Extreme emission-line galaxies in CANDELS : broadband-selected, starbursting dwarf galaxies at z > 1

We identify an abundant population of extreme emission-line galaxies (EELGs) at redshift z similar to 1.7 in the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey imaging from Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3). Sixty-nine EELG candidates are selected by the large contribution of exceptionally bright emission lines to their near-infrared broadband magnitudes. Supported by spectroscopic confirmation of strong [OIII] emission lines-with rest-frame equivalent widths similar to 1000 angstrom-in the four candidates that have HST/WFC3 grism observations, we conclude that these objects are galaxies with similar to 10(8) M-circle dot in stellar mass, undergoing an enormous starburst phase with M-*/(M) over dot(*) of only similar to 15 Myr. These bursts may cause outflows that are strong enough to produce cored dark matter profiles in low-mass galaxies. The individual star formation rates and the comoving number density (3.7 x 10(-4) Mpc(-3)) can produce in similar to 4 Gyr much of the stellar mass density that is presently contained in 10(8)-10(9) M-circle dot dwarf galaxies. Therefore, our observations provide a strong indication that many or even most of the stars in present-day dwarf galaxies formed in strong, short-lived bursts, mostly at z > 1