3D Observations of the nebula N30 in the LMC

Extract

N30 is a 80×330 pc nebula, seen in projection to the North of the LMC. At the position of the nebula, the neutral HI gas is distributed within two layers, with respective heliocentric velocities of 303 km s⁻¹ for the major disk component, and 285 km s⁻¹ for the low-velocity component (Luks & Rohlf 1992). The respective positions of the HI components along the line of sight are not known, nor is the distance between the HI layers, nor their thickness. N30 has been observed with the “survey Hα” equipment of the Observatoire de Marseille (see Rosado et al, and Marcelin et al.,this meeting), giving a 38’ square field (spatial resolution of 9“×9”) and using two scanning Fabry-Perot interferometers, the first one having a spectral sampling step of 15.7 km s⁻¹, and the second one of 4.8 km s⁻¹. No splitting of the line profile is visible, excluding large inner motions. The main emissions measured in N30 and also in all its 8 nearby bright and faint nebulae have heliocentric velocities in the range 302-315 km s⁻¹. Such a velocity shows that all the nebulae are situated inside the HI disk component, following their exciting stars.