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Detection of inters...
Abstract
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- We report the detection of absorption from interstellar C2 and C3 towards the moderately reddened star Sk 143, located in the near `wing' region of the SMC, in optical spectra obtained with the European Southern Observatory Very Large Telescope (VLT)/Ultraviolet and Visual Echelle Spectrograph. These detections of C2 (rotational levels J = 0-8) and C3 (J = 0-12) absorption in the SMC are the first beyond our Galaxy. The total abundances of C2 and C3 (relative to H2) are similar to those found in diffuse Galactic molecular clouds - as previously found for CH and CN - despite the significantly lower average metallicity of the Small Magellanic Cloud. Analysis of the rotational excitation of C2 yields an estimated kinetic temperature Tk ˜ 25 K and a moderately high total hydrogen density nH ˜ 870 cm-3 - compared to the T01 ˜ 45 K and nH ˜ 85-300 cm-3 obtained from H2. The populations of the lower rotational levels of C3 are consistent with an excitation temperature of about 34 K.
Subject headings
- NATURVETENSKAP -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)
Keyword
- galaxies: Interstellar matter
- Interstellar matter: molecules
- Magellanic Clouds
- Interstellar matter: lines and bands
Publication and Content Type
- art (subject category)
- ref (subject category)
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