Dusty winds and the Resonant Drag Instability Jono Squire - - PowerPoint PPT Presentation

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Dusty winds and the Resonant Drag Instability Jono Squire - - PowerPoint PPT Presentation

Jan 22, 2023 424 likes •985 views

Dusty winds and the Resonant Drag Instability Jono Squire GalFresca With Phil Hopkins Squire+Hopkins arXiv:1706.05020 + Stefania Moroianu (Cambridge) Eric Moseley (Caltech) Hopkins+Squire arXiv:1707.02997 RDI Basics GAS RDI Basics

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SLIDE 1

Dusty winds

and the

Resonant Drag Instability

Jono Squire — GalFresca

With Phil Hopkins

Stefania Moroianu (Cambridge) Eric Moseley (Caltech)

+

Squire+Hopkins arXiv:1706.05020 Hopkins+Squire arXiv:1707.02997

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SLIDE 2

GAS

RDI Basics

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SLIDE 3

GAS

RDI Basics

DUST

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SLIDE 4

GAS

RDI Basics

speed wdrift DUST

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SLIDE 5

GAS

RDI Basics

speed wdrift DUST

Gas drag on dust

Fdust

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SLIDE 6

GAS

RDI Basics

speed wdrift DUST

Gas drag on dust

Fdust

Dust backreaction on gas

Fgas

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SLIDE 7

RDI Basics

Wave in the gas

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SLIDE 8

wdrift = vdust − ugas = wave speed?

RDI Basics

Wave in the gas

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SLIDE 9

wdrift = vdust − ugas = wave speed?

RDI Basics

Wave in the gas

Wave is stationary in the dust frame — resonance

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SLIDE 10

wdrift = vdust − ugas = wave speed?

RDI Basics

Wave in the gas

Wave is stationary in the dust frame — resonance

Instability

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SLIDE 11

wdrift = vdust − ugas = wave speed?

RDI Basics

Wave in the gas

Wave is stationary in the dust frame — resonance

Instability

±iµ1/2 h (ξL

FT (1) ρd ) (kT D−1 dragCvξR F)

i1/2

γ =

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SLIDE 12

wdrift = vdust − ugas = wave speed?

RDI Basics

Wave in the gas Dust to gas mass ratio

Wave is stationary in the dust frame — resonance

Instability

±iµ1/2 h (ξL

FT (1) ρd ) (kT D−1 dragCvξR F)

i1/2

γ =

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SLIDE 13

wdrift = vdust − ugas = wave speed?

RDI Basics

Wave in the gas Dust to gas mass ratio Fluid modes

Wave is stationary in the dust frame — resonance

Instability

±iµ1/2 h (ξL

FT (1) ρd ) (kT D−1 dragCvξR F)

i1/2

γ =

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SLIDE 14

wdrift = vdust − ugas = wave speed?

RDI Basics

Wave in the gas Dust to gas mass ratio Coupling of dust to gas Fluid modes

Wave is stationary in the dust frame — resonance

Instability

±iµ1/2 h (ξL

FT (1) ρd ) (kT D−1 dragCvξR F)

i1/2

γ =

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SLIDE 15

wdrift = vdust − ugas = wave speed?

RDI Basics

Wave in the gas Dust to gas mass ratio Coupling of dust to gas Drag on the dust Fluid modes

Wave is stationary in the dust frame — resonance

Instability

±iµ1/2 h (ξL

FT (1) ρd ) (kT D−1 dragCvξR F)

i1/2

γ =

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SLIDE 16

wdrift = vdust − ugas = wave speed?

