Could Syncing the User profile Service with AD, remove users from the User Profile Service if users are no longer inside the AD

Question

I am working on a sharepoint farm 2013 on-premises, and i have the following settings for the user profile service:-

1. currently i have created a user profile service, but there is not any sync with AD.
2. so currently when a new user access any site collection, a new user profile will be created automatically for the user.
3. now some users who have their user profiles created inside the user profile service, have left the company. so there are no accounts for them inside the AD.

now i am not sure what will happen if we chose to sync the user profile service with AD? so what will happen to the user profiles inside the user profile service which no longer exists inside the AD?? will they get removed from the user profile service? if the answer is Yes (they will be removed) then what will happen to the items and pages which have the createdby and modifiedby equal to the users who left the company ? will it be set to system account for example?

Answer 1

What should happen is the profiles that are not matched to AD accounts should be marked as "Missing From Import". A timer job will run eventually removing the profiles. The content they created in team sites will remain as will their name for content associated as Created By or Modified By. This is by design. The record associated with their content is actually stored in a hidden list in each site collection. So, even if their profile is removed either automatically or manually the content will still be linked to their User Info List entry in the site collection.