Most tight players don't call raises w/ AJ (suited or unsuited). I personally think he is raising w/ AK of hearts here. He could also have a set of 2s. A lot of tight players won't call raises w/ small pocket pairs but a lot do based on implied odds. He could also have JJ or QQ but those are unlikely since all 4 of either would be out. He could also have AQ. Therefore, his most likely holdings are AhKh, AQ, or 22, with an outside chance of QQ or JJ.