samba - Aug 2005 - Unix server joining NT4 Domain--User question

Hi,

I have recently installed samba 3.0.14a on an AIX 5.2.0.6 server.  I have 
joined the AIX server to a NT4 domain called ESC.  When I do a wbinfo -u  I 
get the users of the domain.  I then setup a share "psoft" that I want
to be
"read only" to everybody but 5 users.  Those 5 users I've added to
the
"write list" of that share.  I also setup the "force user"
and "force group"
of the share to be psoft and psoft respectively.  These 5 users do not know 
how to login to the psoft unix user due other things that unix user does.

This share is basically a read only share of the application files which are 
on the server.  Only 5 people apply patches to the software.  The read only 
is working.  The users can be authenticated and work _only_ if I add a 
matching unix user in /etc/passwd.  Due to recent audit problems, I do not 
want to make unix users at all (Besides, I'm force user/group'ing
anyways).

Is it not possible to have an NT4 PDC authenticate a user and that user 
_not_ exist as a unix user?