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The ROSAT Deep Survey II. Optical identification, photomettry and spectra of sources in the Lockman field

Maarten Schmidt·Guenther Hasinger·James Gunn·Don Schneider·Richard Burg·Riccardo Giacconi·Ingo Lehmann·John MacKenty·Joachim Truemper·Gianni Zamorani
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Abstract

The ROSAT Deep Survey includes a complete sample of 50 X-ray sources with fluxes in the $0.5 - 2$ keV band larger than 5.5 $10^{-15}$ erg cm$^{-2}$ s$^{-1}$ in the Lockman field (Hasinger et al., Paper I). We have obtained deep broad-band CCD images of the field and spectra of many optical objects near the positions of the X-ray sources. We define systematically the process leading to the optical identifications of the X-ray sources. For this purpose, we introduce five identification (ID) classes that characterize the process in each case. Among the 50 X-ray sources, we identify 39 AGNs, 3 groups of galaxies, 1 galaxy and 3 galactic stars. Four X-ray sources remain unidentified so far; two of these objects may have an unusually large ratio of X-ray to optical flux. Keywords: surveys -- galaxies: active -- quasars: emission lines -- galaxies: Seyfert -- X-rays: galaxies

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Maarten Schmidt, Guenther Hasinger, James Gunn, Don Schneider, Richard Burg, Riccardo Giacconi, Ingo Lehmann, John MacKenty, Joachim Truemper, Gianni Zamorani. 1997-09-15. The ROSAT Deep Survey II. Optical identification, photomettry and spectra of sources in the Lockman field. https://arxiv.org/abs/astro-ph/9709144

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