HUGE pg_sorttemp files, can I delete?

In my /var/postgres/base/database directory I've got a bunch of REALLY big
files that are from several months ago:

-rw-------    1 postgres postgres 191684608 Oct 30 23:35 pg_sorttemp10964.0
-rw-------    1 postgres postgres 192126976 Oct 30 23:44 pg_sorttemp11353.0
-rw-------    1 postgres postgres 192126976 Oct 30 23:44 pg_sorttemp11369.0
-rw-------    1 postgres postgres   983040 Oct 23 17:37 pg_sorttemp22475.0
-rw-------    1 postgres postgres 26787840 Oct 21 14:00 pg_sorttemp2372.0
-rw-------    1 postgres postgres 130465792 Nov  9 13:42 pg_sorttemp30831.0
-rw-------    1 postgres postgres 232701952 Oct 30 20:41 pg_sorttemp5564.0
-rw-------    1 postgres postgres 232701952 Oct 30 20:41 pg_sorttemp5576.0
-rw-------    1 postgres postgres 232701952 Oct 30 20:41 pg_sorttemp5588.0
-rw-------    1 postgres postgres 232792064 Oct 30 20:41 pg_sorttemp5749.0
-rw-------    1 postgres postgres 190275584 Oct 30 20:41 pg_sorttemp6480.0
-rw-------    1 postgres postgres 190275584 Oct 30 20:41 pg_sorttemp6494.0

There are some there that are from today - but from Oct 30? Can I delete
these files? What are causing these? Can I set a limit or something? My
database is 3.6 gigs, that is HUGE. I think it is largely because of these
files.

Thanks!

Micah

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Micah Anderson
Collective Technologies
www.colltech.com

"To be and not to do is not to be at all"