1. Mixing of metals in blue LSB galaxies (or How one can measure their ages) Yuri Shchekinov (Southern Federal U) Eduard Vorobyov (St. Marry U, S Fed U) Domink Bomans (AI RUB) Ralf-Jurgen Dettmar (AI RUB) Dmitry Bizyaev (New Mexico State U, Sternberg AI) Nearby Dwarf Galaxies, SAO Nizhny Arkhyz, 14-19 September 2009

2. LSBs vs hierarchical structure formation colors gas mass metallicities LSBs may have formed recently !

3. Padoan etal 1997, Jimenez etal 1998: U-B, B-V, B-R, V-I photometry  t≥7-9 Gyr Aging Schombert etal 2001: HI content, V-I photometry  LSB dwarfs t≤5 Gyr Haberzettl etal 2005: Spectral energy distribution  t=2-5 Gyr Zackrisson etal 2005: optical/NIR photometry + H-alpha EW  t=1-2 Gyr (though 10-14 Gyr equally well reproduce the data) Vorobyov, YuS, Bomans, Dettmar & Bizyaev 2009: aging through chemical inhomogeneity

4. 2D hydrodynamic simulations: ∫.. dz + chemistry (instantaneous recycling) + photometry + sporadic SF

5. Mixing in the MW Shock frequency Draine & Salpeter 1979

6. Mixing in the MW Numerical examples Avillez & MacLow 2002 t=0 t=50 Myrt=126.6 Myr

7. Mixing in LSBs Shock frequency with a 0.1 SFR Boissier etal 2008 t=126.6 Myr in the MWt=1.266 Gyr in LSB 

8. SF in LSBs = 0.1 SF in MW SNR filling factor assume linear proportionality

9. no mixing ! unless differential rotation & spiral waves help Mixing in LSBs

10. Dynamical model of a LSB

11. V(R) de Blok 05

12. Dynamical model of a LSB Equations: 2D hydro+instantaneous recycling

13. Dynamical model of a LSB SF scenario: sporadic SF Schmidt law SF sites randomly distributed through the disk if T < T cr = 10 K 4 Δ t = 20 Myr SF

14. Radiative gas T 10 2 4 cooling rate (erg cm3/s)

15. Radiative gas T 10 2 4 cooling rate (erg cm3/s)

16. Dynamical model of a LSB SF scenario: sporadic SF

17. H-alpha emission: sporadic SF ESO-LV 0280140 model Auld et al 2006

18. H-alpha emission: sporadic SF model ESO-LV 1040220 Auld et al 2006

19. H-alpha emission: sporadic SF ESO-LV 1450250 model Auld et al 2006

20. Dynamical model of a LSB Metal mixing

21. Dynamical model of a LSB Metal mixing

22. Dynamical model of a LSB Metal mixing

23. Radial distribution of oxygen no grad in Z  no SF threshold

24. Radial distribution of oxygen ! Observations by de Block & van der Hulst 1998

25. Oxygen abundance

26. H-alpha EW

27. Oxygen & H-alpha EW S K

28. Conclusions Patchy distribution of metals (1-2 kpc) remains distinguishable (0.5-1.0 dex) on 1-2 Gyr The abundance fluctuation spectrum is age-dependent, though hardly resolved [O/H] vs H α EW seems good for constraining the age provided a preliminary information of the IMF is available Combined [O/H] and Hα EW data constrain LSB ages between 7 and 13 Gyr

29. Спасибо !