Signals of merging supermassive primordial black holes in pulsar timing arrays

Understand

In this work we evaluate whether the gravitational wave background recently observed by a number of different pulsar timing arrays could be due to merging primordial supermassive black hole binaries.

• We find that for homogeneously distributed primordial black holes this possibility is inconsistent with strong cosmological and astrophysical constraints on their total abundance.
• If the distribution exhibits some clustering, however, the merger rate will, in general, be enhanced, opening the window for a consistent interpretation of the pulsar timing array data in terms of merging primordial black holes, if $\mu$-distortion constraints associated with the formation mechanism can be evaded.