Deltek Inc.,  a leading market research and business management company, announced today that it has been bought by private equity firm Thoma Bravo for roughly $1.1 billion. Deltek, which is now publicly traded, will be privately held under the deal. Deltek’s stockholders will receive $13 in cash for each share when the transaction closes, the company said in a news release. Deltek’s board of directors and its  largest shareholder, New Mountain Capital, approved the acquisition. Deltek, which earned $341 million last year and has more than 1,600 employees, provides services to 98 of the top 100 federal contractors.  The company’s revenues increased more than 20 percent between 2010…