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Multiplicity Among Embedded Protostars: Insights from Toronto Conference 2007

Explore the intricate world of star formation multiplicity at the Toronto conference in 2007. Delve into the complexities of scaled mass functions, environmental influences, and the physics of core fragmentation. Gain invaluable insights into the early evolution of stellar systems and the implications for ongoing research. Discover the latest findings on high multiplicity rates, intriguing system properties, and the universal scenario driving star formation dynamics.

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Multiplicity Among Embedded Protostars: Insights from Toronto Conference 2007

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  1. Multiplicity among embedded protostars Gaspard Duchêne (Grenoble) J. Bouvier, S. Bontemps, P. André, F. Motte, A. Djupvik, A. Ghez Multiplicity in Star Formation - Toronto - 16-18 May 2007

  2. General background • Multiplicity well studied for ages  106 yrs Large excess in some young populations Scaled MF from VB surveys Apparent dependence on environment T Tauri stars open clusters field Multiplicity in Star Formation - Toronto - 16-18 May 2007

  3. General background • Interpretation still ambiguous: Scaled MF from VB surveys ? Multiplicity in Star Formation - Toronto - 16-18 May 2007

  4. General background • Interpretation still ambiguous: Tracer of different initial states ? Scaled MF from VB surveys  Physics of core fragmentation Higher cloud mass Multiplicity in Star Formation - Toronto - 16-18 May 2007

  5. General background • Interpretation still ambiguous: Tracer of different initial states ? Scaled MF from VB surveys  Physics of core fragmentation Denser clusters Tracer of a different early evolution ? Stellar dynamics Multiplicity in Star Formation - Toronto - 16-18 May 2007

  6. General background • Need to survey even younger systems: • Embedded protostars ! Class 0 age ~ 104 yrs, radio Scaled MF from VB surveys ? Class I age ~ 105 yrs, IR Reipurth (2000) 80-85% MF Multiplicity in Star Formation - Toronto - 16-18 May 2007

  7. This work : basic presentation • Objective: survey of protostars with deep, high resolution, NIR imaging • Several SFRs • Taurus vs. Orion • Focus on • Class I • Flat Spectrum (FS) FS Class I Kaas et al. (2004) Multiplicity in Star Formation - Toronto - 16-18 May 2007

  8. This work : basic presentation • Observations: • Seeing-limited: CFHT-IR (0.6”) JHK • Diffraction-limited: VLT-NACO (0.07”) HKL’ CFHT-IR VLT-NACO ~7 mag ~7 mag 1’’ 10’’ 0.1’’ 1’’ 10’’ Duchene et al. (2007) Duchene et al. (2004) Multiplicity in Star Formation - Toronto - 16-18 May 2007

  9. Additional sample • When available, we also added older HST/NICMOS images to our survey • Somewhat poorer resolution (0.15’’) • Higher PSF stability • Higher sensitivity (fainter targets) 0.24’’ Padgett et al. (1999) Multiplicity in Star Formation - Toronto - 16-18 May 2007

  10. This work : sample • Overview of our sample: Multiplicity in Star Formation - Toronto - 16-18 May 2007

  11. This work : sample • Sample represents ~40% of all known Class Is and FSs in each cloud • Magnitude bias • Population distributed in all clouds • Not densely clustered (except in Serpens) • Serpens and Orion: higher luminosities Multiplicity in Star Formation - Toronto - 16-18 May 2007

  12. New tight systems IRAS 04361+2547 ? VLT-NACO Ks HST-NICMOS H Terebey et al. (1998) 0.31’’ Duchene et al. (2007) Multiplicity in Star Formation - Toronto - 16-18 May 2007

  13. Results : multiplicity rates • 110-1400 AU: 27 +/- 6 % (Tau+Oph) • 14-1400 AU: 45 +/- 8 % (Tau+Oph) • 45-1400 AU: 30 +/- 6 % (all clouds) • consistent with Reipurth et al. (2004) • Factor ~1.5 excess over field stars • No cloud-to-cloud difference • First evidence for high early MF in Orion ! Multiplicity in Star Formation - Toronto - 16-18 May 2007

  14. Results : multiplicity rates • Dependence on evolutionary stage? NO! • Class I vs. FS sources: • No significant difference • Objects with extended envelope: • Supposedly younger than other ClassI objects • Seeing-limited observations suggested a trend… • … but diffraction-limited observations proved otherwise Multiplicity in Star Formation - Toronto - 16-18 May 2007

  15. Results : other properties • Masses unknown from luminosity and IR fluxes • Need HR spectroscopy for mass ratios • High-order multiples: 5 triples overall • Not more than found among T Tauri stars or, probably, field stars • No unstable multiple system • Already destroyed or never existed Multiplicity in Star Formation - Toronto - 16-18 May 2007

  16. Results: other properties • Same MF in all clouds but differences in the distribution of separations Orion is different from other clouds at the 2.7  level (99.3%) Taurus All Orion companions Needs confirmation with larger samples Ophiuchus Duchene et al. (2007) Multiplicity in Star Formation - Toronto - 16-18 May 2007

  17. Overview and implications • High multiplicity rate of Class I and FS sources in all clouds • Even in the Orion molecular cloud ! • No many-star systems left by ~105 yrs • Consistent with quasi-universal scenario • Small-scale physics dominates fragmentation and/or early dynamical evolution Multiplicity in Star Formation - Toronto - 16-18 May 2007

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