Diffuse far-ultraviolet observations of the Lupus Loop region

Abstract

Diffuse far-ultraviolet emissions from the Lupus Loop region have been observed with the SPEAR/FIMS instrument. We have detected several important ionic lines, including Si II*, C IV, and N IV], which characterize the warm and hot ionized gas in this region. The spatial variations in the line intensities of Si II* and C IV have also been studied in comparison with X-ray and dust observations. The result shows that they originate from the interface between the hot gas seen in X-rays and the cooler H I shell with which dust is associated. The interface is rather diffuse, and gases with different temperatures seem to coexist in this region. A shock may exist up front in the interface, but its velocity should be very small, as no shock-related distinguishing feature is seen in H alpha.