The evolution of the equivalent width of the Ha emission line and specific star formation rate in star-forming galaxies at 1 < z < 5

We present the results of a study which uses spectral energy distribution (SED) fitting to investigate the evolution of the equivalent width (EW) of the H... emission line in star-forming galaxies over the redshift interval 1 < z < 5. After first demonstrating the ability of our SED-fitting technique to recover EW(H...) using a sample of galaxies at z ... 1.3 with EW(H...) measurements from 3D-HST grism spectroscopy, we proceed to apply our technique to samples of spectroscopically confirmed and photometric-redshift selected star-forming galaxies at z greater than or equal to 1 in the CANDELS (Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey) UDS and GOODS-S fields. Confining our analysis to a constant stellar mass range (9.5 < log...(M*/M...) < 10.5), we find that the median EW(H...) evolves only modestly with redshift, reaching a rest-frame value of EW(H...) =301 plus or minus 30...A by redshift z ... 4.5. Furthermore, using estimates of star formation rate (SFR) based on both UV luminosity and H... line flux, we use our galaxy samples to compare the evolution of EW(H...) and specific star formation rate (sSFR). Our results indicate that over the redshift range 1 < z < 5, the evolution displayed by EW(H...) and sSFR is consistent, and can be adequately parametrized as ... (1 + z) super( 1.0 plus or minus 0.2). As a consequence, over this redshift range, we find that the sSFR and rest-frame EW(H...) of star-forming galaxies with stellar masses M* ...1010M... (ProQuest: ... denotes formulae/symbols omitted.)