RDI Basics

Wave in the gas Dust to gas mass ratio Coupling of gas to dust Coupling of dust to gas Drag on the dust Fluid modes

Wave is stationary in the dust frame — resonance

Instability

±iµ1/2 h (ξL

FT (1) ρd ) (kT D−1 dragCvξR F)

i1/2

γ =

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SLIDE 17

RDI Basics

Gas wave can be:

wdrift > cs

Squire+Hopkins arXiv:1706.05020

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SLIDE 18

RDI Basics

Gas wave can be:

  • Sound wave — RDI if wdrift > cs

Squire+Hopkins arXiv:1706.05020

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SLIDE 19

RDI Basics

Gas wave can be:

  • Sound wave — RDI if
  • MHD waves (slow/fast waves)

wdrift > cs

Squire+Hopkins arXiv:1706.05020

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SLIDE 20

RDI Basics

Gas wave can be:

  • Sound wave — RDI if
  • MHD waves (slow/fast waves)
  • Buoyancy oscillations

wdrift > cs

Squire+Hopkins arXiv:1706.05020

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SLIDE 21

RDI Basics

Gas wave can be:

  • Sound wave — RDI if
  • MHD waves (slow/fast waves)
  • Buoyancy oscillations
  • Epicyclic oscillations

wdrift > cs

Squire+Hopkins arXiv:1706.05020

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SLIDE 22

RDI Basics

Gas wave can be:

  • Sound wave — RDI if
  • MHD waves (slow/fast waves)
  • Buoyancy oscillations
  • Epicyclic oscillations
  • …….

wdrift > cs

Squire+Hopkins arXiv:1706.05020

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SLIDE 23

RDI Basics

Gas wave can be:

  • Sound wave — RDI if
  • MHD waves (slow/fast waves)
  • Buoyancy oscillations
  • Epicyclic oscillations
  • …….

wdrift > cs

This talk

Squire+Hopkins arXiv:1706.05020

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SLIDE 24

Source of wdrift

Radiation pressure on dust drives winds:

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SLIDE 25

Source of wdrift

Radiation pressure on dust drives winds: AGN

wdrift ∼ 100cs

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SLIDE 26

Source of wdrift

Radiation pressure on dust drives winds: AGN

wdrift ∼ 100cs

Starbursts/GMCs/star forming disks

wdrift ∼ 10cs

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SLIDE 27

Cool star winds

wdrift ∼ cs

Radiation pressure on dust drives winds:

Source of wdrift

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SLIDE 28

Cool star winds

wdrift ∼ cs

Supernovae ejecta

wdrift ∼ cs

Radiation pressure on dust drives winds:

Source of wdrift

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SLIDE 29

Protoplanetary disks

wdrift ⌧ cs

Pressure support of gas drives wdridt in

Source of wdrift

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SLIDE 30

Protoplanetary disks

wdrift ⌧ cs

But lots of other waves… 
 Epicycles (streaming instability), 
 Brunt-Vaisala, MHD, Hall MHD…

Youdin & Goodman (2005)

Pressure support of gas drives wdridt in

Source of wdrift

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SLIDE 31

Acoustic RDI (sound waves) from radiation pressure

Hopkins+Squire arXiv:1707.02997

dv dt = −v − ugas ts + arad

Dust equation

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SLIDE 32

Acoustic RDI (sound waves) from radiation pressure

Hopkins+Squire arXiv:1707.02997

dv dt = −v − ugas ts + arad

Radiative acceleration

Dust equation

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SLIDE 33

Acoustic RDI (sound waves) from radiation pressure

Hopkins+Squire arXiv:1707.02997

dv dt = −v − ugas ts + arad

Radiative acceleration Dust drag

Dust equation

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SLIDE 34

Acoustic RDI (sound waves) from radiation pressure

Hopkins+Squire arXiv:1707.02997

dv dt = −v − ugas ts + arad

Radiative acceleration Dust drag

Dust equation ts determined by grain size, gas density (Epstein drag)

