Cosmological Inference from Host-Selected Type Ia Supernova Samples
  We compare two Type Ia supernova (SN Ia) samples that are drawn from a
spectroscopically confirmed SN Ia sample: a host-selected sample in which SNe
Ia are restricted to those that have a spectroscopic redshift from the host;
and a broader, more traditional sample in which the redshift could come from
either the SN or the host. The host-selected sample is representative of SN
samples that will use the redshift of the host to infer the SN redshift, long
after the SN has faded from view. We find that SNe Ia that are selected on the
availability of a redshift from the host differ from SNe Ia that are from the
broader sample. The former tend to be redder, have narrower light curves, live
in more massive hosts, and tend to be at lower redshifts. We find that
constraints on the equation of state of dark energy, $w$, and the matter
density, $\Omega_M$, remain consistent between these two types of samples. Our
results are important for ongoing and future supernova surveys, which unlike
previous supernova surveys, will have limited real-time follow-up to
spectroscopically classify the SNe they discover. Most of the redshifts in
these surveys will come from the hosts.
