Circumstellar Chemistry

The SMA IRC+10216 line survey is the first interferometric line survey. Spatial information of the distribution of molecules is one of the important products of this survey. This will allow comparison with model calculations of abundances as a function of radius and improve our understanding of circumstellar chemistry. There is also a potential of discovering new molecules. As yet, there are about 200 lines that remain unassigned to known entries in spectral line catalogs.

Some sample spectra from the IRC+10216 line survey are shown in Figure 5. This is a unique survey carried out with an interferometer, providing information on the spatial distribution of the emission in each detected line. Figures 6 and 7 show examples of some of the lines showing extended emission.

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Figure 5: Sample spectrum from the beginning and end regions of the 294-355 GHz range of frequencies covered by the SMA line-survey of IRC+10216. The spectrum is obtained from the integrated flux over a 2" x 2" region toward the center (peak continuum). Blue and Red spectra are scaled down in y-axis by a factor of 3 and 40, respectively (Patel et al. 2011).

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Figure 6: HC3N (integrated) emission toward IRC+10216, showing spatially resolved complex morphology. The bottom panel shows a portion of the spectrum from the line-survey.

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Figure 7:Ring-like distribution of C4H in IRC+10216. This molecule is created in the outer part of the envelope where the chemistry is influenced by the interstellar UV radiation. The plus symbol indicates the position of the star (from peak of continuum emission).

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