That doesn't make sense. Wouldn't they be an arm of the Justice Department. I am against the court having it's own army to enforce it's rulings. That is for the executive power to carry out.
Actually, you are correct.. US Marshall's are appointed by the President and/or the US Attorney General's Office. They are there to work for the Judicial Branch.. There are only 95 US Marshall's in the United States.
http://www.usmarshals.gov/duties/index.html
For over 200 years, U.S. Marshals and their Deputies have served as the instruments of civil authority by all three branches of the U.S. government