Astron. Astrophys. 357, 471-483 (2000)

5. Summary and discussion

With our work we found NGC 1960 to be a young open star cluster with an age of 16 Myr. It is located at a distance of 1300 pc from the Sun. These results confirm the findings of Barkhatova et al. (1985) obtained with photographic photometry.

We derived proper motions of 404 stars in the region of the cluster down to . 178 of those can be considered members of NGC 1960. Despite the problems with our proper motion determination (see Sect. 3.1), we are able to state that our results do not support the values given as the absolute proper motion of NGC 1960 by Glushkova et al. (1997) on the base of the "Four Million Star Catalog" (Gulyaev & Nesterov 1992): They found which is in agreement with our study, but which differs from our result by more than .

Our study of the IMF of NGC 1960 led to a power law with a slope of . This value is very high (i.e. the IMF is shallow) compared to other studies, however, it still matches the interval for suggested by Scalo (1998) for intermediate mass stars ().

Although we should stress that we cannot say anything about the shape of the IMF in the very low mass range (), we do not see any evidence for a flattening of the IMF of NGC 1960 below .

NGC 2194 - with an age of 550 Myr - belongs to the intermediate age galactic open star clusters. Our findings from the photometric study are in good agreement with the photographic RGU photometry published by del Rio (1980).

As the cluster is located at a distance of almost 3 kpc we could only cover its mass spectrum down to . Nevertheless, we were able to determine the IMF on the base of 623 main sequence stars which led to a slope of , almost Salpeter's (1955) value, but still close to the shallow end of the interval given by Scalo (1998).

In our previous paper (Sanner et al. 1999), we studied the open star cluster NGC 581 (M 103) for which we found the same age of Myr as for NGC 1960, but a much steeper IMF slope of . We therefore can state that our method of IMF determination does not systematically lead to steep or shallow mass functions.

With our yet very small sample, it is not possible to find evidence for the dependence of the IMF of open star clusters on any parameter of the cluster. Therefore, we will have to investigate further clusters and also compare our results with other studies.

© European Southern Observatory (ESO) 2000

Online publication: June 5, 2000
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