- · Full Refereed Journal Article (PDF/Postscript)
- · Full Refereed Scanned Article (GIF)
- · References in the article
- · Citations to the Article (129) (Citation History)
- · Refereed Citations to the Article
- · SIMBAD Objects (13)
- · Also-Read Articles (Reads History)
- · Translate This Page
We have mapped the Orion-KL region in 28 transitions of 16 molecular
species (H2CO, DCN, HDO, CH3CH2CN,
HC3N, SO2, OCS, 29SiO, SiO, SO,
H13CN, HCN, HCO+, CH3CN,
CH3OH, CO) near 3 millimeters wavelength using the BIMA
array. The maps have 1"-6" angular resolution and 0.3-4 km
s-1 velocity resolution.
The images show two principal molecular concentrations in a ridge of
dense gas, one toward the Kleinmann-Low Nebula (KL), the other
approximately 25" to the northeast, toward dust continuum source CS 1.
The "hot core," "compact ridge," and "plateau" spectral features all are
associated with KL. This region has broad line widths, high-excitation
emission, and unusual chemical abundances; it is associated with
luminous infrared sources, masers, and a powerful bipolar outflow from
at least one embedded young stellar object. By contrast, CS 1 has
narrower line widths, lower temperatures, and only weak indications of
The maps provide evidence that the outflow from KL impacts and heats the
southern edge of CS 1. CH3OH and CH3CN emission
peaks and a cluster of H2O masers are seen here. The outflow
may also be responsible for the velocity divergence of the ridge gas
seen toward KL.
At 1" angular resolution the hot core appears as a chain of dense clumps
offset approximately 1" east of radio continuum source I (IRc2). The
HC3N vibrational excitation temperature in the hot core is
inferred to be 335 K.
The high abundance of HDO, DCN, and other deuterated species in the hot
core indicates evaporation of icy grain mantles. CH3OH,
prominent in the compact ridge, appears to be liberated from the grain
mantles at a lower temperature than H2O, perhaps indicating that it is
selectively evaporated from mixed molecular ices at ˜120 K.
The "plateau" spectral feature looks quite different in different
molecular tracers. Bright SiO v = 0 emission appears to define a 1000 AU
diameter flared disk around radio source I; weaker, thermal SiO emission
appears to fill the infrared cavity around source I. SO and
SO2 form a shell of expanding gas, probably where the outflow
shocks dense clumps along the periphery of the cavity. High-velocity HCN
and HC3N emission seems to trace material ablated from these
The high-velocity outflow probably originates from source I. It does not
appear to be well-collimated, but instead expands in a wide angle cone.
The outflow appears to be partially blocked to the southeast by the hot
In an appendix, we present a table of column densities for each observed
molecular species at nine positions across the source, for comparison
with chemical models. All the maps discussed in this paper are available
in FITS format from the NCSA digital image library.
More Article Retrieval Options
HELP for Article Retrieval