  The accurate measurement of stellar masses over a wide range of galaxy
properties is essential for better constraining models of galaxy evolution.
Emission line galaxies (ELGs) tend to have better redshift estimates than
continuum-selected objects and have been shown to span a large range of
physical properties, including stellar mass. Using data from the 3D-HST
Treasury program, we construct a carefully vetted sample of 4350 ELGs at
redshifts 1.16<z<1.90. We combine the 3D-HST emission line fluxes with far-UV
through near-IR photometry and use the MCSED spectral energy distribution
fitting code to constrain the galaxies' physical parameters, such as their star
formation rate (SFRs) and stellar masses. Our sample is consistent with the z~2
mass-metallicity relation. More importantly, we show there is a simple but
tight correlation between stellar mass and absolute magnitude in a near-IR
filter that will be particularly useful in quickly calculating accurate stellar
masses for millions of galaxies in upcoming missions such as Euclid and the
Nancy Grace Roman Space Telescope.
