The history of metal enrichment of NGC3115 galaxy : monolitic vs merger formation

The history of metal enrichment of NGC3115 galaxy : monolitic  vs  merger formation. 

Chemical evolution of  the massive lenticular galaxy NGC3115 is considered. In the framework of monolithic and  hierarchical merger scenaries, observed stellar metallicity distributions for the outer and intermediate halo regions of a given galaxy were simulated. It is shown that the "excess" of metal-poor stars  in the  metallicity distribution of the outer halo  of NGC 3115 can be reproduced quite well in the framework of merger scenario. At the same time, the observational  stellar metallicity distribution  for the intermediate halo does not show such an "excess", therefore, this can be reproduced in a monolithic model with accretion of unenriched gas. The obtained results allows to assume that a formation of the outer halo  of galaxy NGC3115 could occur by accretion of individual non-massive fragments and such fragments must be at least 6.