The host galaxies and progenitors of Fast Radio Bursts localized with
  the Australian Square Kilometre Array Pathfinder
  The Australian SKA Pathfinder (ASKAP) telescope has started to localize Fast
Radio Bursts (FRBs) to arcsecond accuracy from the detection of a single pulse,
allowing their host galaxies to be reliably identified. We discuss the global
properties of the host galaxies of the first four FRBs localized by ASKAP,
which lie in the redshift range $0.11<z<0.48$. All four are massive galaxies
(log( $M_{*}/ M_{\odot}$) $\sim 9.4 -10.4$) with modest star-formation rates of
up to $2M_{\odot}$yr$^{-1}$ -- very different to the host galaxy of the first
repeating FRB 121102, which is a dwarf galaxy with a high specific
star-formation rate. The FRBs localized by ASKAP typically lie in the outskirts
of their host galaxies, which appears to rule out FRB progenitor models that
invoke active galactic nuclei (AGN) or free-floating cosmic strings. The
stellar population seen in these host galaxies also disfavors models in which
all FRBs arise from young magnetars produced by superluminous supernovae
(SLSNe), as proposed for the progenitor of FRB 121102. A range of other
progenitor models (including compact-object mergers and magnetars arising from
normal core-collapse supernovae) remain plausible.
