Photoionized Herbig-Haro objects in the Orion Nebula through deep high-spectral resolution spectroscopy III: HH514

TL;DR

This study investigates the physical conditions and chemical composition of the Herbig-Haro object HH 514 in the Orion Nebula, revealing insights into dust destruction, chemical abundances, and kinematics of the jet and surrounding material.

Contribution

It provides detailed spectroscopic analysis of HH 514, highlighting unusual sulfur abundance and challenging existing models of outflow alignment and dust processing in protoplanetary environments.

Findings

HH 514 has electron densities of 2.3×10^5 and 7×10^4 cm^-3 for jet base and knot.

Chemical composition is similar to Orion Nebula except for Fe, Ni, and S.

Sulfur overabundance suggests dust destruction linked to planet formation processes.

Abstract

We analyze the physical conditions and chemical composition of the photoionized Herbig-Haro object HH~514, which emerges from the proplyd 170-337 in the core of the Orion Nebula. We use high-spectral resolution spectroscopy from UVES 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 $n_{\rm e}= (2.3 \pm 0.1) \times 10^5 \text{cm}^{-3}$ and $n_{\rm e}= (7 \pm 1) \times 10^4 \text{cm}^{-3}$, respectively, both with $T_{\rm e}\approx 9000 \text{ K}$. 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 is 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 disk 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 protoplanetary disks, which filter large sulfide dust grains during the accretion of matter from the disk to the central star. We also show that published kinematics of molecular emission close to the central star are not consistent with either a disk perpendicular to the optical jet, nor with an outflow that is aligned with it.