var log vmware Core file

Hi,

Trying to do some cleanup on our ESX3 box.  There was a lot of old log files piling up so we removed the majority of them.  Can someone explain the larger 'core' file/s in /var/log/vmware/ ?  There were alot more like core.1234, core.8793 etc and we're not realy sure what they are from except that they were from 2007 unlike the one below;

# ls -lh /var/log/vmware

total 206M

-rw-------    1 root     root         163M Apr 13  2009 core