The Reservoir of the Per-emb-2 Streamer

Abstract

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 (HC3N, HC5N, 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 ( nH2≈1.9×104 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/HC3N 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) × 105 yr, suggesting that the mass accretion via the streamer would continue until the end of the Class I stage.