Frenk, Bauch Cole, Lacey
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Frenk, Bauch Cole, Lacey Wang 2000; Chandra obs of NGC4632. At small (galactic) scales a number of complex processes are crucial in determining the observed properties The radiative cooling of gas in galaxies The star formation from such cooled gas The evolution of the stellar population The feedback from Supernovae reheating part of the cooled gas
description
Wang 2000; Chandra obs of NGC4632. Frenk, Bauch Cole, Lacey. Hydrostatic Equilirium of Gas in DM potential wells. Radiative Cooling: I Collisional Excitation. v. T ~ 10 5 - 10 8 K. j. g. i. v. hv=E ij. Condition: En. of Elettrons E ≈ KT > D E lu. Collision rate. - PowerPoint PPT Presentation
Transcript of Frenk, Bauch Cole, Lacey
Frenk, Bauch
Cole, Lacey
Wang 2000; Chandra obs of NGC4632.
At small (galactic) scales a number of complex processes are crucial in determining the observed properties
The radiative cooling of gas in galaxies The star formation from such cooled gas The evolution of the stellar population The feedback from Supernovae reheating part of the cooled gas
32/12 RTnL gasX
2r
GM
d
dp
Hydrostatic Equilirium of Gas
in DM potential wells
2
3c8
vir2
km/s 10K 10 )(r
2
1
vvmkT cpv
T ~ 105 - 108 Kv
i
j
Condition: En. of Elettrons E ≈ KT > Elu
Radiative Cooling: I Collisional Excitation
Collision rate
vennq ijkT
E
elij
ij
2 ~ 1/v 2 ( Coulomb focussing) x Quantum factors
vwv
nenvfdvq iji
ikT
E
eij
ij
11
)(2
Number of electrons above the threshold
v hv=Eij
kT
mv
evkT
mvf 22
2/3 2
2
4)(
13-2/1
6 cm 1063.8
sh
wT
e
Volumetime
LossEnergyij
i
ijKT
Eij
exp(-E/T)
T1/2
Log T
Log
lulule hqnnL
kT
eNNL
kT
h
ie
At temperatures T>106 K (DM haloes wth M>1013 Mʘ) the gas is completely ionized. The emission is due to bremsstrahlung from free electrons
Radiative Cooling: II Free-Free Emission
kT
eNNL
kT
h
ie
TNNdLVolumetime
LossEnergyie
T1/2
Log
Log T6
T1/2
Log
Log T6
exp(-E/T)
T1/2
Log T
exp(-E/T)
T1/2
Log T
E for Hydrogen E for Helium
+ +
= Volumetime
LossEnergyNN ie
Cooling Function
)()(m
(r)
2
32
p Trn
kT
e
gascool
yrsa
aH 108.9 9
Hcoolcoolr for which regions of radiusouter
To be compared with
A fraction mcool of the available gas bar M is able to radiatively cool
In high-density (inner) regions the cooling time is shorter than the galaxy survival time
Cooling Radius
drrrMm gascool )( 4)( 2r
0
cool
ClustersGalaxies
Cores of galaxy Clusters
32/12 RTnL gasX
Clusters
Galaxies
Rees & Ostriker 1977
Mo, Mao, White 1997
Assume that, durung collapse, the ratio of the ratio is conserved
gas
DM
Assuming an exponential Surf. Dens.
)/exp()( 0 dRRR
Assuming centrifugal balance
dRRRMVJ cgas2)()(2
)(2
1MR
m
jR vir
gas
gasd
Disks
JJj gasgas /
Jgas = Gas Angul. Mom.
J = DM Angul. Mom.
08.001.0
/ 2/512/1
MGJEJJ circ
cV rMJ circ
22
22cMV
r
GME
For particles in circular orbits
2/12/5G EMJ circ
DM angular momentum aquired from tidal torques due to surrounding perturbations
med=0.04=0.53
Warren et al.92
