X-Ray Observations of the W 51 Complex with Suzaku

Abstract

We present a detailed analysis of X-ray emission from the middle-aged supernova remnant W 51 C and star-forming region W 51 B with Suzaku. The soft X-ray emission from W 51 C is well-represented by an optically thin thermal plasma in a non-equilibrium ionization state with a temperature of $ \sim$ 0.7 keV. The elemental abundance of Mg is significantly higher than the solar value. We find no significant feature of an over-ionized plasma in W 51 C. The hard X-ray emission is spatially coincident with the molecular clouds associated with W 51 B, overlapping with W 51 C. The spectrum is represented by an optically thin thermal plasma with a temperature of $ \sim$ 5 keV, or a powerlaw model with a photon index of $ \sim$ 2.2. The emission probably has a diffuse nature, since its luminosity of 1 $ \times$ 10$ ^{34}$ erg s$ ^{-1}$ in the 0.5-10 keV band cannot be explained by any emission from point sources in this region. We discuss the possibility that the hard X-ray emission comes from stellar winds of OB stars in W 51 B, or accelerated particles in W 51 C.