What is the "cores" directory at top level and their core.99999 files?

At the top level of my Disk is a hidden directory called "cores".

Within that directory are 105 files called "core.99999".

The 99999 is a system assigned number?

Each file is 380MB or very close, ie some are 381, some are 385.

Each file of a particular size appears to arise in blocks of 8, 16, or 64

My MacBook (early 2008) 4GB/750GB has been running slowly particularly when Safari builds up more than 3 Gb of Virtual Memory requirement.

I found these files after a SuperDuper! backup showed about 40Gb less on the mirrored disk than on the inbuild system disk. I went searching with GrandPerspective and they appeared, beautifully arranged at top level of the disk, with the hidden cores directory at the same level as the System, Applications, Library and Users directories.

I never saw these before in 10.6 Snow Leopard.

Can I delete them manually, or via a procedure? They take up a lot of space.

I am concerned they may be reason my MacBook pages VM very slowly as teh VM requirements of the programs I am running increases beyond 5 GB