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CIRIACO GODDI European Southern Observatory Disk-mediated accretion in a high-mass YSO and dynamical history in Orion BN/KL Main collaborators Lincoln.

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Presentation on theme: "CIRIACO GODDI European Southern Observatory Disk-mediated accretion in a high-mass YSO and dynamical history in Orion BN/KL Main collaborators Lincoln."— Presentation transcript:

1 CIRIACO GODDI European Southern Observatory Disk-mediated accretion in a high-mass YSO and dynamical history in Orion BN/KL 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 What might help?  Direct imaging at R < 10 2 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  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

3 Trapezium BN/KL The closest massive SFR: Orion BN/KL D = 418  6 pc (Kim et al. 2008) L ~ 10 5 L  O(200) km s -1 outflow (H 2 ) (Kaifu et al. 2000) What is powering Orion BN/KL?

4 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 Greenhill et al H 2 P  [FeII] HST/Nic Schultz et al Source I is a luminous, massive, embedded YSO 7mm - VLA Reid et al. 2007; Goddi et al. submitted Obscured up to 22 μm (A V ≥300) Ionized disk with R~40 AU (λ7mm) Source I BN/K L BN and IRc sources

5 Transition Instrument Observations Resolution 28 SiO (v=1,2 J=1-0) VLBA 35 epochs over AU 28 SiO (v=0 J=1-0) VLA 5 epochs in 10 yrs AU 7 mm continuum VLA 3 epochs in 8 yrs 25 AU Dataset λ7mm cont (VLA) T=10 4 K SiO v=0 J=1-0 (VLA) T~1000 K, n < 10 7 cm AU Goddi et al. Greenhill et al. Matthews et al. 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=1,2 J=1-0 (VLBA) T~2000 K, n=10 10±1 cm -3

6 Radio Source I drives a “Low-Velocity” NE-SW outflow 7mm SiO v=0+H 2 O 1.3cm (VLA ) Greenhill, Goddi, et al., in prep. Proper motions of SiO maser spots over 4 epochs 500 AU 100 AU

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

8 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-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

9 3-D velocity field of SiO (v=1,2) maser emission Matthews, Greenhill, Goddi, et al. submitted 3-D Velocities:  v = 5-25 km/s V ave = 14 km/s O(1000) Proper Motions  3-11 mo. lifetimes  3 & 4 month tracks  spots (0.22 km s -1 )  V pmo =0.8–24 km s -1  V 3D =5.3–25.3 km s -1  =14 km s -1 V LOS rotation - NE / SW axis - red/blue arms - declining rotation curve - ∇ V LOS in bridge Role of magnetic fields from curvature of trajectories

10 R = 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 Model of Source I  Resolved the launch/collimation region of outflow  Identified a good example of disk-mediated accretion Toy-model

11 Close Passage between Source I and BN S min (BN-I)=0.11”±0.18”, T min (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 ” Dynamical Interaction in BN/KL V I ≈15 km/s V BN ≈26 km/s ONC-absolute of BN relative to I 7mm, VLA (θ≈0.05”),3 epochs in 7 years I 12.5um, Keck (θ≈0.5”) BN Greenhill et al. 2004

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 - V BN ~2V I ➟ Source I is the binary and BN the escaper Adapted from Reipurth 2000 Linear momentum conservation M I V I =M BN V BN => V BN =2V I => M I =2M BN and M BN =10M   Mass of Source I M I =20M  Mechanical energy conservation ½(M I V I 2 +M BN V BN 2 ) = GM 1I M 2I /2a  Binary orbital separation a<10 AU Which are mass and orbit of the binary? Goddi et al. submitted; see also Gomez et al Source I is a massive (20M  ) and tight (<10 AU) binary

13 I I BNBN BNBN N-body simulation Initial systems (binary+single): 1) M bin =10+10M , A bin =10 AU 2) M sing =10M , S(bin-sing)=500AU Results from 1000 cases: Ejections in 16% of cases Impact Periastron ~tens of AU V bin =15 km/s, V sing =30 km/s A bin =4 AU, E grav ~ erg After 50yrs from the encounter After 500yrs from the encounter Goddi et al. submitted E grav bin =5x10 47 erg E kin BN+I =2x10 47 erg E H2-flow =4x10 47 erg Work in progress Ongoing N-body simulations to assess effects of stellar encounters on disks M dyn cluster ~20M  >M dyn 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 H 2 outflow! ; see also Zapata et al 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

14 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) I. 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

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: c s < v esc. Unlikely. Dust-mediated radiation pressure (Elitzur 1982): Dust and gas are mixed at R<100 AU: L mod =10 5 L , Ṁ mod =10 -3 M  yr -1 Gas-φ SiO. Too little dust. Unlikely. Line-Driven winds (Drew et al. 1998): v w ≥400 km/s, ρ w 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 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

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