Unknown accounts in Active Directory properties

[EME_IT]

I have some unknown accounts in my Active Directory. When I right click and go to properties in the root of my domain, I see some accounts that show up as "Unknown Accounts". My question is: Can I remove these accounts? What happens if I remove these accounts? Below is a screenshot to better visualize my question.

[#2]

@EME_IT the most common cause is that these accounts were once valid user accounts but have since been deleted. When a user account is removed, its sid remains in the system, my understanding is they are safe to remove..

[#3]

@Rupo_Zhang Exactly. I removed them all yesterday. As these were AD properties, I decided to ask for a second opinion here. Thanks!