Why is a hash match operator in this very basic query
The first query is using a parallel plan, meaning the "work" was split into multiple tasks carried out by multiple threads. The cumulative CPU time was therefore higher than for the serial plan used for your second query.

As to why the distinct causes the hash match operator to appear in the plan; an aggregate or sort operation is required to determine the DISTINCT result. @SQL_Kiwi might pop up with a more indepth explanation shortly but the hash match operator is apparently favoured for larger result sets.


  The optimizer tends to prefer the Hash Match Aggregate on larger
  rowsets, with fewer groups, where there is no reason to produce a
  sorted output, and where the incoming rows are not sorted on the
  DISTINCT expression(s).  Larger inputs favour hash matching because
  the algorithm generally scales well (although it does require a memory
  grant) and can make good use of parallelism.  Fewer groups are better
  for hashing because it means fewer entries in the hash table, and the
  memory needed to store unique values is proportional to the number of
  groups (and the size of the group).  Hash matching does not require or
  preserve the order of the incoming row stream. [Source]