  Tidal interactions between galaxies can trigger star formation, which
contributes to the global star formation rate density of the universe and could
be a factor in the transformation of blue, star-forming galaxies to red,
quiescent galaxies over cosmic time. We investigate tidally-triggered star
formation in isolated close galaxy pairs drawn from the Prism Multi-Object
Survey (PRIMUS), a low-dispersion prism redshift survey that has measured
~120,000 robust galaxy redshifts over 9.1 deg^2 out to z ~ 1. We select a
sample of galaxies in isolated galaxy pairs at redshifts 0.25 < z < 0.75, with
no other objects within a projected separation of 300 h^-1 kpc and dz/(1+z) =
0.01, and compare them to a control sample of isolated galaxies to test for
systematic differences in their rest-frame FUV-r and NUV-r colors as a proxy
for relative specific SFR. We find that galaxies in r_p < 50 h^-1 kpc pairs
have bluer dust-corrected UV-r colors on average than the control galaxies by
-0.134 +/- 0.045 magnitudes in FUV-r and -0.075 +/- 0.038 magnitudes in NUV-r,
corresponding to a ~15-20% increase in SSFR. This indicates an enhancement in
SSFR due to tidal interactions. We also find that this relative enhancement is
greater for a subset of r_p < 30 h^-1 kpc pair galaxies, for which the average
colors offsets are -0.193 +/- 0.065 magnitudes in FUV-r and -0.159 +/- 0.048
magnitudes in NUV-r, corresponding to a ~25-30% increase in SSFR. We test for
evolution in the enhancement of tidally-triggered star formation with redshift
across our sample redshift range and find marginal evidence for a decrease in
SSFR enhancement from 0.25 < z < 0.5 to 0.5 < z < 0.75. This indicates that a
change in enhanced star formation triggered by tidal interactions in low
density environments is not a contributor to the decline in the global star
formation rate density across this redshift range.

Cosmology and Nongalactic Astrophysics