What is the antecedent of those?

Any noun or pronoun can be an antecedent for the demonstrative pronoun 'those'. When the demonstrative pronouns (this, that, these, those) are used, there is often no antecedent used because the pronoun is taking the place of the noun or pronoun. Examples:

All of the flowers are beautiful, just look at those. (the noun 'flowers' can be considered the antecedent but the pronoun 'those' may be referring to only some of the whole group)

They all look so good. I'll have one of those. (again, the indefinite pronoun 'all' can be considered the antecedent but the pronoun 'those' is is referring to a specific type of the whole group)

They're mom's favorite so I'll buy those for her. (in this case, the pronoun 'they' is the antecedent because 'those' is referring directly back to the pronoun)