NCSA Astronomy Digital Image Library
Project Abstract and Description
Structural Details of the Orion Nebula: Detection of a Network of String-like Ionized Features
F. Yusef-Zadeh
Contact: F. Yusef-Zadeh
Email: zadeh@ossenu.astro.nwu.edu
Number of images in project: 1
References: 1990ApJ...361L..19Y
Abstract
The overall morphology of ionized gas at 20 cm wavelength shows a
number of striking new substructures associated with this geometrically
complex HII region. On the largest scale, we find a number of linear
features, which are considered as new ionization fronts, and which form
a 40 degrees angle with respect to the main ionization front known as
the ``bar'' in M42. These features together with the ridge of emission
from the optical bar form a conelike appearance whose 5--10 arcmin
envelope is centered near the Trapezium cluster. On a small scale, we
report the detection of a web of stringlike features with typical
widths of a few arcseconds (approximately 10^16 cm) which are
concentrated throughout the Trapezium region. These features reveal
morphological evidence for production of shocked ionized gas in
star-forming regions, perhaps driven by powerful winds from mass-losing
stars and/or by the shock fronts produced at the edge of expanding HII
regions.
The radio observations were carried out at 20 cm using the VLA in its
A, B, C, and D configurations in 1987 July, 1986 September, 1986
October, and 1986 January, respectively. In order to ensure the lack of
bandwidth smearing of the radio images, the frequency bandwidths used
in these observations were 3.125, 6.25, 12.5, and 25 MHz for the A, B,
C, and D arrays, respectively. The data were self-calibrated, CLEANed
with the AIPS task SDCLN, and mosaicked. The resolution is 1.8 arcsec
by 1.6 arcsec.
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