The resolved stellar populations in the LEGUS galaxies
  The Legacy ExtraGalactic UV Survey (LEGUS) is a multiwavelength Cycle 21
Treasury program on the Hubble Space Telescope. It studied 50 nearby
star-forming galaxies in five bands from the near UV to the I-band, combining
new Wide Field Camera 3 observations with archival Advanced Camera for Surveys
data. LEGUS was designed to investigate how star formation occurs and develops
on both small and large scales, and how it relates to the galactic
environments. In this paper we present the photometric catalogs for all the
apparently single stars identified in the 50 LEGUS galaxies. Photometric
catalogs and mosaicked images for all filters are available for download.
  We present optical and near UV color-magnitude diagrams for all the galaxies.
For each galaxy we derived the distance from the tip of the red giant branch.
We then used the NUV color-magnitude diagrams to identify stars more massive
than 14 Mo, and compared their number with the number of massive stars expected
from the GALEX FUV luminosity. Our analysis shows that the fraction of massive
stars forming in star clusters and stellar associations is about constant with
the star formation rate. This lack of a relation suggests that the time scale
for evaporation of unbound structures is comparable or longer than 10 Myr. At
low star formation rates this translates to an excess of mass in clustered
environments as compared to model predictions of cluster evolution, suggesting
that a significant fraction of stars form in unbound systems.
