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European Southern Observatory

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Presentation on theme: "European Southern Observatory"— Presentation transcript:

1 European Southern Observatory
Disk-mediated accretion in a high-mass YSO and dynamical history in Orion BN/KL CIRIACO GODDI European Southern Observatory Main collaborators Lincoln Greenhill Harvard-Smithsonian Center for Astrophysics Lynn Matthews MIT Haystack Observatory Liz Humphreys European Southern Observatory Claire Chandler National Radio Astronomy Observatory

2 Focus on two questions to address in HMSF
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? What might help? Direct imaging at R < 102 AU - Gas structure & dynamics, magnetic fields, etc. - Radio/mm interferometers generally unable to probe inside 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

3 The closest massive SFR: Orion BN/KL
D = 4186 pc (Kim et al. 2008) L ~ 105 L O(200) km s-1 outflow (H2) (Kaifu et al. 2000) BN/KL Trapezium What is powering Orion BN/KL?

4 A High Density Protocluster in BN/KL
H2 P[FeII] HST/Nic Schultz et al. 1999 BN/KL BN and IRc sources 20 IR peaks distributed over 20” BN and IRc2 brightest IR sources, but not enough to power the nebula! Source I 12.5um, Keck (θ≈0.5”) BN IRc2 Greenhill et al. 2004 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 1” Zooming into the center of the nebula, we identify a cluster of IR sources, The most prominent IR sources are BN and Irc2, which however are not bright enough to explain the high luminosity of BNKL Source I is a luminous, massive, embedded YSO

5 The case of the high-mass YSO “Source I” in Orion BN/KL
Collection of λ7mm observations of Source I at R<1000 AU SiO v=0 J=1-0 (VLA) T~1000 K, n < 107 cm-3 λ7mm cont (VLA) T=104 K SiO v=1,2 J=1-0 (VLBA) T~2000 K, n=1010±1 cm-3 Goddi et al. Greenhill et al. Matthews et al. 150 AU Transition Instrument Observations Resolution 28SiO (v=1,2 J=1-0) VLBA epochs over AU 28SiO (v=0 J=1-0) VLA epochs in 10 yrs AU 7 mm continuum VLA epochs in 8 yrs AU Dataset

6 Radio Source I drives a “Low-Velocity” NE-SW outflow
7mm SiO v=0+H2O 1.3cm (VLA ) 18 km/s Dec (arcsec) 500 AU Proper motions of SiO maser spots over 4 epochs open Q: what confines flow? open Q: what enables 102x spread in density implied by species overlap? <Voutflow> 18 km s-1 Rinn 100 AU Rout 1000 AU Mass-loss ~10-6 M⊙ yr-1 Tdyn 500 yr RA (arcsec) 100 AU<R<1000 AU Greenhill, Goddi, et al., in prep.

7 Long-term VLBA imaging study of Source I
Integrated Intensity over time SiO v=1,2 1010±1 cm K O(1000) Jy km s-1 peak T=21 months, ΔT~1 month R<100 AU Isolated Features North Arm East Arm South Arm West Arm Western Bridge Eastern Bridge Dark Band Streamers Matthews, Greenhill, Goddi, et al ApJ,708, 80

8 Time-series of VLBA moment 0 images of SiO v=1,2 masers over 2 years
Integrated Intensity epoch-by-epoch T=21 months, ΔT~1 month R<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 ApJ,708, 80 R<100 AU Matthews, Greenhill, Goddi, et al. submitted

9 3-D velocity field of SiO (v=1,2) maser emission
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 3-D Velocities: v = 5-25 km/s Vave = 14 km/s Role of magnetic fields from curvature of trajectories VLOS rotation NE / SW axis red/blue arms declining rotation curve ∇VLOS in bridge Two loci. Limb and front edge of flow. Bipolar funnel flow. Outflow. Rotation and expansion in the bridge Backside emission Matthews, Greenhill, Goddi, et al. submitted

10 Model of Source I R =10-100 AU R=100-1000 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= AU Collimated outflow at v~20 km s-1 => v=0 SiO maser proper motions Toy-model Resolved the launch/collimation region of outflow Identified a good example of disk-mediated accretion

11 500 years ago BN and I were as close as 50-100 AU!
Dynamical Interaction in BN/KL Close Passage between Source I and BN 7mm, VLA (θ≈0.05”),3 epochs in 7 years 12.5um, Keck (θ≈0.5”) VI≈15 km/s VBN≈26 km/s ONC-absolute of BN relative to I BN Greenhill et al. 2004 I IF I DONT INCLUDE THE NEXT SLIDE, I NEED TO INCLUDE HERE: Source I is the binary (M=20MS,A=10AU) and BN the escaper 2” Smin(BN-I)=0.11”±0.18”, Tmin(BN-I)=550±10 yr 500 years ago BN and I were as close as AU! Goddi et al. submitted See also Gomez et al. 2008

12 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 Linear momentum conservation MIVI=MBNVBN => VBN=2VI => MI=2MBN and MBN=10M Mass of Source I MI=20M Mechanical energy conservation ½(MIVI2+MBNVBN2) = 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 The positive kinetic energy is compensated by the negative binding energy associated with the binary Source I is a massive (20M) and tight (<10 AU) binary Adapted from Reipurth 2000

13 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 BN N-body simulation Initial systems (binary+single): 1) Mbin=10+10M, Abin=10 AU 2) Msing=10M, S(bin-sing)=500AU Results from 1000 cases: Ejections in 16% of cases Impact Periastron ~tens of AU Vbin=15 km/s, Vsing=30 km/s Abin=4 AU, Egrav~ erg After 50yrs from the encounter After 500yrs from the encounter Goddi et al. submitted Egrav bin=5x1047erg Ekin BN+I=2x1047erg EH2-flow=4x1047erg -The main problem is to avoid the intruder and the more massive companion to stick together in a new binary and eject the low-mass companion M binary required to avoid swapping of low-mass companion -The “hardening” of the binary would provide enough energy to account for the kinetic energy of both runaway stars and the fast H2 outflow Work in progress Ongoing N-body simulations to assess effects of stellar encounters on disks Mdyn cluster ~20M >Mdyn sio ~8M -dynamical effect of non-gravitational forces? 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

14 CONCLUSIONS 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) 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! 2 LESSONS LEARNED 1) Whatever is the actual history of Source I in BN/KL, our detailed study will drive people to figure out the balance of physics in a massive YSO when B, L, G are all at work 2) Is BN/KL “non-standard” or dynamical events common in massive, dense protoclusters?

15 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.

16 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 Morphological evolution of individual maser features over 2 yrs

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