Marta Gavilán Bouzas Mercedes Mollá Lorente Estallidos IV, Granada

What are we looking for? We are looking for some signs to know if dwarf galaxies lose some of their gas or not. How do we looking for it? Our aim is to have a large amount of model results (in an autoconsistent way) to obtain the maximum number of clues. We analized: gas content, metallicity and photometry and compare them with observations.

A short review Galactic Chemical Evolution Model Grid of models

Galactic Chemical Evolution Model The free parameters are: the collapse time: Tcol the efficiency in forming molecular clouds:   the efficiency in transform the clouds into stars:  h The SFR is a RESULT not an INPUT There are no STAR BURSTS: the star forming process is continuous, but not constant

Grid of Models Mass interval: Six values From M  to M  Collapse time: Four values From 8 Gyr to 60 Gyr Star Formation Parameters: Four values S, M, L, XL TOTAL GRID: 96 Models

SFR HISTORIES Lower Tcol and Higher   and  h    Higher Tcol and Lower   and  h    Efficiency=0.88 Efficiency=0.40 Efficiency=0.17

Effective Yield p = The gas fraction estimation

Oxygen Effective Yield f Mgas/fYo Mgas*fYo

Oxygen Abundance Models Garnett 02 DwGx Van Zee 06 Garnett 02 S Ln(1/  ) Tot

IIZw70 Kherig and col 2007  = 0.30  = 0.24  = 0.21  = 0.40

Other observations M(HI) Observations Kong M  Cox et al M  Larsen et al M  Mas-Hesse & Kunth M  Our Model M  < M(HI) < M  M B Observations Kong Gil de Paz et al Cairós et al Cox et al Larsen et al Our Model < M B <-16.7

CONCLUSIONS Our models present an effective yield without gas outflow according with most observations. The models with high efficiency give too much high abundances. It is possible that they do not match with any observations. In the case of IIZw70 we reproduce the SFR and the (O/H) value with no star burst. …but the gas content needs additional explanation.