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ROSAT evidence for AGN and superwind activity in NGC6240 and NGC2782
We present ROSAT observations of the starburst galaxy NGC2782 (HRI plusa weak PSPC frame) and the ultraluminous infrared galaxy NGC6240 (PSPC).The (0.1-2.4) keV spectra of both objects appear similar. However, dueto better sampling spectral modeling is only warranted in case ofNGC6240 for which both a single thermal Raymond-Smith model (kT =0.44+/-0.15 keV) or a hybrid model consisting of 80% power-law with thecanonical photon index -1.9 plus 20% Raymond-Smith contribution (kT =0.63+/-0.35 keV) lead to good fits. However, the single thermal modelturns out to be unlikely because it yields a luminosity of 3.810(43) ergs(-1) , which is hard to reach in a starburst superwind-scenario. Thehybrid model leads to a more moderate luminosity of 5.210(42) erg s(-1), of which 1.010(42) erg s(-1) can be attributed to shocked superwindgas. We link the remaining 4.210(42) erg s(-1) powerlaw to an AGNcomponent because the alternative of inverse-compton scattering of theFIR radiation leads to a too low flux when estimated with availabledata. The result appears to be consistent with preliminarily announcedASCA observations. For NGC2782 we find L_x(0.1-2.4 keV) = 410(41) ergs(-1) (within a factor of four) which can be explained by emission froma shocked superwind region with a high preshock density in agreementwith earlier optical evidence for an outflowing supershell.
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