NEW ACTIVE GALACTIC NUCLEI DETECTED IN ROSAT ALL-SKY SURVEY GALAXIES - 1 - VERIFICATION OF SELECTION STRATEGY

We present the first results of a program to identify so far unknown a ctive nuclei (AGN) in galaxies. Candidate galactic nuclei have been se lected for optical spectroscopy from a cross-correlation of the ROSAT All Sky Survey (RASS) bright source catalog with optical galaxy catalo gs. A high X-ray flux has been used as pointer to galaxies with a high probability to contain active nuclei. Only galaxies have been accepte d for the program for which no activity was noted in NED. For many of the galaxies no radial velocity was reported before. The optical spect ra demonstrate that the galaxies cover a redshift range of 0.014 to 0. 13 and that most of them host active nuclei. For 75% of the 33 candida tes the X-ray emission is caused by the AGN. In addition several of th e remaining candidates host Seyfert 2/LINER nuclei that, however, most certainly cannot explain the X-ray emission alone. Three BL Lac objec ts have been detected serendipitously in galaxy fields that have been followed up by short ROSAT HRI observations to confirm the X-ray galax y identification with improved position accuracy and point response fu nction. The sources show X-ray to radio flux ratios typical for X-ray selected BL Lac objects. The results presented in the paper prove the selection strategy as very successful to detect previously unknown AGN of all Seyfert 1 types in nearby galaxies encouraging the extension o f this program. The detection of new nearby AGN will be used to initia te a detailed investigation of their multi-wavelength properties and a comparison with the more distant AGN population.