  In this work, we show how the stellar mass (M) of galaxies affects the
3<z<4.6 Ly-alpha equivalent width (EW) distribution. To this end, we design a
sample of 629 galaxies in the M range 7.6 < logM/Msun < 10.6 from the
3D-HST/CANDELS survey. We perform spectroscopic observations of this sample
using the Michigan/Magellan Fiber System, allowing us to measure Ly-alpha
fluxes and use 3D-HST/CANDELS ancillary data. In order to study the Ly-alpha EW
distribution dependence on M, we split the whole sample in three stellar mass
bins. We find that, in all bins, the distribution is best represented by an
exponential profile of the form dN(M)/dEW= A(M)exp(-EW/W0(M))/W0(M). Through a
Bayesian analysis, we confirm that lower M galaxies have higher Ly-alpha EWs.
We also find that the fraction A of galaxies featuring emission and the
e-folding scale W0 of the distribution anti- correlate with M, recovering
expressions of the forms A(M)= -0.26(.13) logM/Msun+3.01(1.2) and W0(M)=
-15.6(3.5) logM/Msun +166(34). These results are crucial for proper
interpretation of Ly-alpha emission trends reported in the literature that may
be affected by strong M selection biases.
