Recent Observations
made with the BIMA array of the large molecular
cloud towards the hot core in SgrB2 (N-LMH)
have provided a picture of the temperature gradient for the spatial
distribution of three isomers of Glycoladehyde (see figure
1). The
spectra of rotational transitions suggested that the isomers
were
distributed in two distinct regions of the large molecular cloud
that varied with
temperature: the methyl formate and acetic acid isomers were
concentrated
closer to the center of the LMH hot core while the glycoladehyde isomer
was
confined to the outer regions ( ~
50K ) of the LMH (1).
Observations made with the Green
Bank Telescope concentrated on the emissions from the
(808-717) rotational
transitions of glycolaldehyde at 82.4 MHz (2).
This spectra predicted a temperature of ~ 50 K and a peak intensity of
2.5 mK for the glycolaldehyde
population surrounding the LMH hot core.
It also predicted that the populations would be in thermal
equilibrium. The observed peak intensity (30.3mK) was
several orders greater than expected. This suggested a much lower
temperature ~
8K for the glycolaldehyde populations, corresponding to these
transitions. Additionally, prior observations were all
emission spectra while the current lines included emissions and
absorptions
transitions. The transitions were
detected in the k band range, which allows for greater specificity and
clarity
of observed lines than solely relying on millimeter observations. The
subscripts for the k transitions are written along with the J level
transitions: they denote either
emissions or absorptions within the k band.
For example the subscripts in the data set corresponding to the 110
- 101 are emission transitions within
the J=1 level, while 211-202,
312-303
correspond to emission and absorption transitions within the J=2, and J
=3levels. The 413-404
transitions are absorption only. A
comparison of the VLSR velocities and the widths of the
emission /
absorption lines supported the temperature gradient conclusion. The
data suggests a two part cloud with a warmer ~ 50K population which is close to
the LMH source or shock heated surrounded by a halo of colder
populations.
The populations in the The VLSR of the 110-101
transitions suggested that this emission population is cold ~ 8K but
closer to the warmer cloud. The populations in the 211-202,
312-303, and 413-404 transitions
where emission and absorption occurred are further extended. (Data is presented in Table 1)
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