Gas mixing and Star formation by shock waves and turbulence Claudio Melioli Elisabete M. de Gouveia Dal Pino (IAG-USP)

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

SN shock wave A SNR will form only after the SN shock front enter the Sedov phase.

Adiabatic evolution

Radiative evolution

Density Velocity Temperature

Superbubble SNRs may interact each with the others Energization of the ISM: T=10 6, low densities

Winds from SB Galaxies Gigantic bipolar super winds may emerge from the galactic disk at high velocities into the intergalactic medium

What is the Wind Engine ? SN explosions 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. Detailed model to determine HE (Melioli & de Gouveia Dal Pino, A&A, 2004) HE

SN Shock wave SuperbubbleTurbulence Star formation? Density increase? Galactic winds?

Clumps by shock wave Cold and dense filaments, clumps; increase of the ISM density by cloud ablation Interactions between a shock wave and ISM inhomogenties Possible reduction of the gas outflow

Steady state shock wave (wind) - 1 cloud ShockWave 1.6 pc

Steady state shock wave (wind) - 3 cloud

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.

Jeans instability Turbulence, shock waves

SNR Radius MjMj 50 pc Radiative Sedov Jeans instability induced by SNRs 1200 M O

SNR - GMC interaction R c =10 pc T c =100 K n =10 cm -3 M j =35000M Θ SNR M j =1000M Θ

2 SNR  = 10  SB

3 SN  = 12  SB

5 SN  = 60  SB

100 pc...in progress!  =  SB

Conclusions Energization by SN explosions: Outflow Star formation Mixing Turbulence and shock wave: Trigger Star formation ClumpsFilaments High SN rate: MixingOutflow Low SN rate SB continuous?

SB Properties Starburst Galaxies - Gas rich - Intense star form - O, B stars - SNs SN explosion -R SN ~10 -3 /yr -N SN ~0.01 M *( -N SN ~0.01 M *( M  ) -E ~10 51 erg High star formation rate -10% of gas in stars -star burst -stellar cluster of few pc Superbubbles Hot gas: T~ K Low density: n~10 -2 cm -3 Dimensions: R~ pc

T= 1000 K n = 600 cm -3 M j = 10 5 M O

T= 4000 K n = 160 cm -3 M j = 10 6 M O

Gravitational collapse coupled to shear Protostellar winds and jets Magnetorotational 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