Presentation on theme: "European Southern Observatory"— Presentation transcript:
1European Southern Observatory Disk-mediated accretion in a high-mass YSO and dynamical history in Orion BN/KLCIRIACO GODDIEuropean Southern ObservatoryMain collaboratorsLincoln GreenhillHarvard-Smithsonian Center for AstrophysicsLynn MatthewsMIT Haystack ObservatoryLiz HumphreysEuropean Southern ObservatoryClaire ChandlerNational Radio Astronomy Observatory
2Focus on two questions to address in HMSF Which are the physical properties of Disk/Outflow interfaces?Sizes/Structures of DisksAcceleration and Collimation of OutflowsBalance 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 AUMulti-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
3The closest massive SFR: Orion BN/KL D = 4186 pc(Kim et al. 2008)L ~ 105 LO(200) km s-1outflow (H2)(Kaifu et al. 2000)BN/KLTrapeziumWhat is powering Orion BN/KL?
4A High Density Protocluster in BN/KL H2 P[FeII]HST/NicSchultz et al. 1999BN/KLBN and IRc sources20 IR peaks distributed over 20”BN and IRc2 brightest IR sources, but not enough to power the nebula!Source I12.5um, Keck (θ≈0.5”)BNIRc2Greenhill et al. 20047mm - VLAReid et al. 2007; Goddi et al. submittedObscured up to 22 μm (AV ≥300)Ionized disk with R~40 AU (λ7mm)Source I1”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 BNKLSource I is a luminous, massive, embedded YSO
5The case of the high-mass YSO “Source I” in Orion BN/KL Collection of λ7mm observations of Source I at R<1000 AUSiO v=0 J=1-0 (VLA)T~1000 K, n < 107 cm-3λ7mm cont (VLA)T=104 KSiO v=1,2 J=1-0 (VLBA)T~2000 K, n=1010±1 cm-3Goddi et al.Greenhill et al.Matthews et al.150 AUTransition Instrument Observations Resolution28SiO (v=1,2 J=1-0) VLBA epochs over AU28SiO (v=0 J=1-0) VLA epochs in 10 yrs AU7 mm continuum VLA epochs in 8 yrs AUDataset
6Radio Source I drives a “Low-Velocity” NE-SW outflow 7mm SiO v=0+H2O 1.3cm (VLA )18 km/sDec (arcsec)500 AUProper motions of SiO maser spots over 4 epochsopen Q: what confines flow?open Q: what enables 102x spread in density implied by species overlap?<Voutflow>18 km s-1Rinn100 AURout1000 AUMass-loss~10-6 M⊙ yr-1Tdyn500 yrRA (arcsec)100 AU<R<1000 AUGreenhill, Goddi, et al., in prep.
7Long-term VLBA imaging study of Source I Integrated Intensityover timeSiO v=1,21010±1 cm KO(1000) Jy km s-1 peakT=21 months, ΔT~1 monthR<100 AUIsolated FeaturesNorth ArmEast ArmSouth ArmWest ArmWestern BridgeEastern BridgeDark BandStreamersMatthews, Greenhill, Goddi, et al ApJ,708, 80
8Time-series of VLBA moment 0 images of SiO v=1,2 masers over 2 years Integrated Intensity epoch-by-epochT=21 months, ΔT~1 monthR<100 AUPhysical flow of O(1000) independent clumpsRadial flow (four arms)Transverse flow(bridge)Interpretation:bipolar outflow (limbs)disk rotationMatthews, Greenhill, Goddi, et al ApJ,708, 80R<100 AUMatthews, Greenhill, Goddi, et al. submitted
93-D velocity field of SiO (v=1,2) maser emission O(1000) Proper Motions3-11 mo. lifetimes3 & 4 month tracks43395 spots (0.22 km s-1)Vpmo=0.8–24 km s-1V3D=5.3–25.3 km s-1<V3D>=14 km s-13-D Velocities:v = 5-25 km/sVave = 14 km/sRole of magnetic fields from curvature of p.mo trajectoriesVLOS rotationNE / SW axisred/blue armsdeclining rotation curve∇VLOS in bridgeTwo loci.Limb and front edge of flow.Bipolar funnel flow.Outflow.Rotation and expansion in the bridgeBackside emissionMatthews, Greenhill, Goddi, et al. submitted
10Model 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 contWide-angle, rotating wind from the disk=> v=1,2 SiO masers in four armsR= AUCollimated outflow at v~20 km s-1=> v=0 SiO maser proper motionsToy-modelResolved the launch/collimation region of outflowIdentified a good example of disk-mediated accretion
11500 years ago BN and I were as close as 50-100 AU! Dynamical Interaction in BN/KLClose Passage between Source I and BN7mm, VLA (θ≈0.05”),3 epochs in 7 years12.5um, Keck (θ≈0.5”)VI≈15 km/sVBN≈26 km/sONC-absolute p.mo.P.mo of BN relative to IBNGreenhill et al. 2004IIF I DONT INCLUDE THE NEXT SLIDE, I NEED TO INCLUDE HERE:Source I is the binary (M=20MS,A=10AU) and BN the escaper2”Smin(BN-I)=0.11”±0.18”, Tmin(BN-I)=550±10 yr500 years ago BN and I were as close as AU!Goddi et al. submittedSee also Gomez et al. 2008
12Triple-system decay in BN/KL Formation of a binary among the most massive bodiesBinary and third object both are ejected with high speed- VBN~2VI ➟ Source I is the binary and BN the escaperLinear momentum conservationMIVI=MBNVBN => VBN=2VI => MI=2MBN and MBN=10MMass of Source I MI=20MMechanical energy conservation½(MIVI2+MBNVBN2) = GM1IM2I/2aBinary orbital separation a<10 AUWhich are mass and orbit of the binary?Goddi et al. submitted; see also Gomez et al. 2008The positive kinetic energy is compensated by the negative binding energy associated with the binarySource I is a massive (20M) and tight (<10 AU) binaryAdapted from Reipurth 2000
13Can 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 diskIBNN-body simulationInitial systems (binary+single):1) Mbin=10+10M, Abin=10 AU2) Msing=10M, S(bin-sing)=500AUResults from 1000 cases:Ejections in 16% of casesImpact Periastron ~tens of AUVbin=15 km/s, Vsing=30 km/sAbin=4 AU, Egrav~ ergAfter 50yrs from the encounterAfter 500yrs from the encounterGoddi et al. submittedEgrav bin=5x1047ergEkin BN+I=2x1047ergEH2-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 outflowWork in progressOngoing N-body simulations to assess effects of stellar encounters on disksMdyn 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
14CONCLUSIONSSource I is the best example of “resolved” accretion/outflow structure in HMSFLaboratory 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/KLIs BN/KL “non-standard” or is this common in young clusters ? Studies with new EVLA and ALMA needed in other HMSFRs!2 LESSONS LEARNED1) 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 work2) Is BN/KL “non-standard” or dynamical events common in massive, dense protoclusters?
15Candidate 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-1Gas-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-3MHD disk-winds (Konigl & Pudritz 2000):Maser features are detected along curved and helical filaments, indicating thatmagnetic fields may play a role in launching and shaping the windMost likely.
16Do SiO masers trace physical gas motion? Supportive evidence:Two independent kinematic componentsSlow evolution of clump morphologyInconsistent with shock propagation in inhomogeneous mediumSmall scatter of centroids about linear proper motionsConsistency of VlosSimilar appearance over a range of physical conditionsMorphological evolution of individual maser features over 2 yrs