MORIARTY-SCHIEVEN G.H., JOHNSTONE D., BALLY J. and JENNESS T.
Abstract (from CDS):
The L1551 molecular cloud is undergoing a long and sustained period of relatively high efficiency star formation. It contains two small clusters of Class 0 and I protostars, as well as a halo of more evolved Class II and III YSOs, indicating a current and at least one past burst of star formation. We present here new, sensitive maps of 850 and 450 µm dust emission covering most of the L1551 cloud; new CO J=2-1 data of the molecular cloud; and a new, deep, optical image of [S II] emission (6730 Å). Compact submillimeter emitters are concentrated in two subclusters: L1551 IRS5 and L1551 NE, and the HL Tauri group. Both stellar groups show significant extended emission and outflow/jet activity. A jet, terminating at HH 265 and with a very weak associated molecular outflow, may originate from LkHα 358 or from a binary companion to another member of the HL Tauri group. Several Herbig-Haro objects associated with L1551 IRS5/L1551 NE were clearly detected in the submillimeter, as were faint ridges of emission tracing outflow cavity walls. We confirm a large-scale molecular outflow originating from L1551 NE, parallel to that from L1551 IRS5, and suggest that the ``hollow shell'' morphology is more likely due to two interacting outflows. We confirm the presence of a prestellar core (L1551 MC) of mass 2-3 M☉northwest of L1551 IRS5. The next-generation cluster may be forming in this core. The L1551 cloud appears cometary in morphology and appears to be illuminated and eroded from the direction of Orion, perhaps explaining the multiple episodes of star formation.