HOW LYMAN ALPHA EMISSION DEPENDS ON GALAXY STELLAR MASS

In this work, we show how the stellar mass (M∗) of galaxies affects the 3 < z < 4.6 Lyα equivalent width (EW) distribution. To this end, we design a sample of 629 galaxies in the M∗ range 7.6 < log M∗/M_⊙ < 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 Lyα fluxes and use 3D-HST/CANDELS ancillary data. In order to study the Lyα 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 = W₀(M∗)^-1A(M∗)e^-EW/W0(M∗). Through a Bayesian analysis, we confirm that lower M∗ galaxies have higher Lyα 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)log M∗/M_⊙ + 3.01(1.2) and W₀(M∗) = - 15.6(3.5)log M∗/M_⊙ + 166(34). These results are crucial for proper interpretation of Lyα emission trends reported in the literature that may be affected by strong M∗ selection biases.