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

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 BCDs photoizined gas in DM minihalos Gnat & Sternberg 2004 neutral cores: OI, NI, CII, SiII ionized shielding envelopes: CIV, NV, OVI background

collisional ionization equilibrium (CIE) Cox & Tucker 1969, Raymond et al. 1976, Shull & van Steenberg 1982, Gaetz & Salpeter 1983, Sutherland & Dopita 1993, Benjamin et al non-equlibrium (time-dependent) radiative cooling Kafatos 1976, Shapiro & Moore 1976, Edgar & Chevalier 1986, Schmutzler & Tscharnuter 1993, Sutherland & Dopita 1993, Gnat & Sternberg 2007 calculations of the cooling rates of astrophysical plasma strong difference between equlibrium and non-equilibrium cooling rates & ionization states Gnat & Sternberg 2007

presence of UV radiationequlibrium strong suppression of the cooling rates of H+He plasma Efstathiou (1992) enriched gas Wiersma et al. (2008) - EQ calculations of the cooling rates of astrophysical plasma equlibrium ~ non-equilibrium a) low metallicity b) high ionizing flux c) low density or b) + c) high ionization parameter non-equilibrium collisional rates (dash) equilibrium photo rates (dot) non-equilibrium photo rates (solid) EV, in preparation

equlibrium or non-equilibrium: example DWs: number densities – cm -3 & low flux transition from EQ to NEQ non-equilibrium collisional state – black solid non-equilibrium photo state - color NEQ collisional n = cm -3 n = cm -3 n = cm -3 EQ NEQ EV et al., in preparation

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 atomic data and model description

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

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

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

ionization state ratios n = cm -3 - dot n = cm -3 - solid n = cm -3 - dash decrease density NEQ collisional [Z] = 0 [Z] = 0 [Z] = -1 [Z] = -3 Neq Eq non-equilibrium collisional state - black non-equilibrium photo state - color ionizing radiation: extragalactic background z = 0 (Haardt & Madau 1996, 2001)

ionization state ratios Vilchez & Iglesias-Paramo 2003

ionization state ratios temperature

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. conclusion & future thank you!!!

conclusion & future

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

log T metallicity flux redshift power-law, a = 1 extra-galactic back-d r = non-equilibrium rate / equilibrium rate ratio of cooling rates gas density