Simon Property Group Inc. has made a $22.4 billion unsolicited bid for Macerich Co., a deal that would combine two of the largest U.S. shopping-mall owners,Bloomberg reported. Macerich is the owner of Southridge Mall in Des Moines. The California-based company has its corporate roots in Central Iowa. Simon, the No. 1 mall owner, went public with its bid today after being rebuffed by Macerich, the country’s No. 3 mall owner, during private discussions late last year and in February. The offer, in cash, stock and assumed debt, may be the opening salvo in a protracted takeover battle for the real estate investment trust, analysts said. Macerich confirmed the bid in a news release and said its board would review the offer with its financial and legal advisers. “This is their first shot across the bow,” David Auerbach, an institutional REIT trader at Esposito Securities LLC in Dallas, told Bloomberg about Simon’s offer. “I don’t think this is the best bid Simon could put in front of them.” Southridge Mall was built by another large mall owner with Des Moines roots, General Growth Properties Inc. The mall was bought in 1998 by Macerich and Simon Property Group, with Macerich taking over sole ownership in January 2012.