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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 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 • 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
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
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)
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
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
ionizing background 10x 4x 2x 1x ionizing radiation: local universe – extragalactic background z = 0 (Haardt & Madau 1996, 2001)
carbon ionization states: example 1x 2x 4x 10x non-equilibrium collisional state- black non-equilibrium photo state - color
carbon ionization states: example 1x 2x 4x 10x non-equilibrium collisional state- black non-equilibrium photo state - color
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
ionization state ratios • Vilchez & Iglesias-Paramo 2003
ionization state ratios temperature
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!!!