Imprints of stellar feedback on magnetic fields in the iris nebula NGC 7023

Abstract

We present 850 μm polarized continuum observations carried out using SCUBA-2/POL-2 on the James Clerk Maxwell Telescope toward a reflection nebula, NGC 7023. The nebula is powered by the Herbig Ae Be star HD 200775 and also forms a hub in the hub-filament cloud, LDN 1172/1174. We detect submillimeter emission to the north and east of the location of the central star. The magnetic field (B-field) morphology is found to be curved and follows the clump morphology. The comparison of the B-field morphology at the clump scales (∼0.02 pc) derived using POL-2 data with that of the envelope scale (∼0.5 pc) derived using archival Planck/optical polarimetric observations suggests that the field lines are not preserved from envelope to clump scales. We suggest that this reordering of the magnetic field lines could be due to the interaction with the already evolved high-velocity outflow gas around the central star, which hints at the presence of outflow feedback. We estimated a B-field strength of 179 ± 50 μG in the starless core, and 121 ± 34 μG and 150 ± 42 μG in the protostellar cores, using the N2H+ (1–0) line observed with the 13.7 m single-dish telescope at the Taeduk Radio Astronomy Observatory (TRAO). The stability analysis gives magnetically subcritical values, while the magnetic, gravitational, and outflow kinetic energies are roughly balanced. Our study unveils the first possible evidence for magnetic field lines being shaped by outflow feedback in the vicinity of a photodissociation region driven by an intermediate-mass, pre-main-sequence star.