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Multiplicity among embedded protostars
Multiplicity among embedded protostars
Gaspard Duchêne (Grenoble)J. Bouvier, S. Bontemps, P. André, F.
Motte, A. Djupvik, A. Ghez
Gaspard Duchêne (Grenoble)J. Bouvier, S. Bontemps, P. André, F.
Motte, A. Djupvik, A. Ghez
Multiplicity in Star Formation - Toronto - 16-18 May 2007
Multiplicity in Star Formation - Toronto - 16-18 May 2007
General backgroundGeneral background
Multiplicity well studied for ages 106 yrs
Multiplicity well studied for ages 106 yrs
Large excess in someyoung populations
Apparent dependenceon environment
Scaled MF fromVB surveys
fieldopenclusters
T Tauristars
Multiplicity in Star Formation - Toronto - 16-18 May 2007
General backgroundGeneral background
Interpretation still ambiguous:Interpretation still ambiguous:
Scaled MF fromVB surveys
?
Multiplicity in Star Formation - Toronto - 16-18 May 2007
General backgroundGeneral background
Interpretation still ambiguous:Interpretation still ambiguous:
Scaled MF fromVB surveys
Tracer of differentinitial states ?
Physics of corefragmentation
Higher cloud mass
Multiplicity in Star Formation - Toronto - 16-18 May 2007
General backgroundGeneral background
Interpretation still ambiguous:Interpretation still ambiguous:
Scaled MF fromVB surveys
Tracer of differentinitial states ?
Physics of corefragmentation
Stellar dynamics
Tracer of a differentearly evolution ?
Denser clusters
Multiplicity in Star Formation - Toronto - 16-18 May 2007
General backgroundGeneral background
Need to survey even younger systems:Embedded protostars !
Need to survey even younger systems:Embedded protostars ! Scaled MF from
VB surveys
?
Class 0age ~ 104 yrs, radio
Class Iage ~ 105 yrs, IR
Reipurth (2000)
80-85% MF
Multiplicity in Star Formation - Toronto - 16-18 May 2007
This work : basic presentation
This work : basic presentation
Objective: survey of protostars with deep, high resolution, NIR imaging
Several SFRsTaurus vs. Orion
Focus onClass IFlat Spectrum (FS)
Objective: survey of protostars with deep, high resolution, NIR imaging
Several SFRsTaurus vs. Orion
Focus onClass IFlat Spectrum (FS)Kaas et al. (2004)
FS
Class I
Multiplicity in Star Formation - Toronto - 16-18 May 2007
This work : basic presentation
This work : basic presentation
Observations:Seeing-limited: CFHT-IR (0.6”) JHKDiffraction-limited: VLT-NACO (0.07”)
HKL’
Observations:Seeing-limited: CFHT-IR (0.6”) JHKDiffraction-limited: VLT-NACO (0.07”)
HKL’
1’’ 10’’ 0.1’’ 1’’ 10’’
CFHT-IR VLT-NACO
~7 mag
~7 mag
Duchene et al. (2004) Duchene et al. (2007)
Multiplicity in Star Formation - Toronto - 16-18 May 2007
Additional sampleAdditional sample
When available, we also added older HST/NICMOS images to our surveySomewhat poorer
resolution (0.15’’)Higher PSF stabilityHigher sensitivity
(fainter targets)
When available, we also added older HST/NICMOS images to our surveySomewhat poorer
resolution (0.15’’)Higher PSF stabilityHigher sensitivity
(fainter targets)Padgett et al. (1999)0.24’’
Multiplicity in Star Formation - Toronto - 16-18 May 2007
This work : sampleThis work : sample
Overview of our sample:Overview of our sample:
CFHT-IR VLT-NACO
Class I FS Class I FS
Taurus 12 10 11 5
Ophiuchus 16 25 12 10
Serpens - - 2 6
Orion - - 4 8
Multiplicity in Star Formation - Toronto - 16-18 May 2007
This work : sampleThis work : sample
Sample represents ~40% of all known Class Is and FSs in each cloudMagnitude bias
Population distributed in all cloudsNot densely clustered (except in
Serpens)Serpens and Orion: higher
luminosities
Sample represents ~40% of all known Class Is and FSs in each cloudMagnitude bias
Population distributed in all cloudsNot densely clustered (except in
Serpens)Serpens and Orion: higher
luminosities
Multiplicity in Star Formation - Toronto - 16-18 May 2007
New tight systemsNew tight systemsIRAS 04361+2547
VLT-NACO Ks
HST-NICMOS H
Duchene et al. (2007)
Terebey et al. (1998)
0.31’’
?
Multiplicity in Star Formation - Toronto - 16-18 May 2007
Results : multiplicity ratesResults : 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 starsNo cloud-to-cloud difference
First evidence for high early MF in Orion !
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 starsNo cloud-to-cloud difference
First evidence for high early MF in Orion !
Multiplicity in Star Formation - Toronto - 16-18 May 2007
Results : multiplicity ratesResults : multiplicity rates
Dependence on evolutionary stage? NO!Class I vs. FS sources:
No significant difference
Objects with extended envelope:Supposedly younger than other ClassI objectsSeeing-limited observations suggested a
trend…… but diffraction-limited observations proved
otherwise
Dependence on evolutionary stage? NO!Class I vs. FS sources:
No significant difference
Objects with extended envelope:Supposedly younger than other ClassI objectsSeeing-limited observations suggested a
trend…… but diffraction-limited observations proved
otherwise
Multiplicity in Star Formation - Toronto - 16-18 May 2007
Results : other propertiesResults : other properties
Masses unknown from luminosity and IR fluxesNeed HR spectroscopy for mass ratios
High-order multiples: 5 triples overallNot more than found among T Tauri
stars or, probably, field starsNo unstable multiple system
Already destroyed or never existed
Masses unknown from luminosity and IR fluxesNeed HR spectroscopy for mass ratios
High-order multiples: 5 triples overallNot more than found among T Tauri
stars or, probably, field starsNo unstable multiple system
Already destroyed or never existed
Multiplicity in Star Formation - Toronto - 16-18 May 2007
Results: other propertiesResults: other properties
Same MF in all clouds but differences in the distribution of separations
Same MF in all clouds but differences in the distribution of separations
Duchene et al. (2007)
Taurus
OphiuchusNeeds confirmationwith larger samples
Orion is different fromother clouds at the2.7 level (99.3%)
All Orioncompanions
Multiplicity in Star Formation - Toronto - 16-18 May 2007
Overview and implicationsOverview and implications
High multiplicity rate of Class I and FS sources in all cloudsEven in the Orion molecular cloud !No many-star systems left by ~105 yrs
Consistent with quasi-universal scenarioSmall-scale physics dominates
fragmentation and/or early dynamical evolution
High multiplicity rate of Class I and FS sources in all cloudsEven in the Orion molecular cloud !No many-star systems left by ~105 yrs
Consistent with quasi-universal scenarioSmall-scale physics dominates
fragmentation and/or early dynamical evolution