In my opinion, you still own the same property. You have only subdivided your property into two separate properties. As far as your tax return in concerned, I would report two properties on my Schedule E instead of just one as you had done previously.
Keep the same depreciation schedule you had before, just allocate half of your cost basis (and remaining depreciation basis) in the duplex to each condo. Continue depreciating over the remainder of the depreciation schedule.
Subdividing your property and converting to condo comes at a price. You incurrred survey costs, recording fees, legal fees to draft condo association bylaws, separate metering installation and hookup costs for power, water/sewer, gas, etc.
Consult your CPA for specific details on how to capitalize these costs and your tax reporting.