIO) mK,H,J = 19.0, 20.0, 21.0 (IRTF) Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  29. Multiple Companion Star Fractions CSF = B + 2T + 3Q / (S + B + T+Q) where S = # singles, B = # binaries, T = # triples, Q = # quadruples Restrictions: Separation = 100 – 2000 AU Mag difference K = 4  Class I/flat-spectrum CSF =18%  4%  T Tauri Star CSF for same regions = 19%  3%  CSF for solar-type and M-dwarf main sequence stars =11%  3% • Similar results have been found in adaptive optics survey of 44 Class I YSOs by Duchene et al. (2006), which covers a separation range of 36 - 1400 AU. Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  30. Multiplicity of Embedded YSOs • Core fragmentation independent on large physical scales; only sensitive to small-scale physics which may be very similar in all molecular clouds • No dense association of  5 protostars - If cores fragment into that many independent seeds, they must decay into unbound stable configurations within a very short timescale, on order 105 years Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  31. Mid-IR Protostellar Binary Survey • Surveyed 64 sources from near-IR survey at N-band (10.3 m) • using Univ. of Arizona 8 - 25 m imager MIRAC3/BLINC at the • Magellan 6.5 m telescope on Las Campanas, Chile, and JPL • 8 - 25 µm imager MIRLIN at Palomar Observatory in California. - MIRAC Plate scale = 0.123 arcsec/pix  field of view 15.7’’ x 15.7’’ - MIRLIN Plate scale = 0.150 arcsec/pix  field of view 19.2’’ x 19.2’’ • Detected 45/48 (94%) of the single sources, 16/16 (100%) of • the primary components, and 12/16 (75%) of the • secondary/triple components of the binary/multiple objects • surveyed. Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  32. Young Stellar ObjectSpectral Energy Distributions Class I ( > 0.3) Flat Spectrum (0.3 >   -0.3), Class II (-0.3 >   -1.6) Class III ( < -1.6) Spectral Index  = dlog(F)/dlog() e.g. Adams, Lada & Shu (1987) Adams, Shu & Lada. (1988) Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  33. JHKL Color-Color Diagram for Multiples Haisch et al. (2006) Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  34. KLN Color-Color Diagram for Multiples Haisch et al. (2006) Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  35. Multiple protostar evolutionary status • Color-color diagrams generally indicate clear progression from Class I  FS  Class II • Extinction estimates, AV, similar for individual binary/multiple components • ISO-Cha I 97 is a binary star, in which the secondary has very steep spectral index   3.9; member of very rare YSO class Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  36. Interesting Case: ISO-Cha I 97 E Sep’n = 2.95 arcsec; PA = 72.6 deg. N Secondary has spectral index  ≥ 3.9! Haisch et al. (2004, 2006) Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  37.  Ophiuchi Binary WL 1  = -0.5 N  = -0.7 E Both Class II Sep’n = 0.82 arcsec; PA = 321 deg. Haisch et al. (2002) Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  38.  Ophiuchi binary L1689 IRS 5 N E N is flat-spectrum S is Class II Sep’n = 2.92 arcsec; PA = 240 deg. Haisch et al. (2002, 2004) Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  39. Comparison of Primary/Secondary Spectral Indices for Class I YSOs Haisch et al. (2006) Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  40. Comparison of Primary/Secondary Spectral Indices for Class II YSOs Haisch et al. (2006) Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  41. Implications There appears to be a higher proportion of mixed Class I/Flat-Spectrum systems (65-80%) than that found in mixed Class II systems (25-40%) Given the low likelihood of misclassification of Class I and Class II YSOs, this demonstrates that the envelopes of Class I/Flat-Spectrum systems are rapidly evolving during this phase of evolution, although they still may be coeval. Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  42. Some Peculiar Embedded YSOs • Surveys revealed “mixed” systems with embedded and non-embedded objects • non-coeval objects in bound systems? Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  43. Some Peculiar Embedded YSOs • Surveys revealed “mixed” systems with embedded and non-embedded objects • non-coeval objects in bound systems? • What do they tell us exactly? • Inadequate Class 0-I-II-III sequence Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  44. Some Peculiar Embedded YSOs • Surveys revealed “mixed” systems with embedded and non-embedded objects • non-coeval objects in bound systems? • What do they tell us exactly? • Inadequate Class 0-I-II-III sequence • Abrupt evolutionary changes (disruptions?) • Misclassification due to peculiar geometry Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  45. Some Peculiar Embedded YSOs • Surveys revealed “mixed” systems with embedded and non-embedded objects • non-coeval objects in bound systems? • What do they tell us exactly? • Inadequate Class 0-I-II-III sequence • Abrupt evolutionary changes (disruptions?) • Misclassification due to peculiar geometry • Dedicated follow-up studies needed Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  46. The Earliest Dynamical Masses • Orbital motion of embedded binaries is achievable with VL(B)A observations Loinard (2002), Loinard et al. (2002) Curiel et al. (2003), Rodríguez et al. (2003) Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  47. The Earliest Dynamical Masses • Orbital motion of embedded binaries is achievable with VL(B)A observations Comparable mass to T Tauri systems Loinard (2002), Loinard et al. (2002) Curiel et al. (2003), Rodríguez et al. (2003) Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  48. Conclusions Protostellar companion star fraction 2 - 2.5x T Tauri and Main Sequence fraction. No evidence that any star-forming region presents a significantly higher/lower multiplicity rate. No significant evolution of the multiple system population found within the ≤ 1 Myr timescale during which protostars evolve into optically bright T Tauri stars. • No dense associations of 5 or more protostars found on spatial scales ≤ 2000 AU. Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

  49. Conclusions (cont.) Extinction estimates, AV, are generally similar for individual binary/multiple components. Many of the individual component SEDs display mixed pairings which is not consistent with what one typically finds for T Tauri stars. ISO-Cha I 97 is a binary star, in which the secondary has a very steep spectral index of a ≥ 3.9. Member of a rare class of YSO i.e., those with a > 3. Only 3 such objects previously known. Observational Frontiers In The Multiplicity Of Young Stars From Stars to Planets - April 12, 2007

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