Confirmation of small dynamical and stellar masses for extreme emission line galaxies at z ∼ 2

Spectroscopic observations from the Large Binocular Telescope and the Very Large Telescope reveal kinematically narrow lines (∼50 km s^-1) for a sample of 14 extreme emission line galaxies at redshifts 1.4 < z < 2.3. These measurements imply that the total dynamical masses of these systems are low (≲ 3 × 10⁹ M_⊙). Their large [O III] λ 5007 equivalent widths (500-1100 Å) and faint blue continuum emission imply young ages of 10-100 Myr and stellar masses of 10 ⁸-10⁹ M _⊙, confirming the presence of a violent starburst. The dynamical masses represent the first such determinations for low-mass galaxies at z > 1. The stellar mass formed in this vigorous starburst phase represents a large fraction of the total (dynamical) mass, without a significantly massive underlying population of older stars. The occurrence of such intense events in shallow potentials strongly suggests that supernova-driven winds must be of critical importance in the subsequent evolution of these systems.