DISCOVERY OF MASSIVE, MOSTLY STAR FORMATION QUENCHED GALAXIES WITH EXTREMELY LARGE Lyα EQUIVALENT WIDTHS AT z ∼ 3

We report a discovery of six massive galaxies with both extremely large Ly alpha equivalent widths (EWs) and evolved stellar populations at z similar to 3. These MAssive Extremely STrong Ly alpha emitting Objects (MAESTLOs) have been discovered in our large-volume systematic survey for strong Ly alpha 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 (Ly alpha) similar to 100-300 angstrom, (2) M-star similar to 10(10.5) -10(11.1) M-circle dot, and (3) relatively low specific star formation rates of SFR/M-star similar to 0.03-1 Gyr(-1). Three of the six MAESTLOs have extended Ly alpha 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 Ly alpha 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.