Gas mixing and Star formation by Gas mixing and Star formation by

shock waves and turbulenceshock waves and turbulence

Claudio MelioliClaudio Melioli

Elisabete M. de Gouveia Dal PinoElisabete M. de Gouveia Dal Pino

(IAG-USP)(IAG-USP)

IntroductionIntroduction

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 waveSN shock wave

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

Adiabatic evolutionAdiabatic evolution

Radiative evolutionRadiative evolution

DensityDensity

VelocityVelocity

TemperatureTemperature

SuperbubbleSuperbubble

SNRs may interact each with the others

Energization of the ISM: T=10Energization of the ISM: T=1066, low densities, low densities

Winds from SB GalaxiesWinds from SB Galaxies

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

What is the Wind Engine ?What is the Wind Engine ?

SN explosionsSN explosions The effectiveness of the The effectiveness of the process depends on the process depends on the heating efficiency (HE) of heating efficiency (HE) of the SNe, i.e. on the fraction the SNe, i.e. on the fraction of SN energy which is of SN energy which is notnot radiated away.radiated away.

Detailed model to determine HE (Melioli & de Gouveia Dal Detailed model to determine HE (Melioli & de Gouveia Dal Pino, A&A, 2004)Pino, A&A, 2004)

E

c

SN

p

2

21

25

HE

SNSN

Shock waveShock wave SuperbubbleSuperbubble TurbulenceTurbulence

Star formation?Star formation?

Density increase?Density increase?

Galactic winds?Galactic winds?

Clumps by shock waveClumps by shock wave

Cold and dense filaments, clumps; Cold and dense filaments, clumps; increase of the ISM density by cloud ablationincrease of the ISM density by cloud ablation

Interactions between a shock wave and ISM inhomogentiesInteractions between a shock wave and ISM inhomogenties

Possible reduction of the gas outflowPossible reduction of the gas outflow

Steady state shock wave (wind) - 1 cloudSteady state shock wave (wind) - 1 cloud

ShockShockWaveWave

1.6 pc1.6 pc

Steady state shock wave (wind) - 3 cloudSteady state shock wave (wind) - 3 cloud

Star Formation by shock waveStar 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 instabilityJeans instability

Turbulence, shock waves

SNR Radius

Mj

50 pc

Radiative

Sedov

5.150,

2100,1200 SNRCC RTMM

5.250,

2100,1300 SNRCC RTMM

Jeans instability induced by SNRsJeans instability induced by SNRs

1200 MO

SNR - GMC interactionSNR - GMC interaction

RRcc=10 pc=10 pc

TTcc=100 K=100 K

n =10 cmn =10 cm-3-3

Mj=35000MΘ

SNR

Mj=1000MΘ

2 SNR2 SNR

= 10SB

3 SN3 SN

= 12SB

5 SN5 SN

= 60SB

100 pc

...in progress!...in progress!= SB

ConclusionsConclusions

Energization by SN explosions:Energization by SN explosions: OutflowOutflowStar formationStar formationMixingMixing

Turbulence and shock wave:Turbulence and shock wave:Trigger Star formationTrigger Star formationClumpsClumpsFilamentsFilaments

High SN rate:High SN rate:MixingMixingOutflow Outflow

Low SN rateLow SN rate SB continuous?SB continuous?

SB PropertiesSB Properties

Starburst GalaxiesStarburst Galaxies

- Gas rich- Gas rich- Intense star formIntense star form- O, B stars- O, B stars- SNs- SNs

SN explosionSN explosion

--RRSN SN ~~1010-3-3/yr/yr

-N-NSN SN ~0.01 M~0.01 M*(*(M)

-E ~10-E ~105151 erg erg

High star formation rateHigh star formation rate

-10% of gas in stars -10% of gas in stars -star -star burstburst--stellar clusterstellar cluster of few of few pcpc

SuperbubblesSuperbubbles

Hot gasHot gas:: T~10T~106-8 6-8 KKLow density: n~10Low density: n~10-2-2 cm cm-3-3

Dimensions: R~100-1000 pcDimensions: R~100-1000 pc

T= 1000 KT= 1000 Kn = 600 cmn = 600 cm-3-3 MMjj = 10 = 1055 M MOO

T= 4000 KT= 4000 Kn = 160 cmn = 160 cm-3-3 MMjj = 10 = 1066 M MOO

Gravitational collapse coupled to shearProtostellar winds and jetsMagnetorotational instabilitiesMassive starsExpansion of H II regionsFluctuations in UV fieldStellar windsSupernovae

2

-1 -3

2

26

51

2 10 erg s cm0.1 1 SNu

200 pc

15 kpc 10 erg

SN SN SN

g

SN SN

g SN

Ee

R H

R E

H

SNe appear hundreds or thousands of times more powerful SNe appear hundreds or thousands of times more powerful

than all other energy sourcesthan all other energy sources