The role of black hole mass in quasar radio activity
Abstract
We use a homogeneous sample of ~300, 0.3 <~z<~ 3, radio-loud quasars (QSOs) drawn from the FIRST and 2dF QSO surveys to investigate a possible dependence of radio activity on black hole mass. By analysing composite spectra for the populations of radio-quiet and radio-loud QSOs - chosen to have the same redshift and luminosity distributions - we find with high statistical significance that radio-loud quasars are on average associated with black holes of masses ~108.6Msolar, about twice as large as those measured for radio-quiet quasars (~108.3Msolar).
We also find a clear dependence of black hole mass on optical luminosity of the form log(MBH/Msolar)RL= 8.57(+/-0.06) - 0.27(+/-0.06)(MB+ 24.5) and log(MBH/Msolar)RQ= 8.43(+/-0.05) - 0.32(+/-0.06)(MB+ 24.5), respectively, for the cases of radio-loud and radio-quiet quasars. It is intriguing to note that these two trends run roughly parallel to each other, implying that radio-loud quasars are associated to black holes more massive than those producing the radio-quiet case at all sampled luminosities. On the other hand, in the case of radio-loud quasars, we find evidence for only a weak (if any) dependence of the black hole mass on radio power. The above findings seem to support the belief that there exists - at a given optical luminosity - a threshold black hole mass associated with the onset of significant radio activity such as that of radio-loud QSOs; however, once the activity is triggered, there appears to be very little connection between black hole mass and level of radio output.- Publication:
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Monthly Notices of the Royal Astronomical Society
- Pub Date:
- January 2006
- DOI:
- 10.1111/j.1365-2966.2005.09649.x
- arXiv:
- arXiv:astro-ph/0505194
- Bibcode:
- 2006MNRAS.365..101M
- Keywords:
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- black hole physics;
- galaxies: active;
- galaxies: nuclei;
- quasars: general;
- Astrophysics
- E-Print:
- 10 pages, 10 figures, minor changes to match the accepted version