CIRIACO GODDIEuropean Southern Observatory

Disk-mediated accretion in a high-mass YSO and dynamical history in Orion BN/KL

Main collaborators Lincoln GreenhillHarvard-Smithsonian Center for Astrophysics

Lynn Matthews MIT Haystack Observatory

Liz Humphreys European Southern Observatory

Claire ChandlerNational Radio Astronomy Observatory

What might help?

Direct imaging at R < 102 AU

- Gas structure & dynamics, magnetic fields, etc.

- Radio/mm interferometers generally unable to probe inside 10-1000 AU

Multi-epoch observations of radio continuum sources - 3-D velocities of high-mass YSOs: hints on cluster dynamical evolution - Long temporal baselines required for measurable position displacements

Which are the physical properties of Disk/Outflow interfaces?- Sizes/Structures of Disks

- Acceleration and Collimation of Outflows

- Balance of forces vs radius (gravity/radiation/magnetic field)

Do dynamical interactions among high-mass YSOs play an

important role within dense protoclusters?

Focus on two questions to address in HMSF

Trapezium

BN/KL

The closest massive SFR: Orion BN/KLD = 4186 pc(Kim et al. 2008)

L ~ 105 L

O(200) km s-1 outflow (H2)(Kaifu et al. 2000)

What is powering Orion BN/KL?

A High Density Protocluster in BN/KL

– 20 IR peaks distributed over 20”– BN and IRc2 brightest IR sources,

but not enough to power the nebula!

1”

Source I

12.5um, Keck (θ≈0.5”)

BN

IRc2

Gre

enhi

ll et

al.

2004

H2 P[FeII]HST/Nic

Schu

ltz

et a

l. 19

99

Source I is a luminous, massive, embedded YSO

7mm - VLA

Reid et al. 2007; Goddi et al. submitted

Obscured up to 22 μm (AV ≥300) Ionized disk with R~40 AU

(λ7mm)

Source I

BN/KL BN and IRc sources

Transition Instrument Observations Resolution28SiO (v=1,2 J=1-0) VLBA 35 epochs over 2001-03 0.1 AU

28SiO (v=0 J=1-0) VLA 5 epochs in 10 yrs 25-100 AU7 mm continuum VLA 3 epochs in 8 yrs 25 AU

Dataset

λ7mm cont (VLA)

T=104 K

SiO v=0 J=1-0 (VLA)T~1000 K, n < 107 cm-3

150 AU

Goddi et al.Greenhill et al.Matthews et al.

The case of the high-mass YSO “Source I” in Orion BN/KLCollection of λ7mm observations of Source I at R<1000 AU

SiO v=1,2 J=1-0 (VLBA)T~2000 K, n=1010±1 cm-3

Radio Source I drives a “Low-Velocity” NE-SW outflow7mm SiO v=0+H2O 1.3cm (VLA )

Greenhill, Goddi, et al., in prep.

Proper motions of SiO maser spots over 4 epochs

500 AU

100 AU<R<1000 AU

18 km/s

RA (arcsec)

<Voutflow

> 18 km s-1

Rinn 100 AU

Rout 1000 AU

Mass-loss

~10-6 M⊙

yr-1

Tdyn 500 yr

Dec

(ar

csec

)

Matthews, Greenhill, Goddi, et al. 2010 ApJ,708, 80

Long-term VLBA imaging study of Source I

Western Bridge

Eastern Bridge

Dark B

and

North Arm

East Arm

South Arm

West Arm

Isolated Features

Stream

ers

Integrated Intensity over timeSiO v=1,2

1010±1 cm-3 1000-3000 KO(1000) Jy km s-1 peakT=21 months, ΔT~1 month

R<100 AU

Time-series of VLBA moment 0 images of SiO v=1,2 masers over 2 years

Matthews, Greenhill, Goddi, et al. submitted

R<100 AU

Integrated Intensity epoch-by-epochT=21 months, ΔT~1 monthR<100 AU

Physical flow of O(1000) independent clumps

•Radial flow (four arms) •Transverse

flow(bridge)

Interpretation:- bipolar outflow (limbs)- disk rotation

Matthews, Greenhill, Goddi, et al. 2010 ApJ,708, 80

3-D velocity field of SiO (v=1,2) maser emission

Matthews, Greenhill, Goddi, et al. submitted

3-D Velocities:

v = 5-25 km/sVave = 14 km/s

O(1000) Proper Motions 3-11 mo. lifetimes 3 & 4 month tracks 43395 spots (0.22 km s-1) Vpmo=0.8–24 km s-1

