Discovery of Massive, Mostly Star Formation Quenched Galaxies with Extremely Large Lyα Equivalent Widths at z ∼ 3
Koekemoer, Anton M.; Tresse, Laurence; Schinnerer, Eva; Tasca, Lidia; Fu, Hai; Ilbert, Olivier; Le Fèvre, Olivier; Toft, Sune; McCracken, Henry J.; Kajisawa, Masaru; Renzini, Alvio; Griffiths, Richard E.; Nagao, Tohru; Taniguchi, Yoshiaki; Scoville, Nick Z.; Carollo, Marcella; Sheth, Kartik; Sanders, David B.; Capak, Peter L.; Civano, Francesca; Lilly, Simon; Shioya, Yasuhiro; Kobayashi, Masakazu A. R.; Kovač, Katarina
Japan, United States, Denmark, France, Italy, Switzerland, Germany
Abstract
We report a discovery of six massive galaxies with both extremely large Lyα equivalent widths (EWs) and evolved stellar populations at z ∼ 3. These MAssive Extremely STrong Lyα emitting Objects (MAESTLOs) have been discovered in our large-volume systematic survey for strong Lyα emitters (LAEs) with 12 optical intermediate-band data taken with Subaru/Suprime-Cam in the COSMOS field. Based on the spectral energy distribution fitting analysis for these LAEs, it is found that these MAESTLOs have (1) large rest-frame EWs of EW0 (Lyα) ∼ 100-300 Å, (2) M⋆ ∼ 1010.5-1011.1 M⊙, and (3) relatively low specific star formation rates of SFR/M⋆ ∼ 0.03-1 Gyr-1. Three of the six MAESTLOs have extended Lyα emission with a radius of several kiloparsecs, although they show very compact morphology in the HST/ACS images, which correspond to the rest-frame UV continuum. Since the MAESTLOs do not show any evidence for active galactic nuclei, the observed extended Lyα emission is likely to be caused by a star formation process including the superwind activity. We suggest that this new class of LAEs, MAESTLOs, provides a missing link from star-forming to passively evolving galaxies at the peak era of the cosmic star formation history.
Based on observations with NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555; also based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan; and also based on data products from observations made with ESO Telescopes at the La Silla Paranal Observatory under ESO programme ID 179.A-2005 and on data products produced by TERAPIX and the Cambridge Astronomy Survey Unit on behalf of the UltraVISTA consortium.