Suzaku and Chandra study of diffuse X-ray emission from the massive star-forming region RCW 38

Abstract

In some massive star-forming regions, diffuse X-ray emission has been observed. It can be classified as thermal emission from sub- or several-keV plasmas, non-thermal emission represented by the power law, or a mixture of them. We have studied the nearby (∼1.7 kpc) young massive star-forming region RCW 38. In a previous study, non-thermal diffuse X-ray emission of 1.25 × 1.75 pc (∼2${_{.}^{\prime}}$5 × 3${_{.}^{\prime}}$5) was reported from Chandra observation. We observed the same region for 72 ks with Suzaku which has a low background and is highly sensitive to spatially extended emission. To detect and consider point source contributions, we also used Chandra data. We divided the area according to the radius from the cluster center. In the inner region (r < 2${_{.}^{\prime}}$0), the existence of the non-thermal component (power law, Γ = 1.7 ± 0.4) was suggested although a two-temperature thermal model (kT = 0.90 ± 0.07 and $6.2^{+7.7}_{-2.3}\:$keV) could not be rejected. In the outer region (r = 2${_{.}^{\prime}}$0–5${_{.}^{\prime}}$5), a two-temperature (kT = 0.95 ± 0.10 and 4.8 ± 0.6 keV) thermal plasma model was favorable. In this paper, the origin of the diffuse X-ray emission is discussed in the context of non-thermal/thermal emission and energetics.