Transcript Gas mixing and Star formation by shock waves and turbulence

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 (SB) 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.
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=106, 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
1
2
5
 p c 
2
2

HE 
E
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
Detailed model to determine HE (Melioli & de Gouveia Dal
Pino, A&A, 2004)
SN
Shock wave
Superbubble
Turbulence
Star formation?
Density increase?
Galactic winds?
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
Steady state shock wave (wind) - 1 cloud
1.6 pc
Shock
Wave
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
Jeans instability induced by SNRs
Radiative
50 pc
Mj
Sedov
1200 MO
SNR Radius
MC  1200M T
2
 C ,100
MC  1300M T
2
 C ,100
1.5
SNR ,50
R
2.5
SNR ,50
R
SNR - GMC interaction
SNR
Rc=10 pc
Tc=100 K
n =10 cm-3
Mj=35000MΘ
Mj=1000MΘ
2 SNR
= 10SB
3 SN
= 12SB
5 SN
= 60SB
100 pc
= SB
...in progress!
Conclusions
Energization by SN explosions:
Turbulence and shock wave:
High SN rate:
Low SN rate
Outflow
Star formation
Mixing
Trigger Star formation
Clumps
Filaments
Mixing
Outflow
SB continuous?
SB Properties
Starburst Galaxies
High star formation rate
- Gas rich
- Intense star form
- O, B stars
- SNs
-10% of gas in stars
-star burst
-stellar cluster of few pc
Superbubbles
SN explosion
Hot gas: T~106-8 K
Low density: n~10-2 cm-3
Dimensions: R~100-1000 pc
-RSN ~10-3/yr
-NSN ~0.01 M*(M)
-E ~1051 erg
T= 1000 K
n = 600 cm-3
Mj = 105 MO
T= 4000 K
n = 160 cm-3
Mj = 106 MO
Gravitational collapse coupled to shear
Protostellar winds and jets
Magnetorotational instabilities
Massive stars
Expansion of H II regions
Fluctuations in UV field
Stellar winds
 SNSN ESN
e
Supernovae
 Rg2 H
   

  2  1026 erg s -1 cm -3   SN  SN 
 0.1  1 SNu 
2
  ESN 
 200 pc  
  51



 H   15 kpc   10 erg 
Rg
SNe appear hundreds or thousands of times more powerful
than all other energy sources