  The architectures of debris disks encode the history of planet formation in
these systems. Studies of debris disks via their spectral energy distributions
(SEDs) have found infrared excesses arising from cold dust, warm dust, or a
combination of the two. The cold outer belts of many systems have been imaged,
facilitating their study in great detail. Far less is known about the warm
components, including the origin of the dust. The regularity of the disk
temperatures indicates an underlying structure that may be linked to the water
snow line. If the dust is generated from collisions in an exo-asteroid belt,
the dust will likely trace the location of the water snow line in the
primordial protoplanetary disk where planetesimal growth was enhanced. If
instead the warm dust arises from the inward transport from a reservoir of icy
material farther out in the system, the dust location is expected to be set by
the current snow line. We analyze the SEDs of a large sample of debris disks
with warm components. We find that warm components in single-component systems
(those without detectable cold components) follow the primordial snow line
rather than the current snow line, so they likely arise from exo-asteroid
belts. While the locations of many warm components in two-component systems are
also consistent with the primordial snow line, there is more diversity among
these systems, suggesting additional effects play a role.
