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 (HC${}_3$N, HC${}_5$N, CCH, and CCS) in the 3mm and 7mm bands toward the streamer flowing to the Class 0 young stellar object (YSO) Per-emb-2 with the Nobeyama 45m radio telescope. A region with a diameter of $\sim 0.04$ pc is located north with a distance of $\sim 20,500$ au from the YSO. The streamer connects to this north region which is the origin of the streamer. The reservoir has high density and low temperature ($n_{{\mathrm{H}}_2}\approx 1.9\times 10^4$ cm${}^{-3}$, $T_{\mathrm{kin}}=10$ K), which are similar to those of early stage starless cores. By comparisons with 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${}_{\odot }$. If all of the gas in the reservoir will accrete onto the Per-emb-2 protostellar system, the lifetime of the streamer has been estimated at ($1.1-3.2$)$\times 10^5$ yr, suggesting that the mass accretion via the streamer would continue until the end of the Class I stage.

Accepted for The Astrophysical Journal (ApJ), 18 pages, 10 figures, 6 tables