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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


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


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


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


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)


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%


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)


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


Total disk mass and size Disks are generally gravitationally stable

Major selection bias!

mass

Natta et al. (2000)Natta et al. (2000)



Major selection bias! Disk sizes show no trend

… with age… with stellar mass

However…

mass

Natta et al. (2000)Natta et al. (2000)



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)


Disks and embedded protostars Disks are assumed to be prevalent in

earlier phases of stellar evolutionIssue: contamination by massive envelope


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)


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