General Discussion on Population Synthesis Modelling

Abstract

Van den Heuvel: I am sure you will agree with me that from the talks we heard today we are all very impressed by the progress made in our understanding of the role of binaries in the evolution of stellar populations. The last talk, by Onno Pols as well as the talks this morning by Simon Portegies Zwart and by Fred Rasio clearly showed that in studying the evolution of dense star clusters real understanding can only be achieved if the dynamics is included in combination with the evolution of the individual stars and binaries. The talk of Pols showed that even in an open cluster such as M67 the dynamical effects are not small perturbations, and that the presence of a variety of very peculiar objects in that cluster, such the Super Blue Stragglers, could never be understood if dynamics was not included. This mornings talk by Portegies Zwart on the Hyades showed the same. We have seen that, in order to include the evolution of binaries in Population Synthesis, many input distributions are needed and many input-assumptions have to be made. A systematic list of these was given in several of the talks, particularly those of Kalogera, Fryer and Van Bever. Fryer gave on one transparency a very nice overview of all ingredients that go into these simulations and he was so kind to lend it to me to show to you again: one sees that the number of input assumptions that have to be made is impressive.(Van den Heuvel shows the transparancy). There are, of course, a number of input assumptions on which we all more or less agree, but there are also assumptions that have great uncertainties and which we should discuss. Furthermore, there are still many open questions on which we would like to find answers. In order to somewhat structure the discussion, I first of all would like to discuss with you the input assumptions for Population Synthesis and after that I would like to reserve the second half of our discussion to the open questions.