Radiation Pressure Supported Starburst Disks & AGN Fueling

Todd ThompsonUC Berkeley

With Eliot Quataert & Norm Murray

Evidence for Feedback: Winds

M82 (Subaru)

NGC 1569 (HST)

Regulation of star formation

on galactic scales.

Interactions, Mergers Star Formation

NGC 4038/4039 (HST)

ULIRGs

Borne et al. (2000)

Disk-like kinematics

Star formation ~102-3 M/yr

<n>~103-4

cm-3

~100 pc scales

The Standard Lore:Energy Deposition by Supernovae

Strickland & Stevens (2000)

Collective effects of supernovae regulate the ISM and drive a hot thermal wind.

McKee & Ostriker (1977)Chevalier & Clegg (1985)de Young & Heckman (1994)

Efficiency may be very low in the high-density ISM of starburst galaxies.

A New Model: Radiation Pressure• Starburst or AGN photons are absorbed and scattered

by dust grains (UV~100-1000 cm2 g-1).

• Dust is collisionally coupled to gas:• Efficient feedback mechanism: couples to cold and

dusty component, most of the mass.• Large-scale winds: Starbursts are near their

“Eddington” limit (Murray, Quataert, Thompson 2005)

• In ULIRGs, the ISM is optically thick to re-radiated IR on ~100 pc scales - radiative diffusion.

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λ ≈10pc a0.1ρ 3n1−1

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( ˙ M W / ˙ M *) ~ (10−3c /2σ ) ~ 1

Starburst Disks• Marginal stability, self-regulation: Toomre Q~1.

• Vertical hydrostatic equilibrium:

• Star formation:

• Radiative diffusion:

• Accretion ( or m):

• Modified Schmidt Law:

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Q =κ Ωcs

πGΣg

~Ω2

2πGρ⇒ ρ ~

Ω2

2πGQ

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F = σ SBTeff4 = (1/2)ε ˙ Σ *c

2

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p ≈ ρh2Ω2 ∝ Σg2

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T 4 ≈τ IRTeff4 ∝κΣg

˙ Σ *

Sirko & Goodman (2003) Thompson, Quataert, & Murray (2005)

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˙ Σ * ∝ Σg2 /τ IR ∝ Σg /κ

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˙ M (r) = ˙ M out − 2π rRout

r

∫ ˙ Σ * dr

TheRosseland Mean Opacity

Dust sublimates! Tsub ~ 1000 K

At Rout, if

then all of the gas is consumed in star formation on the scale Rout.

Equivalently,

Bifurcation: Starburst vs. AGN

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˙ M (r)€

˙ M *(r)

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τAdv > τ *

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˙ M out < ˙ M crit

Bifurcation: Starburst vs. AGN

At Rout, if

then the gas can propagate to small radii. It passes through the ``opacity gap’’ and fuels a bright central AGN.

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τAdv < τ *

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˙ M out > ˙ M crit

Bifurcation: Starburst vs. AGN

Bifurcation: Starburst vs. AGN

Very strong

in the opacity gap yields vertical structure withh/r~1.

Origin of nuclear obscuration in some AGN? Winds? NLR?

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dκ /dz

Bifurcation: Starburst vs. AGN

AGNReprocessing?

The Galactic Center: A Nuclear Starburst?

The opacity gap generates a sharp peak in the star formation rate at ~0.1 pc for our galactic center.

Levin & Beloborodov (2003)Genzel et al. (2003)

Summary• Radiation pressure

– can dominate feedback in the optically thick regions of starbursts.– couples to the cold dusty component, most of the mass.– can support the marginally-stable starburst disk.

• Disk models (given , or m, Rout, MBH, fg)– predict starburst structure:– are in good agreement with observations (local & high-z ULIRGs).– fuel bright AGN without violating observational limits.– predict strong bifurcation between starburst dominated

& AGN dominated solutions.– predict a nuclear starburst on ~1 pc scales (opacity gap).– predict qualitative change in the Schmidt Law:

• Radiation pressure can drive large-scale mass-loaded winds: sets Faber-Jackson, M-, & maximum L of galaxies & BHs.

Thompson, Quataert, Murray (2005) Murray, Quataert, & Thompson (2005)

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T(r), Teff (r), F(r), η (r), ρ(r), ˙ Σ *(r), cs(r)

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˙ Σ * ∝ Σg2 /τ IR ∝ Σg /κ

The End