QSOs Associated with M82

Abstract

The starburst/AGN galaxy M82 was studied by Dahlem, Weaver, and Heckman using X-ray data from ROSAT and ASCA as part of their X-ray survey of edge-on starburst galaxies. They found 17 unresolved hard X-ray sources around M82, in addition to its strong nuclear source, and other X-rays within the main body of M82. We have measured optical point sources at these positions and have obtained redshifts of six candidates at the Keck I 10 m telescope, using the low-resolution imaging spectrograph (LRIS). All six are highly compact optical and X-ray objects with redshifts ranging from 0.111 to 1.086. They all show emission lines. The three with the highest redshifts are clearly QSOs. The others with lower redshifts may be either QSOs or compact emission-line galaxies. In addition to these six, there are nine QSOs lying very close to M82 which were discovered many years ago. There is no difference between optical spectra of these latter QSOs, only two of which are known to be X-ray sources, and the X-ray-emitting QSOs. The redshifts of all 15 range between 0.111 and 2.05. The large number of QSOs and their apparent association with ejected matter from M82 suggest that they are physically associated with the galaxy and have large intrinsic redshift components. If this is correct, the absolute magnitudes lie in the range -8 < Mv < -10. Also, we speculate that the luminous variable X-ray source which has been detected by Chandra in the main body of M82 some 9'' from the center is another QSO in the process of ejection from the nucleus, and we propose some observational tests of this hypothesis.