The pearl river delta is an extended metropolitan region of nearly 50 million people, encouraged by the chinese government as an engine of economic growth and built around the already established economic success of

Guandong.

Explanation:

Guandong province is the wealthiest region of China. It´s a manufacturing and export center, the largest economic hub. More than 26% of Chinese exports originate in this area.  It has become a symbol of succesful economic reforms that have made China the second world economy. Guandong and the Pearl River Delta include such modern cities as Shenzhen, Guangzhou, Zhuhai, Foshan, Dongguan, Jingmen, and the two special administrative regions of Hong Kong and Macau.

because the center-south is called the heart of the country

i think the reason that they immagrated was to find freedom of religion