B. Beckwinchatz et al., THE GAS-PHASE IRON ABUNDANCE IN HERBIG-HARO OBJECTS, Publications of the Astronomical Society of the Pacific, 106(706), 1994, pp. 1271-1275
Citations number
31
Categorie Soggetti
Astronomy & Astrophysics
Journal title
Publications of the Astronomical Society of the Pacific
The gas-phase abundance ratios Fe/S and Fe/O have been determined for
the Herbig-Haro objects HH 1, HH 7, HH II, HI-I 43A, and ''Burnham's N
ebula'' (HH 255). It is the purpose of this study to decide whether a
sizeable fraction of the Fe in these HH objects is still bound in dust
grains or whether the observed matter has gone through sufficiently f
ast shock waves so that the dust grains have been essentially destroye
d and most of the iron has gone back into the gas phase. We have deter
mined the abundance ratios using statistical equilibrium calculations
for the ions Fe+, S+, and (+). (These are the most abundant ions of th
e elements in question.) Abundance determinations have been made using
homogeneous models of the HH objects for which electron temperatures
and densities have been determined observationally from forbidden line
ratios. The results show that the Fe/S ratio in the objects HH 1, HH
7, HH 11, and HH 43A agrees very well with the Population I abundance
ratio. Only Burnham's Nebula (HH255) shows an Fe/S ratio which is abou
t three times lower indicating a shock-wave history which is quite dif
ferent from that of the other HH objects.