| タイトル | Exocometary Gas in the HD 181327 Debris Ring |
| 著者（英） | Zuckerman, B.; Rodriguez, D.; Roberge, A.; Wyatt, M. C.; Kennedy, G.; Marino, S.; Dent, W. R. F.; Kuchner, M.; Perez, S.; Casassus, S.; Matra, L.; Stark, C. |
| 著者所属（英） | NASA Goddard Space Flight Center |
| 発行日 | 2016-05-23 |
| 言語 | eng |
| 内容記述 | An increasing number of observations have shown that gaseous debris discs are not an exception. However, until now, we only knew of cases around A stars. Here we present the first detection of 12CO (2-1) disc emission around an F star, HD 181327, obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) observations at 1.3 mm. The continuum and CO emission are resolved into an axisymmetric disc with ring-like morphology. Using a Markov chain Monte Carlo method coupled with radiative transfer calculations, we study the dust and CO mass distribution. We find the dust is distributed in a ring with a radius of 86.0 +/- 0.4 au and a radial width of 23.2 +/- 1.0 au. At this frequency, the ring radius is smaller than in the optical, revealing grain size segregation expected due to radiation pressure. We also report on the detection of low-level continuum emission beyond the main ring out to approximately 200 au. We model the CO emission in the non-local thermodynamic equilibrium regime and we find that the CO is co-located with the dust, with a total CO gas mass ranging between 1.2 x 10(exp -6) solar mass and 2.9 x 10(exp -6) solar mass, depending on the gas kinetic temperature and collisional partners densities. The CO densities and location suggest a secondary origin, i.e. released from icy planetesimals in the ring. We derive a CO+CO2 cometary composition that is consistent with Solar system comets. Due to the low gas densities, it is unlikely that the gas is shaping the dust distribution. |
| NASA分類 | Astrophysics; Astronomy |
| レポートNO | GSFC-E-DAA-TN41343 |
| 権利 | Copyright |
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