Suzaku observation of diffuse X-ray emission from a southwest region of the Carina Nebula

Abstract

Abstract A southwest region of the Carina Nebula was observed with the Suzaku observatory for $47\:$ks in 2010 December. This region shows distinctively soft X-ray emission in the Chandra campaign observations. Suzaku clearly detects the diffuse emission above known foreground and background components between 0.4–$5\:$keV at the surface brightness of $3.3\times 10^{-14}\:$erg$\:$s$^{-1}\:$arcmin$^{-2}$. The spectrum requires two plasma emission components with $kT \sim 0.2$ and $0.5\:$keV, which suffer interstellar absorption of $N_{\,\rm H} \sim 1.9 \times 10^{21}\:$cm$^{-2}$. Multiple absorption models assuming two-temperature plasmas at ionization equilibrium or non-equilibrium are tested but there is no significant difference in terms of $\chi ^{2}/$d.o.f. These plasma temperatures are similar to those of the central and eastern parts of the Carina Nebula measured in earlier Suzaku observations, but the surface brightness of the hot component is significantly lower than those of the other regions. This means that these two plasma components are physically separated and have different origins. The elemental abundances of O, Ne, and Mg with respect to Fe favor that the diffuse plasma originates from core-collapsed supernovae or massive stellar winds.