big grains free stream small grains stop quickly

arad determined by Fλ, λ/Rd, md

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SLIDE 35

Dust drags gas

wdrift ∼ arad ts

dugas dt = ρd ρgas ugas v ts rp

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SLIDE 36

Dust drags gas

wdrift ∼ arad ts

1 2 3 4 5 6 7 0.5 1.0 1.5 2.0 2.5 3.0 3.5

v ugas ts wdrift Equilibrium with constant acceleration

dugas dt = ρd ρgas ugas v ts rp

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SLIDE 37

RDI condition — dust streaming matches wave

wdrift cos(θ) = cs

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SLIDE 38

RDI condition — dust streaming matches wave

wdrift cos(θ) = cs

Sound wave Dust streaming θ

wdrift = 2cs

θ = 60

E.g.,

Dust “sees” a stationary wave

cs wdrift

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SLIDE 39

RDI condition — dust streaming matches wave

ω ⇡ kcs + µ1/2 1 + i 2 k1/2 s cs htsi

  • 1

η 1 + ζ

  • Growth rate keeps

increasing with k

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SLIDE 40

(maximum over all k)

10 1 0.1 0.01 0.001 (no resonance)

Instability is fastest growing at resonant angle but still exists for subsonic ws

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SLIDE 41

Acoustic RDI is robust:

  • Arbitrary drag law (Epstein, Coulomb etc.,) and dust size
  • Any streaming velocity
  • Arbitrary gas equation of state
  • Any dust-to-gas mass ratio
  • Gas pressure support
  • Spectrum of grain sizes

ω ⇡ kcs + µ1/2 1 + i 2 k1/2 s cs htsi

  • 1

η 1 + ζ

  • see Hopkins+Squire arXiv:1707.02997
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SLIDE 42

Nonlinear evolution — what happens?

Stefania Moroianu (Cambridge) Eric Moseley (Caltech)

with GIZMO periodic with 1283 gas/dust

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SLIDE 43

Resonant mode matters even in nonlinear turbulence

Time

x z

drift

x y

drift

wdrift ≈ 3cs cos θ = cs wdrift

ρd ρg = 0.01

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SLIDE 44

Resonant mode matters even in nonlinear turbulence

Time

x z

drift

x y

drift

wdrift ≈ 3cs cos θ = cs wdrift

ρd ρg = 0.01

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SLIDE 45

x z

drift

x y

drift

wdrift ≈ 10cs

Dust can decouple completely! cos θ = cs wdrift

ρd ρg = 0.01

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SLIDE 46

x z

drift

x y

drift

wdrift ≈ 10cs

Dust can decouple completely! cos θ = cs wdrift

ρd ρg = 0.01

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SLIDE 47

Range of grain sizes

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SLIDE 48

Range of grain sizes

  • Does the instability exist? (Yes!)
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SLIDE 49

Range of grain sizes

  • Does the instability exist? (Yes!)
  • Effect of dust size spectrum, e.g.,

dM d ln Rd ∼ R0.5

d

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SLIDE 50

Range of grain sizes

  • Does the instability exist? (Yes!)
  • Effect of dust size spectrum, e.g.,
  • Acceleration

dM d ln Rd ∼ R0.5

d

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SLIDE 51

Range of grain sizes

  • Does the instability exist? (Yes!)
  • Effect of dust size spectrum, e.g.,
  • Acceleration

dM d ln Rd ∼ R0.5

d

arad ∼ const. λ > Rd wdrift ∼ R1/2

d

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SLIDE 52

Range of grain sizes

  • Does the instability exist? (Yes!)
  • Effect of dust size spectrum, e.g.,
  • Acceleration

dM d ln Rd ∼ R0.5

d

arad ∼ const. λ > Rd wdrift ∼ R1/2

d

arad ∼ 1/Rd λ < Rd wdrift ∼ const.

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SLIDE 53

x z

drift

x y

drift

Big grains Medium Small

DUST GAS GAS DUST

wdrift ≈ 1.5cs

ρd ρg = 0.1

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SLIDE 54

x z

drift

x y

drift

Big grains Medium Small

DUST GAS GAS DUST

wdrift ≈ 1.5cs

ρd ρg = 0.1

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SLIDE 55
  • Dust-driven winds/outflows are likely unstable to RDI
  • Can grow very fast (formally 𝛿→∞ as k→∞)
  • Drives large dust-to-gas fluctuations and turbulence
  • Important for AGN, star-forming regions, cool stars, SNe

ejecta?

  • Implications for grain collisions/growth?

Conclusions