Studying the roots of starburstdriven galactic winds

1
On the hydrodynamics of the matter re-inserted
within Superstellar Clusters.
Wunsch et al 2007 AA 471, 579 Silich et al 2007
ApJ 669, 952 Tenorio-Tagle et al 2007 ApJ 568,
1196 Wunsch et al 2008 arXiv08051380
Guillermo Tenorio-Tagle (INAOE)?
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Superstellar clusters (SSC) young globular
clusters
The new unit of star formation
Ho 1997, Kobulnicky Johnson 1999, Johnson
etal 2001, Colina etal 2002, Larser Richtler
2000, OConnell 1995, De Gries 2007, Smith et al
2005, Melo et al. 2005, etc.
Westmoquette, Smith, Gallagher UCL/Univ. of
Wisconsin Press Release
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SSC Properties
Half light radius 3 pc - 10 pc 10
Msol ltMssclt few 10 Msol gt several
thousands massive stars

Melo et al. 2003, ApJ 619, 270
5
6
3
On the hydrodynamics of the matter reinserted
within SSCs.
1. Super Star Cluster winds
The prototype model for SSC winds (Chevalier
Clegg 1985) is based on the assumption that
massive stars are equally spaced within the SSC
volume. The kinetic energy deposited by massive
stars is completely thermalized via random
collisions of individual stellar winds and SN
ejecta, within the cluster volume. This
generates the large central overpressure that
accelerates the ejected matter and eventually
blows it out of the star cluster in the form of a
high velocity outflow the star cluster wind.

Rsc
Star cluster
In the adiabatic case three parameters define the
distributions of the outflowing gas velocity,
density, temperature and thermal pressure.
These are The energy and mass deposition rates
Lsc and Msc, and the star cluster radius Rsc.
Free Wind

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The resultant distributions of density,
temperature and velocity.
R_sc 10pc
V
8
-2
Rho
r
V Km/s
Density
Velocity
R (pc)?
R (pc)?
In the adiabatic case, the wind parameters
approach their asymptotic values at large radii
(R gtgt Rsc) .
-4/3
r
T
All of these solutions have the stagnation point
at the center of the SSC.
Temperature
R (pc)?
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The impact of radiative cooling
HOWEVER If instead of an adiabatic flow, one
allows for radiative cooling, the more energetic
or more massive the SSC, the more that
radiative cooling impacts on the resultant
winds.
Threshold line
Lsc

Rsc (pc)?
Strongly radiative winds
Rsc 3 pc
Negative feedback from SSCs
Log T
Quasi-adiabatic winds
Silich et al 2004 ApJ 610, 226
R (pc
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The bimodal hydrodynamic solution
V km/s
Rsc 10 pc
GTT, R. Wunsch, S. Silich J. Palous 2007 ApJ
658, 1196
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Positive feedback
For more energetic or more massive the SSCs,
above the threshold line, a fraction of the
deposited energy is immediately radiated away
from the densest central regions.
Threshold line
Lsc
Negative feedback

Rsc (pc)?
This causes the stagnation radius to move
towards the cluster surface, leading to a
bimodal solution. in these cases the outer
regions produce a stationary wind while the
matter deposited in the central regions
accumulates and becomes ready to participate in
further episodes of star formation. gtgt Strong
positive feedback!!!!!!
ApJ 568,1196
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Conclusions Clusters above the threshold line
log Lsc/Lcrit
enter the catastrophic cooling regime and cause
a bimodal solution
The results are shown in these universal
diagrams ApJ 2007
Rst/Rsc
Strong positive star formation feedback in
clusters well above the threshold line ie.
further generations of star formation within the
SSC volume and with the matter returned by winds
and SNe. gtwhy SSC do not disolve gtchemical
evolution of galaxies gtmass - metallicity
relation
Min
Min,out /Msc
Mout
Log Lsc/Lcrit
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• The location of the Threshold
• Line depends on the heating
• Efficiency (HE).
• Radiative cooling may be
• enhanced within the SSC
• volume due to a larger metal
• abundance of the ejected
• material or to the proximity of
• the exploding sources.

HE 1
HE .1
Z/Zsol
The heating efficiency defines the fraction of
the mechanical energy due to winds and SNe that
remains available, after thermalization, to
power the SSC wind.
Time Myr
10
M82-A1 (Smith et al 2005) M 1.3 x 106
Msol Age 6 Myr Radius 3pc HII region radius
4.5 pc HII region mass 5000 Msol gt poor
heating efficiency and A high pressure ISM
HE
The outflow velocity
Stellar density (100 Msol/pc-3)?
Rst

• Conclusion A low HE implies
• Slower winds
• Smaller Mout
• Bimodal solution
• Positive feedback

Rsc
RHII
Rcool
Rsh
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Mujer respirando por los pies
por Yolanda Tenorio
Tagle, 2006
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