NEW EVOLUTIONARY MODELS OF HII GALAXIES

1. Mariluz Martín Manjón* Mercedes Mollá** Ángeles I. Díaz* *Universidad Autónoma de Madrid ** CIEMAT ESTALLIDOS V Granada, 2007 NEW EVOLUTIONARY MODELS OF HII GALAXIES

2. INTRODUCTION • Are HII galaxies young systems? How the star formation takes place in HII galaxies? We have used three tools: 1st. Chemical evolution code: (Ferrini et al.1992 , Mollá et al. 1996, Mollá & Díaz 2005) t=0-13.2 Gyr, Δt=0.5 Myr age, metallicity, abundances 2nd. Evolutionary synthesis code: (García –Vargas et al. 1995, Mollá & García-Vargas, 2000) S.E.D ionizing continuum 3rd. Photoionization code: (CLOUDY, Ferland et al. 1991) Emission lines

3. ATTENUATED BURST MODELS • From t=0 to t=13.2 Gyr , Δt= 0.5 Myr • Mtot= 100·106M • R= 500 pc (Telles et al. 1997) 10 attenuated bursts every 1.3 Gyr. Different initial efficiencies and attenuations have been taken. Attenuation modes: n=number of the burst nn= attenuation factor Type 0 Type 1 Basic model More attenuated than type 0 Less attenuated than type 0 Increasing efficiency

4. Star formation rates Type 1 nn=0.5 Type 0 10% 3% 33% 10% 33% 64% Type 1 nn=1.2 Type 1 nn=0.8 3% 3% 10% 10% 33% 33%

5. HII galaxies: 7.5 < 12+log(O/H) < 8.5 (Hoyos & Díaz 2005, Terlevich et al. 1991) Oxygen abundance Type 1 nn=0.5 Type 0 64% 33% 10% Type 1 nn=1.2 Type 1 nn=0.8

6. Ionized gas: diagnostic diagrams I Type 0 Є=10% Є=33% Data compilation: Hoyos & Díaz 2006

7. Diagnostic diagrams II Є=10% Є=33% Type 1 nn=0.5 high attenuation

8. Diagnostic Diagrams III Type 1 nn=0.8, low attenuation Є=3% Є=10% Є=33%

9. Diagnostic Diagrams IV Type 1 nn=1.2, increasing s.f.r. Є=3%

10. EW(Hβ) vs. colour Type 0 33% • Evolution of colour is reproduced with the contribution of the underlying population,not with a SSP. Observational data: Hoyos & Díaz 2006 Salzer et al. 95 Terlevich et al. 91

11. EW(Hβ) vs. colour • With a high attenuation we can cover the whole range of data. The contribution of the continuum is higher than the blue colour of the burst . • nn=0.5, є =33% nn=0.8 Є= 10% nn=1.2 Є=3%

12. SUMMARY & CONCLUSIONS • We have made models combining a chemical evolution code, an evolutionary synthesis code and a photoionization code, from t=0 to t=13.2 Gyr, Mtot=108M⊙ and R= 500pc, with 10 starburts every 1.3 Gyr . • Different efficiencies and attenuations have been chosen to reproduce the HII galaxies, from Hoyos & Díaz (2006) catalogue. • -The values in every model are between 3% and 33% of initial efficiency, depending on the attenuation, according to oxygen abundance. • - Emission lines can be reproduced with these models, being the best fit model, in average, a model with 33% of initial efficiency and high attenuation • - Studying the equivalent width versus colour diagrams, we can see that it is necessary to include the contribution of the underlying populations to reproduce the tendency of the observations, that it is not reproduced with SSPs. • To reproduce the whole range of the observations in colour, not only the tendency , the contribution of the underlying population must be higher than the blue colour of the current burst.