Streamers bring gas from outer regions to protostellar systems and could change the chemical composition around protostars and protoplanetary disks. We have carried out mapping observations of carbon-chain species (HC _3 N, HC _5 N, CCH, and CCS) in the 3 mm and 7 mm bands toward the streamer flowing to the Class 0 young stellar object (YSO) Per-emb-2 with the Nobeyama 45 m radio telescope. A region with a diameter of ∼0.04 pc is located to the north at a distance of ∼20,500 au from the YSO. The streamer connects to this northern region, which is its origin. The reservoir has high density and low temperature ( ${n}_{{{\rm{H}}}_{2}}\approx 1.9\times {10}^{4}$ cm ^−3 , T _kin = 10 K), which are similar to those of early-stage starless cores. By comparison of the observed abundance ratios of CCS/HC _3 N to the chemical simulations, the reservoir and streamer are found to be chemically young. The total mass available for the streamer is derived to be 24–34 M _⊙ . It has been estimated that, if all of the gas in the reservoir were to accrete onto the Per-emb-2 protostellar system, the lifetime of the streamer would be (1.1–3.2) × 10 ^5 yr, suggesting that the mass accretion via the streamer would continue until the end of the Class I stage.
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