Highlights - 09 April 2010 (vol. 512-513)


HIGHLIGHTS: this week in A&A

09 April 2010 (vol. 512-513)


In section 1. Letters

“Detection of CO in Triton's atmosphere and the nature of surface-atmosphere interactions”, by E. Lellouch, C. de Bergh, B. Sicardy, S. Ferron, and H.-U. Käufl, A&A 512, L8

Triton is a moon of Neptune thought to be a captured Kuiper belt object. It possesses a thin, seasonally variable atmosphere mainly made of N2 in equilibrium with the cold surface ices. Using CRIRES at the VLT, Lellouch et al. have been able to detect for the first time the atmosphere in the infrared. This allows the first detection of CO gas in this moon, as well as evidence that the CH4 partial pressure has greatly increased since Voyager times, a likely consequence of Triton's summer solstice in 2000. The ability to make regular ground-based observations of these distant icy bodies offers the possibility of improving how these bodies and their intriguing atmospheres are understood. The European Southern Observatory has issued a press release based on these results.


In section 6. Interstellar and circumstellar matter

“Comparing the statistics of interstellar turbulence in simulations and observations. Solenoidal versus compressive turbulence forcing”, by C. Federrath, J. Roman-Duval, R. Klessen, W. Schmidt, and M.-M. Mac Low, A&A 512, A81

The authors model two extreme cases of external forcing for turbulence in non-selfgravitating isothermal interstellar clouds using the FLASH3 hydrodynamic code. They show model results for a variety of diagnostics (e.g. structure functions, probability density functions, principal component analysis, and Delta variance), all techniques that have been employed for observations of cloud structure. The dispersion of the density probability distribution is not only a function of the RMS Mach number, but it also depends on the nature of the turbulence forcing. All the analytical models above rely on integrals over the density PDF. Since the dispersion of the density PDF depends on how the turbulence is driven, the authors conclude that star formation properties derived in those analytical models are strongly affected by the assumed turbulence-forcing mechanism.  


In section 6. Interstellar and circumstellar matter

“3D model of bow shocks”, by M. Gustafsson, T. Ravkilde, L.E. Kristensen, S. Cabrit, D. Field, and G. Pineau des Forets, A&A 513, A5

Interstellar bow shocks are observed in many outflows originating from young stellar objects. In this work, the authors present molecular bow-shock models calculated with very detailed chemistry. They study the effect of different orientations of the magnetic field and explore several emission line diagnostics. Finally, the models are compared to an observed bow shock in OMC1.


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