THE VELOCITY STRUCTURE AND TURBULENCE AT THE CENTER OF THE ORION NEBULA

[摘要] Using the Coude Feed System of the Kitt Peak National Observatory at its highest possible dispersion and a CCD detector with wide dynamic range we were able to examine in detail the radial and turbulent velocities of the Orion Nebula at the seeing limit. We were able, for the first time, to resolve multiple components of the spectral lines and fit gaussian profiles to them.Using four different observing runs, two circular areas 2' in diameter were observed, the first centered on $hetasp 1$ Orionis and the second centered on $hetasp 1$ Orionis. The velocity resolution of 1 km ${m s}sp{-1}$ combined with the angular resolution of 2;; allowed us to look in detail at line splitting as well as the location and measurement of high internal motions, about $-50$ km ${m s}sp{-1}$ with respect to the bulk of ionized matter.Because over 900 different positions were measured we were able to use modern statistical techniques for the analysis of turbulence, so that the dispersion relation and the structure function could be calculated and compared with predictions of the Kolmogorov theory.The random motions showed correlation with spatial separation, as expected for turbulence; but, comparison with predictions of the classical theory for nebular turbulence showed poor agreement. If Kolmogorov theory applies, then the energy must be input at many scales.

[发布机构] Rice University

[效力级别] Astrophysics