Gas mixing and Star formation by shock waves and turbulence

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Gas mixing and Star formation by shock waves and
turbulence

• Claudio Melioli
• Elisabete M. de Gouveia Dal Pino
• (IAG-USP)

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Introduction
Most galaxies present supernova shock fronts
interacting with a cloudy interstellar medium.
These interactions can occur either at small
scales, between a single supernova remnant (SNR)
and a compact cloud or globule, or at large
scales, between a giant shell of a superbubble
and a molecular cloud. Particularly, in this
work we are interested to study the by-products
of SNR-clouds and SNR-SNR interactions in a
starburst ( ) system. The study of these SN
explosions and interactions is also relevant to
understand the evolution of the ISM, its
energization and the processes of outflow and
infall of the gas.
SB
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SN shock wave
A SNR will form only after the SN shock front
enter the Sedov phase.
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Adiabatic evolution
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Radiative evolution
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Density
Velocity
Temperature
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Superbubble
SNRs may interact each with the others
Energization of the ISM T106, low densities
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Winds from SB Galaxies
Gigantic bipolar super winds may emerge from the
galactic disk at high velocities into the
intergalactic medium
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What is the Wind Engine ?
The effectiveness of the process depends on the
heating efficiency (HE) of the SNe, i.e. on the
fraction of SN energy which is not radiated away.
SN explosions
HE
Detailed model to determine HE (Melioli de
Gouveia Dal Pino, AA, 2004)
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SN
Superbubble
Turbulence
Shock wave
Star formation?
Density increase?
Galactic winds?
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Clumps by shock wave
Interactions between a shock wave and ISM
inhomogenties
Cold and dense filaments, clumps increase of
the ISM density by cloud ablation
Possible reduction of the gas outflow
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Steady state shock wave (wind) - 1 cloud
1.6 pc
Shock Wave
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Steady state shock wave (wind) - 3 cloud
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Star Formation by shock wave
A giant molecular cloud may collapse and fragment
to form stars. Stellar winds and shock waves
from a supernova explosion may squeeze molecular
clouds and induce subsequent birth of stars which
otherwise may not have occurred. On the other
hand the agitation may be so violent as to
disperse the material, hindering further
star-forming activity.
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Jeans instability
Turbulence, shock waves
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Jeans instability induced by SNRs
Radiative
50 pc
Sedov
Mj
1200 MO
SNR Radius
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SNR - GMC interaction
SNR
Rc10 pc Tc100 K n 10 cm-3
Mj35000MT
Mj1000MT
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2 SNR
? 10?SB
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3 SN
? 12?SB
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5 SN
? 60?SB
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100 pc
? ?SB
...in progress!
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Conclusions
Outflow Star formation Mixing
Energization by SN explosions
Trigger Star formation Clumps Filaments
Turbulence and shock wave
Mixing Outflow
High SN rate
SB continuous?
Low SN rate
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SB Properties

• Starburst Galaxies
• - Gas rich
• Intense star form
• - O, B stars
• - SNs

High star formation rate -10 of gas in stars
-star burst -stellar cluster of few pc
SN explosion -RSN 10-3/yr -NSN 0.01 M(M?) -E
1051 erg
Superbubbles Hot gas T106-8 K Low density
n10-2 cm-3 Dimensions R100-1000 pc
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T 1000 K n 600 cm-3
Mj 105 MO
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T 4000 K n 160 cm-3
Mj 106 MO
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Gravitational collapse coupled to
shear Protostellar winds and jets Magnetorotationa
l instabilities Massive stars Expansion of H II
regions Fluctuations in UV field Stellar
winds Supernovae
SNe appear hundreds or thousands of times more
powerful than all other energy sources