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Ionization composition of dwarf galaxies

Ionization composition of dwarf galaxies. Evgenii Vasiliev Institute of Physics, Southern Federal University, Rostov on Don. background. observations of metals in blue compact dwarfs Aloisi et al 2003 – Zw18: NI, OI, FeII, SiII

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Ionization composition of dwarf galaxies

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  1. Ionization composition of dwarf galaxies Evgenii Vasiliev Institute of Physics, Southern Federal University, Rostov on Don

  2. 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 • photoizinedgas in DM minihalos • Gnat & Sternberg 2004 • neutral cores: OI, NI, CII, SiII • ionized shielding envelopes: CIV, NV, OVI

  3. calculations of the cooling rates of astrophysical plasma • collisional ionizationequilibrium (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 coolingKafatos 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

  4. calculations of the cooling rates of astrophysical plasma presence of UV radiation equlibrium strong suppression of the cooling rates of H+He plasmaEfstathiou (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-equilibrium photo rates (solid)

  5. 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

  6. 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 CLOUDYassubroutine solve a set of 68 coupled equations

  7. ionizing background 10x 4x 2x 1x ionizing radiation: local universe – extragalactic background z = 0 (Haardt & Madau 1996, 2001)

  8. carbon ionization states: example 1x 2x 4x 10x non-equilibrium collisional state- black non-equilibrium photo state - color

  9. carbon ionization states: example 1x 2x 4x 10x non-equilibrium collisional state- black non-equilibrium photo state - color

  10. 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

  11. ionization state ratios • Vilchez & Iglesias-Paramo 2003

  12. ionization state ratios temperature

  13. 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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