ARE LOW SURFACE BRIGHTNESS DISKS YOUNG

We reconsider the problem of the age of the stellar disks of late-type low surface brightness galaxies (LSBs) by making use of a new IMF rec ently derived from numerical fluid dynamics simulations (Padoan, Nordl und, & Jones 1997), and a new synthetic stellar population code, based on Jimenez & MacDonald (1997) evolutionary tracks and Kurucz atmosphe ric models (Kurucz 1992). We find that the disks of LSBs are not neces sarily formed very recently. Their colors seem to indicate that the di sks of LSBs started to form stars at least 7 Gyr ago, and more likely about 9 Gyr ago, and therefore contrary to what has been claimed in th e literature disks of LSBs are not young.