Hello, lompaket. Thank you for that great question! The verb in this sentence is the past tense of the verb head. In this context, it means "to lead." The author is talking about the "head of the household." The person who heads the household can be considered the leader, or boss of the family. Usually, as this refers to a person with power, it is the person who works or earns the most. The sentence you submitted refers to the families whose head (of the family) is an immigrant. Traditionally, in America, for example, the head of the household was the father. In modern society, that has changed. As an example, in a single-parent household (or family) where there is only a mother, she would head the household. Another context for using the word head with the meaning 'to lead' would be in a horse race, the one at the front is at the head.