S18A0018abst
S18A0018
We have recently discovered six “MAssive Extremely STrong Lymanα Objects (hereafter MAESTLOs)” at z ∼ 3 in the COSMOS field using our Suprime-Cam imaging survey with 12 intermediate band filters. The MAESTLOs have the following properties; 1) large stellar mass of Mstar >1010.5 M⊙, 2) extremely strong Lyα emission of EW0(Lyα) > 100 Å, 3) their Lyα emission tends to be spatially extended with rhl ∼ 4–7 kpc, although the rest-UV continuum images show a very compact morphology, 4) old stellar population indicated by strong Balmer/4000 Å break, and 5) no evidence for AGN. These suggest that MAESTLOs are in the final stage of massive galaxy formation where their SFRs decrease as gas is ejected from the galaxy by the superwind-driven outflows. In S16B, we observed 5 out of the 6 MAESTLOs with FOCAS in the poor seeing condition and confirmed their redshifts, but could not study the detailed Lyα profiles. We here propose follow-up observations of these MAESTLOs with DEIMOS to test this scenario by examining the detailed Lyα line profiles and measuring the line flux ratios among NV, CIV, HeII, and Lyα. The proposed observations provide us important clues to understand the quenching of the star formation in massive galaxies at the cosmic noon.
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