XMM-Newton observations of NGC 253: Resolving the emission components in the disk and nuclear area

We describe the first XMM-Newton observations of the starburst galaxy NGC 2 53. As known from previous X-ray observations, NGC 253 shows a mixture of e xtended (disk and halo) and point-source emission. The high XMM-Newton thro ughput allows a detailed investigation of the spatial, spectral and variabi lity properties of these components simultaneously. We characterize the bri ghtest sources by their hardness ratios, detect a bright X-ray transient si milar to 70" SSW of the nucleus, and show the spectrum and light curve of t he brightest point source ( similar to 30" SSW of the nucleus, most likely a black-hole X-ray binary, BHXRB). The unresolved emission of two disk regi ons can be modeled by two thin thermal plasma components (temperatures of s imilar to0.13 and 0.4 keV) plus residual harder emission: with the lower te mperature component originating from above the disk. The nuclear spectrum c an be modeled by a three temperature plasma (similar to0.6, 0.9, and 6 keV) with the higher temperatures increasingly absorbed. The high temperature c omponent most likely originates from the starburst nucleus, as no non-therm al component, that would point at a significant contribution from an active nucleus (AGN), is needed. Assuming that typeIIa supernova remnants (SNRs) are mostly responsible for the E > 4 keV emission, the detection with EPIC of the 6.7 keV line allows us to estimate a supernova rate within the nucle ar starburst of 0.2 yr(-1) The unprecedented combination of RGS and EPIC al so sheds new light on the emission of the complex nuclear region, the X-ray plume and the disk diffuse emission. In particular, EPIC images reveal tha t the limb-brightening of the plume is mostly seen in higher ionization emi ssion lines, while in the lower ionization lines, and below 0.5 keV, the pl ume is more homogeneously structured. The plume spectrum can again be model ed by a three temperature thermal plasma containing the two low temperature nuclear components (though less absorbed) plus an unabsorbed 0.15 keV comp onent similar to the disk spc ci-ra. This points to new interpretations as to the make up of the starburst-driven outflow.