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Abstract
We study the disc-corona interaction in different galactic environments through parsec-resolution hydrodynamical simulations. We find that this interaction could trigger the condensation of a fraction of hot coronal gas but the efficiency of this phenomenon is significantly reduced at increasing coronal temperature. - takes place at the interface - cold metal-rich gas mixes with low-Z hot gas - the mixing can cause the cooling of the hot gas (Marinacci et al., 2010)

Context
Interaction between galactic fountain and corona :
CORONA

INTERFACE

DISC

Hydrodynamical simulations
Fountain cloud in motion through the hot coronal gas


Including isotropic classic thermal conduction (Spitzer 1962)

Results (I)

F

cond

=-f Sp T

5/ 2

T

EFFECT OF THERMAL CONDUCTION
Fig.2 : Evolution of mass of cold gas ( T < 10 4.3 K ) with time for two simulations with coronal tem6 perature 2в10 K : one without thermal conduction and one with thermal conduction. The mass of cold gas increases with time because more and more coronal gas cools down in the wake.

with 10% efficiency f = 0.1 (Narayan & Medvedev, 2001) + saturation (Dalton & Balbus 1993)


Including radiative CIE cooling function (Sutherland & Dopita 1993)
CONDENSATION
2 в 10
6

1.0 0.5

y [kpc]

0.0 -0.5

T [K]

v0

EVAPORATION

t = 0 Myr -1.0 1.0 0.5 0.0 1.0 2.0 3.0 0.0 1.0 2.0

t = 20 Myr 3.0
10
4

y [kpc]

CONDENSATION WINS!
\ t = 40 Myr t = 60 Myr 2.0 3.0 x [kpc] 4.0 2.0 3.0 x [kpc] 4.0

Thermal conduction slows down the condensation of coronal gas but can not inhibit it.

0.0 -0.5 -1.0

Results (II)

Fig.1 : Temperatures snap-shots of a 2D hydrodynamical simulation after 0, 20, 40 and 60 Myr. The 6 coronal temperature is 2в 10 K . The simulations were performed by ATHENA code (Stone et al., 2008) with a resolution of 2 pc.

Coronal gas cools here!

CORONAL CONDENSATION vs CORONAL TEMPERATURE
Fig.3 : Evolution of mass of cold gas ( T < 10 4.3 K ) with time for four different values of coronal 6 temperature ( 1, 2, 4, 8 в 10 K ) .

MIXING : TURBOLENT WAKE CORONA CONDENSATION ?


CLOUD EVAPORATION ?

T

cor

2 в 10 6 K

Significant increase of the mass of cold gas

Does the coronal condensation efficiency depend on the coronal temperature?

T

cor

8 в 106 K

T cor M
Table 1 : Initial parameters of our simulations. The cloud density is calculated assuming pressure equilibrium between the cloud and the corona. The cloud radius is the typical size of the Intermediate Velocity Cloud.

2/3 vir

No condensation or evaporation

The higher the galaxy virial mass, the higher the coronal temperature the lower the coronal gas condensation.

Quenching of star-formation ?
References
Dalton W. W., Balbus S. A., 1993, ApJ, 404, 625; Marinacci F., Binney J., Fraternali F., et al., 2010, MNRAS, 404, 1464; Narayan R., Medvedev M.V., 2001, ApJ, 562, L129; Spitzer L., 1962, Physics of Fully Ionized Gases, Interscience, New York; Stone J. M., Gardiner T. A., Teuben P., et al., 2008, ApJS, 178, 137; Sutherland R. S., Dopita M. A., 1993, ApJS, 88, 253
Contacts Email : lucia.armillotta@unibo.it Telephone : (0039) 051 2095306