Robert M. Loughnane, Matt P. Redman, Eric R. Keto, Nadia Lo, Maria R. Cunningham
Although hydrogen cyanide has become quite a common molecular tracing species
for a variety of astrophysical sources, it, however, exhibits dramatic non-LTE
behaviour in its hyperfine line structure. Individual hyperfine components can
be strongly boosted or suppressed. If these so-called hyperfine line anomalies
are present in the HCN rotational spectra towards low or high mass cores, this
will affect the interpretation of various physical properties such as the line
opacity and excitation temperature in the case of low mass objects and infall
velocities in the case of their higher mass counterparts. This is as a
consequence of the direct effects that anomalies have on the underlying line
shape, be it with the line structural width or through the inferred line
strength. This work involves the first observational investigation of these
anomalies in two HCN rotational transitions, J=1!0 and J=3!2, towards both low
mass starless cores and high mass protostellar objects. The degree of anomaly
in these two rotational transitions is considered by computing the ratios of
neighboring hyperfine lines in individual spectra. Results indicate some degree
of anomaly is present in all cores considered in our survey, the most likely
cause being line overlap effects among hyperfine components in higher
rotational transitions.
View original:
http://arxiv.org/abs/1112.1743
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