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

SLIDE 1

Magnetized Gas Clouds in the Galactic Center

Mike McCourt, Ryan O’Leary, Ann-Marie Madigan, & Eliot Quataert

SLIDE 2

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

SLIDE 3

Dynamics of Magnetized Gas Clouds in Dilute Plasmas

SLIDE 4

Disruption Acceleration Rotation Conclusion

Background Li et al. 2013

“Cloud Crushing:”

tcrush ∼ ρcloud ρwind 1/2 Rcloud vwind

SLIDE 5

hydro t = 5 tcrush t = tstop

Σcloud /(ρcloud Rcloud)

1 0.1 0.01 0.001 0.0

SLIDE 6

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

SLIDE 7

mhd 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

SLIDE 8

Disruption Acceleration Rotation Conclusion

aside: initial conditions matter

SLIDE 9

Disruption Acceleration Rotation Conclusion

Magnetically-Enhanced Drag Force

✽ ✽ ✽

t / tcrush distance / Rcloud

5 10 15 10 20 30 40 50 60 70 80

Hydro βwind = 10 βwind = 1 βwind = 0.1

SLIDE 10

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

SLIDE 11

Disruption Acceleration Rotation Conclusion

(Re-)Discovery of G

G G a . ± . . ± . e . ± . . ± . (Pfuhl et al. 2014)

SLIDE 12

Disruption Acceleration Rotation Conclusion

(Re-)Discovery of G

G G a . ± . . ± . e . ± . . ± . (Pfuhl et al. 2014)

SLIDE 13

Disruption Acceleration Rotation Conclusion

(Re-)Discovery of G

G G a . ± . . ± . e . ± . . ± . J . . (Pfuhl et al. 2014)

SLIDE 14

Disruption Acceleration Rotation Conclusion

(Re-)Discovery of G

G G a . ± . . ± . e . ± . . ± . J . . i . ± . . ± . Ω . ± . . ± . ω . ± . . ± . (Pfuhl et al. 2014)

SLIDE 15

Disruption Acceleration Rotation Conclusion

(Re-)Discovery of G

G G a . ± . . ± . e . ± . . ± . J . . i . ± . . ± . Ω . ± . . ± . ω . ± . . ± . (Pfuhl et al. 2014)

SLIDE 16

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

— John Steinbeck

SLIDE 17

“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

SLIDE 18

vcloud vwind Fdrag

SLIDE 19

Disruption Acceleration Rotation Conclusion

A (too-)Simple Model

d2r dt2 = −GM• r r3 − ρbg( r) Mcloud ×

1 +

2 βM2

× C−1 · diag
R2

cloud, RcloudLcloud, RcloudLcloud

· (C ·

vrel)2 ρbg( r) = ρ0 r r0 −a Tbg( r) = GM• r

vbg(

r) = fkep GM• r 1/2 J × r J r

SLIDE 20

Disruption Acceleration Rotation Conclusion

Comparison with the Data

✽

vlos (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

SLIDE 21

✽

SLIDE 22

✽

SLIDE 23

Disruption Acceleration Rotation Conclusion

Making this Useful

θ φ

30◦ 60◦ 120◦ 150◦ –90◦ 90◦ π/4 π/2 3π/4 π –π –π/2 π/2 π

α β

0.0 0.3 0.6 0.9 10−1 1 10 102

fkep (Lcloud − Rcloud)/Rcloud

0.0 0.2 0.4 0.6 0.8 1.0 10 102

SLIDE 24

Disruption Acceleration Rotation Conclusion

Making this Useful

α β

0.0 0.3 0.6 0.9 10−1 1 10 102

fkep (Lcloud − Rcloud)/Rcloud

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◦ π/4 π/2 3π/4 π –π –π/2 π/2 π

SLIDE 25

Disruption Acceleration Rotation Conclusion

Making this Useful

α β

0.0 0.3 0.6 0.9 10−1 1 10 102

fkep (Lcloud − Rcloud)/Rcloud

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◦ π/4 π/2 3π/4 π –π –π/2 π/2 π

SLIDE 26

Disruption Acceleration Rotation Conclusion

Making this Useful

α β

0.0 0.3 0.6 0.9 10−1 1 10 102

fkep (Lcloud − Rcloud)/Rcloud

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◦ π/4 π/2 3π/4 π –π –π/2 π/2 π

SLIDE 27

Disruption Acceleration Rotation Conclusion

Making this Useful

α β

0.0 0.3 0.6 0.9 10−1 1 10 102

fkep (Lcloud − Rcloud)/Rcloud

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◦ π/4 π/2 3π/4 π –π –π/2 π/2 π

SLIDE 28

Disruption Acceleration Rotation Conclusion

Making this Useful

α β

0.0 0.3 0.6 0.9 10−1 1 10 102

fkep (Lcloud − Rcloud)/Rcloud

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◦ π/4 π/2 3π/4 π –π –π/2 π/2 π

SLIDE 29

Disruption Acceleration Rotation Conclusion

Making this Useful

α β

0.0 0.3 0.6 0.9 10−1 1 10 102

fkep (Lcloud − Rcloud)/Rcloud

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◦ π/4 π/2 3π/4 π –π –π/2 π/2 π

SLIDE 30

Disruption Acceleration Rotation Conclusion

Future Evolution of G and G

a testable prediction?

a 10−2 10−1 time (JD) e 1900 1950 2000 2050 2100 0.7 0.8 0.9 1.0 Ω 50 100 150 time (JD) i 1900 1950 2000 2050 2100 80 90 100 110 120 130 time (JD) ω 1900 1950 2000 2050 2100 80 90 100 110 120

SLIDE 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!