New Sydney is an independent mining colony located in the Sappora system. Due to the planet's independence from Starfleet and the Federation, the planet is influenced by the Orion Syndicate, and is the home of many nefarious races, such as the Ferengi and the Nausicaans.
Due to the Cardassian annexation of Bajor, the Bajoran Arla family relocated from B'hal Ta to New Sydney. Arla Rees was born on the planet. (DS9 - Millennium novels: The Fall of Terok Nor, The War of the Prophets)