Unveiling Stellar Feedback and Cloud Structure in the <i>ρ</i> Ophiuchi-A Region Using ALMA and JWST: Discovery of Substellar Cores, C ¹⁸ O Striations, and Protostellar Outflows

Abstract In clustered star-forming regions, stellar feedback, such as H ii regions/photon-dominated regions (PDRs), and protostellar jets/outflows, shapes cloud structures and influences star formation. Using high-resolution Atacama Large Millimeter/submillimeter Array millimeter and JWST infrared data, we analyze the cloud structure and the impact of stellar feedback in the nearest dense cluster-forming region Ophiuchi (Oph) A. All six known Class 0/I and two of the six flat-spectrum/Class II objects are detected in the 1.3 mm dust continuum. Additionally, we newly detected seven substellar cores, three of which show compact near-infrared emission, suggesting they are young substellar objects. The remaining cores, with masses of ∼10 −2 M ⊙ and mean densities of ∼10 8 cm −3 , are likely gravitationally bound. They appear connected by faint CO finger-like structures extending from the triple Class 0 system Very Large Array (VLA) 1623-2417 Aa+Ab+B, suggesting they may have been ejected from the close binary VLA 1623 Aa+Ab. 12 CO and near-infrared data reveal multiple protostellar outflows. From the comparison, we identified several new outflows/jets and shocked structures associated with the GSS 30 large bipolar bubble. Strong 12 CO emission traces the eastern edge of the Oph A ridge, forming part of the expanding H ii /PDR bubble driven by the nearby Herbig Be star S1. The northern ridge appears “blown out,” with warm gas flowing toward GSS 30, injecting additional turbulent momentum. Several C 18 O striations in the S1 bubble align with magnetic fields, and position–velocity diagrams show wave-like patterns, possibly reflecting magnetohydrodynamic waves. Stellar feedback significantly influences Oph A’s cloud structure.