Magnetized Gas Clouds in the Galactic Center Mike McCourt, Ryan - PowerPoint PPT Presentation

Magnetized Gas Clouds in the Galactic Center Mike McCourt, Ryan O’Leary, Ann-Marie Madigan, & Eliot Quataert

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, in prep. ) � Using G to probe the accretion flow

Dynamics of Magnetized Gas Clouds in Dilute Plasmas

Disruption Acceleration Rotation Conclusion Background “Cloud Crushing:” � 1 / 2 R cloud � ρ cloud t crush ∼ v wind ρ wind Li et al. 2013

hydro t = 5 t crush t = t stop Σ cloud / ( ρ cloud R cloud ) 1 0.1 0.01 0.001 0.0

hydro z t = 5 t crush x y x z t = t stop x y x Σ cloud / ( ρ cloud R cloud ) 1 0.1 0.01 0.001 0.0

mhd hydro z z t = 5 t crush x x y y x x z z t = t stop x x y y x x Σ cloud / ( ρ cloud R cloud ) 1 0.1 0.01 0.001 0.0

Disruption Acceleration Rotation Conclusion aside: initial conditions matter

Disruption Acceleration Rotation Conclusion Magnetically-Enhanced Drag Force 80 Hydro 70 β wind = 10 β wind = 1 60 β wind = 0.1 distance / R cloud 50 ✽ 40 ✽ 30 20 10 ✽ 0 5 10 15 t / t crush

Putting Gas Clouds to Work: Probing the Galactic Center Accretion Flow

Disruption Acceleration Rotation Conclusion (Re-)Discovery of G G G a . ± . . ± . e . ± . . ± . (Pfuhl et al. 2014)

Disruption Acceleration Rotation Conclusion (Re-)Discovery of G G G a . ± . . ± . e . ± . . ± . (Pfuhl et al. 2014)

Disruption Acceleration Rotation Conclusion (Re-)Discovery of G G G a . ± . . ± . e . ± . . ± . J . . (Pfuhl et al. 2014)

Disruption Acceleration Rotation Conclusion (Re-)Discovery of G G G a . ± . . ± . e . ± . . ± . J . . i . ± . . ± . Ω . ± . . ± . ω . ± . . ± . (Pfuhl et al. 2014)

Disruption Acceleration Rotation Conclusion (Re-)Discovery of G G G a . ± . . ± . e . ± . . ± . J . . i . ± . . ± . Ω . ± . . ± . ω . ± . . ± . (Pfuhl et al. 2014)

“Sometimes a man wants to be stupid if it lets him do a thing his cleverness forbids. ” — John Steinbeck

“Sometimes a man wants to be stupid if it lets him do a thing his cleverness forbids. ” — John Steinbeck � Assume G and G are gas clouds, � Assume they follow the same trajectory � Assume they survive at least one pericenter passage

F drag v cloud v wind

Disruption Acceleration Rotation Conclusion A (too-)Simple Model d 2 r dt 2 = − GM • � r r 3 r ) ρ bg ( � 2 � � 1 + − × M cloud β M 2 � � × C − 1 · diag v rel ) 2 R 2 cloud , R cloud L cloud , R cloud L cloud · ( C · � � r � − a r ) = ρ 0 ρ bg ( � r 0 r ) = GM • T bg ( � r � 1 / 2 � � GM • J × � r v bg ( � r ) = f kep � r J r

Disruption Acceleration Rotation Conclusion Comparison with the Data 0.0025 0.0000 0.0015 ✽ v los (pc / yr) –0.0025 0.0000 dec. (pc) − 0.0015 –0.0050 –0.0075 0.001 ∆ v 0.000 –0.001 0.015 0.010 0.005 0.000 − 0.005 1990 2000 2010 2020 2030 2040 2050 RA (pc) time (JD)

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Disruption Acceleration Rotation Conclusion Making this Useful 10 2 10 2 π ( L cloud − R cloud ) / R cloud π/ 2 90 ◦ 10 120 ◦ 150 ◦ 30 ◦ 60 ◦ 10 φ β 0 1 – π/ 2 –90 ◦ 10 − 1 – π π/ 4 π/ 2 3 π/ 4 π 0 0.0 0.3 0.6 0.9 0.0 0.2 0.4 0.6 0.8 1.0 θ α f kep

