Physical and Chemical Inhomogeneities Inside the Vela SNR Shell: Indications of Ejecta Shrapnels

We present the results of the combined analysis of three XMM-Newton EPIC observations of the northern rim of the Vela supernova remnant (SNR). The three pointings cover an area of gtrsim10 pc² (at 250 pc) behind the main shock front, and we aim to study with high resolution the spatial distribution of the physical and chemical properties of the X-ray-emitting plasma on this large scale. We produce count-rate images and equivalent width maps of the Ne IX and Mg XI emission blends. We also perform a spatially resolved spectral analysis of a set of physically homogeneous regions. We reveal physical and chemical inhomogeneities in the X-ray-emitting plasma. In particular, we find large variations of the O, Ne, Mg, and Fe abundances. In some bright knots, we also find unexpectedly enhanced Ne and Mg abundances, with values significantly larger than solar. Our results support a possible association of a few X-ray-emitting knots with previously undetected residuals of stellar fragments (i.e., shrapnels) observed, in projection, inside the Vela shell.