Bright Lyman $\rm \alpha$ emitters among Spitzer SMUVS galaxies in the
  MUSE/COSMOS field
  We search for bright Ly$\rm \alpha$ emitters among Spitzer SMUVS galaxies at
z > 2.9 with homogeneous MUSE data. Although it only covers a small region of
COSMOS, MUSE has the unique advantage of providing spectral information over
the entire field, without the need of target pre-selection. This gives an
unbiased detection of all the brightest Ly$\rm \alpha$ emitters among SMUVS
sources, which by design are stellar-mass selected galaxies. Within the studied
area, ~14% of the SMUVS galaxies at z > 2.9 have Ly$\rm \alpha$ fluxes F$\rm
_\lambda$ > 7 x 10$^{-18}$ erg s$^{-1}$ cm$^{-2}$. These Ly$\rm \alpha$
emitters are characterized by three types of emission, 47% show a single line
profile, 19% present a double peak or a blue bump and 31% show a red tail. One
object (3%) shows both a blue bump and a red tail. We also investigate the
spectral energy distribution (SED) properties of the SMUVS MUSE-detected
galaxies and MUSE non-detections. After stellar-mass matching both populations,
we find that MUSE detected galaxies have generally lower extinction than
SMUVS-only objects, while there is no clear intrinsic difference in the mass
and age distributions. For the MUSE-detected SMUVS galaxies, we compare the
instantaneous SFR lower limit given by Ly$\rm \alpha$ flux with its past
average derived from SED fitting, and find evidence for rejuvenation in some of
our oldest objects. We also study the spectra of those Ly$\rm \alpha$ emitters
which are not detected in SMUVS in the same field. We find different
distributions of the emission line profiles, which could be ascribed to the
fainter Ly$\rm \alpha$ luminosities of the MUSE-only sources and an
intrinsically different mass distribution. Finally, we search for the presence
of galaxy associations. MUSE's integral coverage is 20 times more likely to
find associations than all other existing spectral data in COSMOS, biased by
target pre-selection.
