2008ApJ...675..389M -
Astrophys. J., 675, 389-404 (2008/March-1)
Small-scale behavior of the physical conditions and the abundance discrepancy in the Orion nebula.
MESA-DELGADO A., ESTEBAN C. and GARCIA-ROJAS J.
Abstract (from CDS):
We present the results of long-slit spectroscopy, in several positions, of the Orion Nebula. Our goal is to study the spatial distributions of a large number of nebular quantities, including line fluxes, physical conditions, and ionic abundances, at a spatial resolution of about 1". In particular, we have compared the O++ abundance determined from collisionally excited and recombination lines in 671 individual one-dimensional spectra covering different morphological zones of the nebula. We find that protoplanetary disks (proplyds) show prominent spikes of Te N II, which is probably produced by collisional deexcitation due to the high electron densities found in these objects. Herbig-Haro objects show also relatively high values of Te N II, but these are probably produced by local heating due to shocks. We also find that the spatial distribution of the pure recombination O II and [O III] lines is fairly similar. The abundance discrepancy factor (ADF) of O++ remains rather constant along the slit positions, except in some particular small areas of the nebula, such as at the locations of the most conspicuous Herbig-Haro objects. There is also an apparent slight increase of the ADF in the inner 40" around θ1 Ori C. We find a negative radial gradient of Te O III and TeN II in the nebula, based on the projected distance from θ1 Ori C. In addition, the ADF of O++ seems to increase very slightly with the electron temperature. Finally, we estimate the value of the mean-square electron temperature fluctuation, the so-called t2 parameter. Our results indicate that the hypothetical thermal inhomogeneities, if they exist, should be smaller than our spatial resolution element.
Abstract Copyright:
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Journal keyword(s):
ISM: H II Regions - ISM: Abundances - ISM: Individual: Name: Orion Nebula
Errata:
erratum vol. 685, p. 679 (2008)
CDS comments:
Standard star H600 = Hilt 600
Simbad objects:
20
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