NEW YORK–Citing a rapid integration with the IntercontinentalExchange Group, Duncan Niederauer will step down as CEO of the New York Stock Exchange immediately.Thomas Farley, NYSE's chief operating officer, will succeed Niederauer, taking the title of president of the NYSE Group.Niederauer, 54, served as CEO of NYSE Euronext, the company that owns the New York Stock Exchange, from 2007 through late 2013. He will continue as preside??nt of ICE through Aug. 2, ICE said. Niederauer had been expected to stay until the end of the year.ICE, the futures exchange based in Atlanta, closed on its acquisition of the NYSE in November for about US$8 billion in cash and stock. (AP)