Star formation in galaxies at z~4-5 from the SMUVS survey: a clear starburst/main-sequence bimodality for Halpha emitters on the SFR-M* plane

Understand

We study a large galaxy sample from the Spitzer Matching Survey of the UltraVISTA ultra-deep Stripes (SMUVS) to search for sources with enhanced 3.6 micron fluxes indicative of strong Halpha emission at z=3.9-4.9.

• We find that the percentage of &#34;Halpha excess&#34; sources reaches 37-40% for galaxies with stellar masses log10(M*/Msun) ~ 9-10, and decreases to <20% at log10(M*/Msun) ~ 10.7.
• At higher stellar masses, however, the trend reverses, although this is likely due to AGN contamination.
• We derive star formation rates (SFR) and specific SFR (sSFR) from the inferred Halpha equivalent widths (EW) of our &#34;Halpha excess&#34; galaxies.