Ionization%20composition%20of%20dwarf%20galaxies

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Ionization composition of dwarf galaxies
Evgenii Vasiliev Institute of Physics, Southern
Federal University, Rostov on Don
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background
observations of metals in blue compact
dwarfs Aloisi et al 2003 Zw18 NI, OI, FeII,
SiII Lebouteiller et al 2004 Zw 36 CII, NI,
OI, SiII, FeII, CIII, NII, FeIII, OVI
Vilchez Iglesias-Paramo 2003 - 22 BCDs
photoizined gas in DM minihalos Gnat Sternberg
2004 neutral cores OI, NI, CII, SiII ionized
shielding envelopes CIV, NV, OVI
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calculations of the cooling rates of
astrophysical plasma

• collisional ionization equilibrium (CIE) Cox
  Tucker 1969, Raymond et al. 1976, Shull van
  Steenberg 1982, Gaetz Salpeter 1983,
  Sutherland Dopita 1993, Benjamin et al. 2001
• non-equlibrium (time-dependent) radiative
  cooling Kafatos 1976, Shapiro Moore 1976,
  Edgar Chevalier 1986, Schmutzler Tscharnuter
  1993, Sutherland Dopita 1993, Gnat
  Sternberg 2007

strong difference between equlibrium and
non-equilibrium cooling rates ionization states
Gnat Sternberg 2007
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calculations of the cooling rates of
astrophysical plasma
presence of UV radiation
equlibrium
strong suppression of the cooling rates of
HHe plasma Efstathiou (1992) enriched gas
Wiersma et al. (2008) - EQ
equlibrium non-equilibrium a) low
metallicity b) high ionizing flux c) low
density or b) c) high ionization
parameter
EV, in preparation
non-equilibrium collisional rates
(dash) equilibrium photo rates (dot) non-equilibri
um photo rates (solid)
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equlibrium or non-equilibrium example
DWs number densities 10-3 10-2 cm-3 low
flux transition from EQ to NEQ
EQ NEQ
NEQ collisional n 10-4 cm-3 n 10-3 cm-3 n
10-2 cm-3
non-equilibrium collisional state black
solid non-equilibrium photo state - color
EV et al., in preparation
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atomic data and model description

• the ionization and thermal evolution of a
  lagrangian element
• optically thin for external ionizing radiation
• all ionization states of the elements H, He, C,
  N, O, Ne and Fe
• major processes
• photoionization (Verner et al. 1996,
  Vener Yakovlev 1995, Kaastra Mewe 1993)
• collisional ionization (Voronov 1997)
• radiative and dielectronic recombination
  (Shull van Steenberg 1982, Mazzotta et al.
  1998)
• charge tranfer in collisions with hydrogen and
  helium atoms and ions (Arnaud Rothenflug
  1985, Kingdon Ferland 1996)

total cooling and heating rates are calculated
using the photoionization code CLOUDY as
subroutine
solve a set of 68 coupled equations
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ionizing background
10x 4x 2x 1x
ionizing radiation local universe
extragalactic background z 0 (Haardt Madau
1996, 2001)
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carbon ionization states example
1x 2x 4x 10x
non-equilibrium collisional state -
black non-equilibrium photo state - color
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carbon ionization states example
1x 2x 4x 10x
non-equilibrium collisional state -
black non-equilibrium photo state - color
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ionization state ratios
NEQ collisional Z 0 Z 0 Z -1 Z -3
n 10-4 cm-3 - dot n 10-3 cm-3 - solid n
10-2 cm-3 - dash
ionizing radiation extragalactic background z
0 (Haardt Madau 1996, 2001)
decrease density
non-equilibrium collisional state -
black non-equilibrium photo state - color
Neq Eq
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ionization state ratios
Vilchez Iglesias-Paramo 2003
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ionization state ratios
temperature
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conclusion future

• the strong difference between equilibrium and
  non-equilibrium ionization states ( cooling
  rates) can be important for modeling ionic
  composition in dwarf galaxies
• study ionic ratios for different stellar
  population spectra
• incorporation of ionic state cooling rate
  calculations into gas dynamics.

thank you!!!
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conclusion future
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carbon ionization states example
1x 2x 4x 10x
non-equilibrium collisional state -
black non-equilibrium photo state - color
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ratio of cooling rates
r non-equilibrium rate / equilibrium rate
gas density
metallicity
power-law, a 1
flux
log T
redshift
extra-galactic back-d