gaspard duchêne university of california berkeley observatoire de grenoble g. duchêne -...
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G. Duchêne - Circumstellar disks and young stars - IAUS 270 - Barcelona, June 1st 2010
CIRCUMSTELLAR DISKS AND YOUNG
STARSGaspard DuchêneUniversity of California Berkeley
Observatoire de Grenoble
G. Duchêne - Circumstellar disks and young stars - IAUS 270 - Barcelona, June 1st 2010
On the importance of disks An inescapable outcome of star formation
The main angular momentum depository Birthsite of planetary systems
And driver of subsequent evolution Tracer of a star’s dynamical evolution
Influence of companions, environment
G. Duchêne - Circumstellar disks and young stars - IAUS 270 - Barcelona, June 1st 2010
On the importance of disks An inescapable outcome of star formation
The main angular momentum depository Birthsite of planetary systems
And driver of subsequent evolution Tracer of a star’s dynamical evolution
Influence of companions, environment
A critical ‘boundary condition’ for starformation theories and simulations
Disks in the T Tauri phase Over the first few Myr, disk proportion
declines around T Tauri starsRelates/informs planet formation and disk
dissipation
G. Duchêne - Circumstellar disks and young stars - IAUS 270 - Barcelona, June 1st 2010
Disks in the T Tauri phase Over the first few Myr, disk proportion
declines around T Tauri starsRelates/informs planet formation and disk
dissipation ≥90% at the very beginning
Hernández et al. (2007)
Very few stars are born withno circumstellar disk
G. Duchêne - Circumstellar disks and young stars - IAUS 270 - Barcelona, June 1st 2010
Disks as a function of M★
Proportion of disks varies very little with central stellar mass (from 0.05 to ~5 M)
Orion
Taurus
Cha I IC 348
mass
mass
Hillenbrand et al. (1998)
Luhman et al. (2010)
G. Duchêne - Circumstellar disks and young stars - IAUS 270 - Barcelona, June 1st 2010
Disks and environment
Presence of nearby high-mass stars has little influence on initial disk proportion
Hillenbrand et al. (1998)Hernández etal. (2007)
θ1C Ori
100%
G. Duchêne - Circumstellar disks and young stars - IAUS 270 - Barcelona, June 1st 2010
Disks orientation
The angular momentum of disks is randomly oriented w.r.t. local B fieldIn Taurus
Is it representative… of all SFRs?… of earlier phases?
|PAsystem – PAB field|
random
Ménard & Duchêne (2004)
G. Duchêne - Circumstellar disks and young stars - IAUS 270 - Barcelona, June 1st 2010
Disks in binary/multiple systems
Relative orientation between angular momentum vectors may be primordialGeneral but imperfect alignment
Simon etal. (2000)
Monin etal. (2007)
J pri
mar
y vs
Jse
con
dar
y
Circumbinary diskparallel to inner orbit
G. Duchêne - Circumstellar disks and young stars - IAUS 270 - Barcelona, June 1st 2010
Total disk mass and size
Disks are generally gravitationally stableMajor selection bias!
mass
Natta et al. (2000)
Natta et al. (2000)
G. Duchêne - Circumstellar disks and young stars - IAUS 270 - Barcelona, June 1st 2010
Total disk mass and size
Disks are generally gravitationally stableMajor selection bias!
Disk sizes show no trend… with age… with stellar mass
However…
mass
Natta et al. (2000)
Natta et al. (2000)
G. Duchêne - Circumstellar disks and young stars - IAUS 270 - Barcelona, June 1st 2010
Total disk mass and size
Disks are generally gravitationally stableMajor selection bias!
Disk sizes show no trend… with age… with stellar mass
However…
mass
Natta et al. (2000)
These disks are not representative of
star formation (too old)!Natta et al. (2000)
G. Duchêne - Circumstellar disks and young stars - IAUS 270 - Barcelona, June 1st 2010
Disks and embedded protostars
Disks are assumed to be prevalent in earlier phases of stellar evolutionIssue: contamination by massive envelope
G. Duchêne - Circumstellar disks and young stars - IAUS 270 - Barcelona, June 1st 2010
Disks and embedded protostars
Disks are assumed to be prevalent in earlier phases of stellar evolutionIssue: contamination by massive envelope
Disks around protostars may be quite massive and large (150-300 AU)Handful of sourcesSelection bias?
Topic under debate! Class 0
Class I
Jörgensen et al. (2005, 2009);see also Enoch et al. (2009), Maury et al. (2009)
G. Duchêne - Circumstellar disks and young stars - IAUS 270 - Barcelona, June 1st 2010
Summary
Disks are prevalent around young stars, from brown dwarfs to intermediate-mass stars
Disks around embedded protostars are the best probes/tests of star formation theory
Among young stars, the disk presence and orientation are the easiest to assessDisk mass, radius, …, are model-dependent and
generally biasedDifficult to compare observations and models