Facebook has now setup ad targeting option for any audience you want to target. If you looking to target immigrant audience you can reach to that audience using keywords like interests and behaviors etc also its amazing most people use mobile and you can target immigrants who use mobiles tool. As your preference.

Facebook Immigrant audience add,

small Audience
Mobile
25.2M MMAUs
Highly engaged
Stay awasy from home town
stay away from family
Percentage who return to Facebook daily
Over index on all key engagement metrics (comments, messages, likes)

How to Identify Immigrant audience

The Immigrant audience cluster is not designed to identify people who are straight Immigrant. It is based on actual users who shared their personal information through facebook about info and profile base information

How Fb Segment audience?

How to access: Audience > More Demographics > Ethnic Affinity >…..

Language-based targeting within US Hispanic Affinity 1
Bilingual
English
Other Languages select what you targeting.

How to access: Audience > More Demographics > Ethnic Affinity > you target immigrant audience etc
Use these segments with other Facebook targeting solutions to further refine your audience