A simple question

Hello,
I wonder if postgres autocreates an index on foreign or primary key fields.

For example:

create table t1 (
  f1 integer,
  f2 varchar,
  primary key (f1));

create table t2 (
  f1 integer,
  f2 integer,
  primary key (f1),
  foreign key (f2) references t1(f1)
);

In this sample, "t1" has a primary key, and "t2" both (primary and foreign
keys).
Does postgres create each indexes for the primary key of "t1" and "t2" ?

and indexes for "f2" field in "t2" ?

I expleain, there are several DBMS where autocreates these indexes for you,
and others that shows you an alert, for example, if you don't create an unique
index for the primary key.

Thanks.