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

Abstract

We identify an abundant population of extreme emission-line galaxies (EELGs) at redshift z ∼ 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 [O III] emission lines - with rest-frame equivalent widths ∼1000 Å- in the four candidates that have HST/WFC3 grism observations, we conclude that these objects are galaxies with ∼108 M⊙ in stellar mass, undergoing an enormous starburst phase with M*/M *;̇of only ∼15Myr. 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 × 10-4 Mpc-3) can produce in ∼4Gyr much of the stellar mass density that is presently contained in 10 8-109 M⊙ 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. © 2011. The American Astronomical Society. All rights reserved.