A more detailed analysis will be presented in later papers, when the complete sample of XMM-Newton observations will be available, together with follow-up observations at other wavelengths. In the meantime, the present X-ray catalog provides a basis for future X-ray and optical studies.
Note added in proofs: After acceptance of this manuscript, we obtained the VLT-FORS1 spectrum of NGC 4698-ULX1, that allowed us to identify this source as a background BL Lac object at z=0.43, thus rejecting the classification of that source as a ULX (see Foschini et al., in preparation).
Acknowledgements
This work is based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and the USA (NASA). This research has made use of the NASA's Astrophysics Data System Abstract Service and of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. We acknowledge the partial support of the Italian Space Agency (ASI) to this research.
Copyright ESO 2002