The Gas-Phase Abundances of Heavy Elements and the Destruction of Dust Grains in Herbig-Haro Shock waves

Abstract

view Abstract Citations (24) References (36) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Gas-Phase Abundances of Heavy Elements and the Destruction of Dust Grains in Herbig-Haro Shock waves Beck-Winchatz, Bernhard ; Bohm, Karl-Heinz ; Noriega-Crespo, Alberto Abstract The gas-phase abundance ratios Fe/S and Fe/O have been determined for the Herbig-Haro objects HH 1, HH 7, HH 11, HH 43A, and HH 255 (Burnham's Nebula) from a fairly large number of forbidden emission lines. For HH 1, the ratio Ni/S has been determined as well. Our objective was to investigate whether Fe and Ni are depleted by dust formation in the line-emitting regions as is typical for normal (neutral or molecular) interstellar regions, or whether the observed matter has gone through sufficiently fast shock waves so that the dust grains have been destroyed and Fe and Ni have gone back into the gas phase. Using observationally determined electron temperatures and densities we have solved the statistical equilibrium equations for Fe+, Fe++, S+, 00, 0+, O++, and Ni+ and calculated the intensities of the respective emissions lines. For Fe+ a large number of new collision strengths has recently become available which enabled us to include a much greater number of transitions in our calculations than has previously been possible. For HH 1 and HH 7 both ratios Fe/S and Fe/O agree very well with the solar abundance ratios. For HH 11, the more reliable ratio Fe/S is also very close to the solar value, while the less reliable ratio Fe/O is somewhat higher. For HH 43A both abundance ratios suggest an Fe depletion by a factor 2-3 but the result is considered somewhat uncertain. The results for Burnham's Nebula also indicate a depletion of Fe (by a factor of ∼3) and are more reliable. We conclude that this object has undergone a dust formation and shock wave history which is quite different from that of HH 1, HH 7, and HH 11. The Ni/S abundance ratio determined for HH 1 is a factor ∼10 larger than the solar value. The results for the different observed [Ni II] lines are quite consistent. This situation has been found in other gaseous nebulae as well and is still enigmatic. Publication: The Astronomical Journal Pub Date: January 1996 DOI: 10.1086/117787 Bibcode: 1996AJ....111..346B Keywords: STARS: PRE-MAIN SEQUENCE; ISM: JETS AND OUTFLOWS; ISM: KINEMATICS AND DYNAMICS; SHOCK WAVES full text sources ADS | data products SIMBAD (5)