V3D=5.3–25.3 km s-1 <V3D>=14 km s-1

VLOS rotation- NE / SW axis- red/blue arms- declining rotation curve- ∇VLOS in bridge

Role of magnetic fields from curvature of p.mo trajectories

R =10-100 AU

Rotating disk with R~50 AU => v=1,2 SiO masers in bridge + 7mm cont Wide-angle, rotating wind from the disk=> v=1,2 SiO masers in four arms

R=100-1000 AU

Collimated outflow at v~20 km s-1

=> v=0 SiO maser proper motions

Model of Source I

Resolved the launch/collimation region of outflowIdentified a good example of disk-mediated accretion

Toy-model

Close Passage between Source I and BN

Smin(BN-I)=0.11”±0.18”, Tmin(BN-I)=550±10 yr

500 years ago BN and I were as close as 50-100 AU!Goddi et al. submittedSee also Gomez et al. 2008

2”

Dynamical Interaction in BN/KL

VI≈15 km/s

VBN≈26 km/s

ONC-absolute p.mo.P.mo of BN relative to I

7mm, VLA (θ≈0.05”),3 epochs in 7 years

I

12.5um, Keck (θ≈0.5”)BN

Gre

en

hill

et a

l. 2

004

Triple-system decay in BN/KL

• Formation of a binary among the most massive bodies

• Binary and third object both are ejected with high speed

- VBN~2VI ➟ Source I is the binary and BN the escaper

Adapted from Reipurth 2000

Linear momentum conservation

MIVI=MBNVBN => VBN=2VI => MI=2MBN and MBN=10M

Mass of Source I MI=20M

Mechanical energy conservation

½(MIVI2+MBNVBN

2) = GM1IM2I/2a

Binary orbital separation a<10 AU

Which are mass and orbit of the binary?

Goddi et al. submitted; see also Gomez et al. 2008

Source I is a massive (20M) and tight (<10 AU) binary

I

I

BN

BN

N-body simulationInitial systems (binary+single):1) Mbin=10+10M, Abin=10 AU2) Msing=10M, S(bin-sing)=500AU

Results from 1000 cases:Ejections in 16% of casesImpact Periastron ~tens of AU Vbin=15 km/s, Vsing=30 km/sAbin=4 AU, Egrav~5 1047 erg

After 50yrs from the encounter

After 500yrs from the encounter

Goddi et al. submitted

Egrav bin=5x1047erg Ekin BN+I=2x1047ergEH2-flow=4x1047erg

The “hardening” of the binary would provide enough energy to account for the kinetic energy of both runaway stars and the fast H2 outflow!

; see also Zapata et al. 2009

Can the original disk(s) survive the collision?The encounter between a pre-existing binary (Source I) and a single (BN) enhances chances to retain the circumbinary disk

I. Source I is the best example of “resolved” accretion/outflow structure in HMSF

Laboratory to test processes (e.g., balance of B, L, G) at high-masses and constrain theories (e.g., disk-wind models)

II. Evidence of a complex dynamical history in Orion BN/KL

Is BN/KL “non-standard” or is this common in young clusters ? Studies with new EVLA and ALMA needed in other HMSFRs!

CONCLUSIONS

Candidate physical mechanisms driving the disk-wind

• Disk Photoionization (Hollenbach et al.1994) For M*~8 M, an ionized wind is set beyond the radius of the masers: cs < vesc . Unlikely.

• Dust-mediated radiation pressure (Elitzur 1982): Dust and gas are mixed at R<100 AU: Lmod=105 L, Ṁmod=10-3 M yr-1

Gas-φ SiO. Too little dust. Unlikely.

• Line-Driven winds (Drew et al. 1998): vw≥400 km/s, ρw<<10-14 g cm-3 inconsistent with vmas<30 km/s, ρmas>10-14 g cm-3

• MHD disk-winds (Konigl & Pudritz 2000): Maser features are detected along curved and helical filaments, indicating that magnetic fields may play a role in launching and shaping the wind

Most likely.

Morphological evolution of individual maser features over 2 yrs

Do SiO masers trace physical gas motion?Supportive evidence: Two independent kinematic components Slow evolution of clump morphology

Inconsistent with shock propagation in inhomogeneous medium Small scatter of centroids about linear proper motions Consistency of Vlos

Similar appearance over a range of physical conditions