Dust destruction and thermal inhomogeneities in the Orion Nebula. What can we learn from shocks?
Abstract
We present a long-slit spectroscopic analysis of Herbig-Haro 202 and the surrounding gas of the Orion Nebula using the FORS 1 spectrograph of the Very Large Telescope. Given the characteristics of the Orion Nebula, it is the ideal object to study the mechanisms that play a role in the evolution of H II regions, notably dust destruction by interstellar shocks, which is a poorly understood subject. The use of long-slit allowed us to determine the spatial variation in its physical conditions and chemical abundances; our results are consistent with those of previous studies albeit with improved uncertainties in some determinations. Special attention is paid to Iron (Fe) and Oxygen (O) abundances, which show a peak at the brightest part of HH 202, allowing us to estimate that at least 57% of the dust is the destroyed; we also calculate the amount of depletion of oxygen in dust grains, which amounts to 0.12 ± 0.04 dex. Finally we show that O/H abundances determined from collisionally excited lines and recombination lines are irreconcilable at the center of the shock unless thermal inhomogeneities are considered along the line of sight.
- Publication:
-
Revista Mexicana de Astronomia y Astrofisica Conference Series
- Pub Date:
- July 2017
- Bibcode:
- 2017RMxAC..49..170E