Disruption Acceleration Rotation Conclusion Making this Useful 10 2 π ( L cloud − R cloud ) / R cloud 135 ◦ 10 π/ 2 90 ◦ 45 ◦ 0.0 0.2 0.4 0.6 0.8 1.0 30 ◦ 60 ◦ 120 ◦ 150 ◦ f kep φ 0 10 2 –45 ◦ 10 – π/ 2 –90 ◦ β 1 –135 ◦ 10 − 1 – π 0 π/ 4 π/ 2 3 π/ 4 π 0.0 0.3 0.6 0.9 θ α

Disruption Acceleration Rotation Conclusion Making this Useful 10 2 π ( L cloud − R cloud ) / R cloud 135 ◦ 10 π/ 2 90 ◦ 45 ◦ 0.0 0.2 0.4 0.6 0.8 1.0 30 ◦ 60 ◦ 120 ◦ 150 ◦ f kep φ 0 10 2 –45 ◦ 10 – π/ 2 –90 ◦ β 1 –135 ◦ 10 − 1 – π 0 π/ 4 π/ 2 3 π/ 4 π 0.0 0.3 0.6 0.9 θ α

Disruption Acceleration Rotation Conclusion Making this Useful 10 2 π ( L cloud − R cloud ) / R cloud 135 ◦ 10 π/ 2 90 ◦ 45 ◦ 0.0 0.2 0.4 0.6 0.8 1.0 30 ◦ 60 ◦ 120 ◦ 150 ◦ f kep φ 0 10 2 –45 ◦ 10 – π/ 2 –90 ◦ β 1 –135 ◦ 10 − 1 – π 0 π/ 4 π/ 2 3 π/ 4 π 0.0 0.3 0.6 0.9 θ α

Disruption Acceleration Rotation Conclusion Making this Useful 10 2 π ( L cloud − R cloud ) / R cloud 135 ◦ 10 π/ 2 90 ◦ 45 ◦ 0.0 0.2 0.4 0.6 0.8 1.0 30 ◦ 60 ◦ 120 ◦ 150 ◦ f kep φ 0 10 2 –45 ◦ 10 – π/ 2 –90 ◦ β 1 –135 ◦ 10 − 1 – π 0 π/ 4 π/ 2 3 π/ 4 π 0.0 0.3 0.6 0.9 θ α

Disruption Acceleration Rotation Conclusion Making this Useful 10 2 π ( L cloud − R cloud ) / R cloud 135 ◦ 10 π/ 2 90 ◦ 45 ◦ 0.0 0.2 0.4 0.6 0.8 1.0 30 ◦ 60 ◦ 120 ◦ 150 ◦ f kep φ 0 10 2 –45 ◦ 10 – π/ 2 –90 ◦ β 1 –135 ◦ 10 − 1 – π 0 π/ 4 π/ 2 3 π/ 4 π 0.0 0.3 0.6 0.9 θ α

Disruption Acceleration Rotation Conclusion Making this Useful 10 2 π ( L cloud − R cloud ) / R cloud 135 ◦ 10 π/ 2 90 ◦ 45 ◦ 0.0 0.2 0.4 0.6 0.8 1.0 30 ◦ 60 ◦ 120 ◦ 150 ◦ f kep φ 0 10 2 –45 ◦ 10 – π/ 2 –90 ◦ β 1 –135 ◦ 10 − 1 – π 0 π/ 4 π/ 2 3 π/ 4 π 0.0 0.3 0.6 0.9 θ α

Disruption Acceleration Rotation Conclusion Future Evolution of G and G a testable prediction? 150 120 10 − 1 110 100 100 ω a Ω 50 90 10 − 2 80 0 130 1900 1950 2000 2050 2100 1.0 time (JD) 120 0.9 110 100 e i 0.8 90 0.7 80 1900 1950 2000 2050 2100 1900 1950 2000 2050 2100 time (JD) time (JD)

Disruption Acceleration Rotation Conclusion Summary Magnetized Clouds Accretion Flow � Given enough assumptions, � Tangled magnetic fields G and G can be used to internal to the clouds can constrain properties of the inhibit disruption by shear accretion flow in the galactic instabilities. center. � Magnetic fields external to the � If it works, only constraint at cloud can enhance the drag intermediate radii. force, strongly coupling clouds to their environment. � Find an orientation for the rotation axis consistent with � Depends on the internal EHT determinations at structure of clouds; need to smaller scales. know how they formed to predict future evolution. � Please keep following G!