Gas Clouds in the Galactic Center

Transcript

1. Magnetized Gas Clouds in the Galactic Center Mike McCourt, Ryan O’Leary, Ann-Marie Madigan, & Eliot Quataert
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4. Outline “Gas Clouds in the Galactic Center” Dynamics of Magnetized Clouds Disruption (McCourt, O’Leary, Madigan, & Quataert) Acceleration Making Gas Clouds Work for Us G’s twisted sister (McCourt & Madigan) Using G to probe the accretion flow
5. Dynamics of Magnetized Gas Clouds in Dilute Plasmas
6. Disruption Acceleration Rotation Conclusion Background Li et al. 2013 “Cloud Crushing:” tcrush ∼ ρcloud ρwind 1/2 Rcloud vwind
7. hydro t = 5 tcrush t = tstop Σcloud /(ρcloud Rcloud) 1 0.1 0.01 0.001 0.0
8. hydro t = 5 tcrush t = tstop z x z x y x y x Σcloud /(ρcloud Rcloud) 1 0.1 0.01 0.001 0.0
9. hydro t = 5 tcrush t = tstop z x z x z x z x y x y x y x y x Σcloud /(ρcloud Rcloud) 1 0.1 0.01 0.001 0.0
10. Disruption Acceleration Rotation Conclusion aside: initial conditions matter
11. Disruption Acceleration Rotation Conclusion Magnetically-Enhanced Drag Force ✽ ✽ ✽ t / tcrush distance / Rcloud 0 5 10 15 10 20 30 40 50 60 70 80 Hydro βwind = 10 βwind = 1 βwind = 0.1
12. Putting Gas Clouds to Work: Probing the Galactic Center Accretion Flow
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14. Disruption Acceleration Rotation Conclusion (Re-)Discovery of G G G a . ± . . ± . e . ± . . ± . (Pfuhl et al. 2015)
15. Disruption Acceleration Rotation Conclusion (Re-)Discovery of G G G a . ± . . ± . e . ± . . ± . (Pfuhl et al. 2015)
16. Disruption Acceleration Rotation Conclusion (Re-)Discovery of G G G a . ± . . ± . e . ± . . ± . J . . (Pfuhl et al. 2015)
17. Disruption Acceleration Rotation Conclusion (Re-)Discovery of G G G a . ± . . ± . e . ± . . ± . J . . i . ± . . ± . Ω . ± . . ± . ω . ± . . ± . (Pfuhl et al. 2015)
18. Disruption Acceleration Rotation Conclusion (Re-)Discovery of G G G a . ± . . ± . e . ± . . ± . J . . i . ± . . ± . Ω . ± . . ± . ω . ± . . ± . (Pfuhl et al. 2015)
19. “Sometimes a man wants to be stupid if it lets him do a thing his cleverness forbids. ” — John Steinbeck
20. v cloud v wind F drag
21. Disruption Acceleration Rotation Conclusion A Simple Model d2r dt2 = − GM• r r3 − ρbg (r) Mcloud × 1 + 2 βM2 × C−1 · diag R2 cloud , Rcloud Lcloud , Rcloud Lcloud · (C · vrel )2 ρbg (r) = ρ0 r r0 −a Tbg (r) = GM• r vbg (r) = fkep GM• r 1/2 J × r J r
22. Disruption Acceleration Rotation Conclusion Comparison with the Data V v los (pc/yr) −0.0015 0.0000 0.0015 time (JD) ∆v 1990 2000 2010 2020 2030 2040 2050 –0.001 0.000 0.001 RA (pc) dec. (pc) −0.005 0.000 0.005 0.010 0.015 –0.0075 –0.0050 –0.0025 0.0000 0.0025
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24. Disruption Acceleration Rotation Conclusion Constraining Accretion Flow Parameters θ φ 30◦ 60◦ 120◦ 150◦ –90◦ 90◦ 0 π/4 π/2 3π/4 π –π –π/2 0 π/2 π α β 0.0 0.3 0.6 0.9 10−1 1 10 102 f kep (L cloud − R cloud)/R cloud 0.0 0.2 0.4 0.6 0.8 1.0 10 102
25. Disruption Acceleration Rotation Conclusion Constraining Accretion Flow Parameters α β 0.0 0.3 0.6 0.9 10−1 1 10 102 f kep (L cloud − R cloud)/R cloud 0.0 0.2 0.4 0.6 0.8 1.0 10 102 θ φ 30◦ 60◦ 120◦ 150◦ –135◦ –90◦ –45◦ 45◦ 90◦ 135◦ 0 π/4 π/2 3π/4 π –π –π/2 0 π/2 π
26. Disruption Acceleration Rotation Conclusion Constraining Accretion Flow Parameters α β 0.0 0.3 0.6 0.9 10−1 1 10 102 f kep (L cloud − R cloud)/R cloud 0.0 0.2 0.4 0.6 0.8 1.0 10 102 θ φ 30◦ 60◦ 120◦ 150◦ –135◦ –90◦ –45◦ 45◦ 90◦ 135◦ 0 π/4 π/2 3π/4 π –π –π/2 0 π/2 π
27. Disruption Acceleration Rotation Conclusion Constraining Accretion Flow Parameters α β 0.0 0.3 0.6 0.9 10−1 1 10 102 f kep (L cloud − R cloud)/R cloud 0.0 0.2 0.4 0.6 0.8 1.0 10 102 θ φ 30◦ 60◦ 120◦ 150◦ –135◦ –90◦ –45◦ 45◦ 90◦ 135◦ 0 π/4 π/2 3π/4 π –π –π/2 0 π/2 π
28. Disruption Acceleration Rotation Conclusion Constraining Accretion Flow Parameters α β 0.0 0.3 0.6 0.9 10−1 1 10 102 f kep (L cloud − R cloud)/R cloud 0.0 0.2 0.4 0.6 0.8 1.0 10 102 θ φ 30◦ 60◦ 120◦ 150◦ –135◦ –90◦ –45◦ 45◦ 90◦ 135◦ 0 π/4 π/2 3π/4 π –π –π/2 0 π/2 π
29. Disruption Acceleration Rotation Conclusion Constraining Accretion Flow Parameters α β 0.0 0.3 0.6 0.9 10−1 1 10 102 f kep (L cloud − R cloud)/R cloud 0.0 0.2 0.4 0.6 0.8 1.0 10 102 θ φ 30◦ 60◦ 120◦ 150◦ –135◦ –90◦ –45◦ 45◦ 90◦ 135◦ 0 π/4 π/2 3π/4 π –π –π/2 0 π/2 π
30. Disruption Acceleration Rotation Conclusion Constraining Accretion Flow Parameters α β 0.0 0.3 0.6 0.9 10−1 1 10 102 f kep (L cloud − R cloud)/R cloud 0.0 0.2 0.4 0.6 0.8 1.0 10 102 θ φ 30◦ 60◦ 120◦ 150◦ –135◦ –90◦ –45◦ 45◦ 90◦ 135◦ 0 π/4 π/2 3π/4 π –π –π/2 0 π/2 π
31. Disruption Acceleration Rotation Conclusion Summary Magnetized Clouds Tangled magnetic fields internal to the clouds can inhibit disruption by shear instabilities. Magnetic fields external to the cloud can enhance the drag force, strongly coupling clouds to their environment. Depends on the internal structure of clouds; need to know how they formed to predict future evolution. Accretion Flow Given enough assumptions, G and G can be used to constrain properties of the accretion flow in the galactic center. If it works, only constraint at intermediate radii. Find an orientation for the rotation axis consistent with EHT determinations at smaller scales. Please keep following G!