The Influence of Massive Stars in the Interstellar Medium of IC 1613: The Supernova Remnant S8 and the Nebula S3 Associated with a WO Star

Abstract

We present a detailed kinematic analysis of two selected nebulae in the Local Group irregular galaxy IC 1613. The nebulae are S8, the only known supernova remnant in this galaxy, and S3, a Wolf-Rayet nebula associated with the only WO star in this galaxy. For S8 we have obtained and analyzed its radial velocity field, where we found complex profiles that can be fitted by several velocity components. These profiles also show the presence of high-velocity, low-density gas. From this we have obtained the expansion velocity, estimated the preshock density, and calculated the basic kinematic parameters of this supernova remnant (SNR). We suggest that in S8 we are seeing an SNR partially hidden by dust. This suggestion comes from the fact that the SNR is located between two superbubbles where a ridge of obscured material reveals the existence of dust. Moreover, we show that this hypothesis prevails when arguments based on energy are taken into account. In the case of S3 this nebula shows bipolar structure. By using its kinematics, we have analyzed its two lobes and its waist, as well as its relation with the nearest superbubbles. For the first time we are able to see that the northwestern lobe is closed, showing a cloverleaf shape. This fact allows us to obtain a better quantitative knowledge of the nebula as a whole. Furthermore, we found evidence of expansion in the northwestern lobe. In the light of our results, we can state that these nebulae are the product of very massive stellar evolution. The influence these stars still have in shaping their surrounding gas is surprising and so is the energy liberated to the interstellar medium of this galaxy.