Multiplicity among embedded protostars

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


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



Interpretation still ambiguous:Interpretation still ambiguous:


?





Tracer of differentinitial states ?

Physics of corefragmentation

Higher cloud mass





Tracer of differentinitial states ?

Physics of corefragmentation

Stellar dynamics

Tracer of a differentearly evolution ?

Denser clusters



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


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




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)


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’’


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


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


New tight systemsNew tight systemsIRAS 04361+2547

VLT-NACO Ks

HST-NICMOS H

Duchene et al. (2007)

Terebey et al. (1998)

0.31’’

?


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 !


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


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


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


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

Multiplicity among embedded protostars

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