Photoionized Herbig–Haro objects in the Orion Nebula through deep high-spectral resolution spectroscopy – III. HH 514

Abstract

ABSTRACT We analyse the physical conditions and chemical composition of the photoionized Herbig–Haro object HH 514, which emerges from the protoplanetary disc (proplyd) 170-337 in the core of the Orion Nebula. We use high-spectral resolution spectroscopy from Ultraviolet and Visual Echelle Spectrograph at the Very Large Telescope and IFU-spectra from MEGARA at the Gran Telescopio de Canarias. We observe two components of HH 514, the jet base and a knot, with $n_{\rm e}= (2.3 \pm 0.1) \times 10^5 \rm{cm}^{-3}$ and $n_{\rm e}= (7 \pm 1) \times 10^4 \rm{ cm}^{-3}$, respectively, both with Te ≈ 9000 K. We show that the chemical composition of HH 514 is consistent with that of the Orion Nebula, except for Fe, Ni, and S, which show higher abundances. The enhanced abundances of Fe and Ni observed in HH objects compared with the general interstellar medium are usually interpreted as destruction of dust grains. The observed sulphur overabundance (more than two times solar) is challenging to explain since the proplyd photoevaporation flow from the same disc shows normal sulphur abundance. If the aforementioned S-overabundance is due to dust destruction, the formation of sulfides and/or other S-bearing dust reservoirs may be linked to planet formation processes in proplyds, which filter large sulfide dust grains during the accretion of matter from the disc to the central star. We also show that published kinematics of molecular emission close to the central star are not consistent with either a disc perpendicular to the optical jet, or with an outflow that is aligned with it.