Extreme Emission-line Galaxies in CANDELS: Broadband-selected, Starbursting Dwarf Galaxies at z > 1
Wuyts, S.; Jahnke, K.; Dickinson, M.; Ferguson, H. C.; Finkelstein, S. L.; Dunlop, J. S.; Huang, K. -H.; Koekemoer, A. M.; Rix, H. -W.; Faber, S. M.; van der Wel, A.; Scarlata, C.; Weiner, B. J.; Ashby, M. L. N.; Bell, E. F.; Koo, D. C.; Willner, S. P.; Grogin, N. A.; Hathi, N. P.; Trump, J. R.; Guo, Yicheng; Kocevski, D. D.; Riess, A. G.; Rodney, S. A.; Newman, J. A.; Lee, K. -S.; Barro, G.; McGrath, E. J.; Straughn, A. N.; Salmon, B. W.; de Mello, D. F.; Lai, K.
Germany, United States, United Kingdom
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_*/\dot{M}_* of only ~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 × 10-4 Mpc-3) can produce in ~4 Gyr much of the stellar mass density that is presently contained in 108-109 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.