The Z-L relationship: Some clues for galaxy evolution

Gas-rich dwarf galaxies are probably the best objects to study signatures of a process of self-regulation between the disk and the halo. A qualitative picture about the process of self-regulation follows: in galactic gas halos with a short cooling time, halo clouds will infall ballistically if they are not destroyed by ram pressure due to the interaction with the wind. This fresh gas will activate star formation and the wind until ram pressure is able to reduce the accretion rate, resulting in a self-regulation mechanism. If this process is at work then the b-parameter defined as b ≡ A/(A - W), with A the mass accretion rate and W the rate of mass lost in the wind, should be very constant with time. Here our objective is to check whether simple chemical models that include infall of cooling gas and outow of hot gas with constant b can explain the variations in metallicity of dwarf galaxies. In particular, we aim to discern whether the b-parameter could be similar for different types of dwarf galaxies, or i.e. on the contrary, each type requires a different A/W-ratio. In order to study the self-regulation conditions, the relationship between the metallicity (Z) and the luminosity (L) is used.