“School of Astronomy”
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| Paper IPM / Astronomy / 18199 |
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We carried out a sensitive survey of C and C using the EDIBLES data set. We also expanded our searches to C, C, and CC isotopologue in the most molecule-rich sightlines.
We fit synthetic spectra generated following a physical excitation model to the C (2-0) Phillips band to obtain the C column density () as well as the kinetic temperature () and number density () of the host cloud. The C molecule was measured through its (000-000) electronic origin band system. We simulated the excitation of this band with a double-temperature Boltzmann distribution.
We present the largest combined survey of C and C to date in which the individual transitions can be resolved. In total we detected C in 51 velocity components along 40 sightlines, and C in 31 velocity components along 27 sightlines. The two molecules are detected in the same velocity components. We find a very good correlation between (C) and (C) with Pearson and an average (C)/(C) ratio of 15.51.4. A comparison with the behaviour of the C DIBs shows that there are no clear differences among sightlines with and without detection of C and C. This is in direct contrast to the better-studied non-C DIBs who have reduced strengths in molecule-rich environments. We also identify for the first time the (2), (3), and (4) transitions of the CC (2-0) Phillips band in a stacked average spectrum, and estimate the isotopic ratio of carbon C/C as 798. Our search for the C and C optical bands was unsuccessful.
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