Circumstellar Disks and young stars
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Transcript of Circumstellar Disks and young stars
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 prim
ary v
s J s
econ
dary
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 stable
Major 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 stable
Major 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 stable
Major 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