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