Calibrating and Extending A Simple Engine Model To Improve Constraints On Quasar Orientation

We use prior work in establishing the simple engine model of quasars, which utilizes two orientation indicators to constrain quasar orientation: projected brighter arm length l_b, and optical core dominance R_v. We then revise the model geometry and then extend it by adding two additional possible orientation indicators and adjusting a prior indicator: we add observed bending angle φ and observed arm length ratio ζ, and change projected brighter arm length l_b to larger arm length l_p. We base our model on assumptions about the distributions of intrinsic parameters of the population of quasars. Under the unification model of all active galactic nuclei, we assume that sources at too high an angle to the line of sight would be seen as radio galaxies, while those at lower angle would be seen as blazars and quasars. By generating a population of quasars from a Monte Carlo simulation and comparing the distribution of observed variables to a lobe-selected sub-sample (LSS), which we assume to be isotropic in orientation (referring to the range of orientations between 0^oand 〖45〗^o to the line of sight for identifying a source as a quasar), we can then adjust the simulation parameters to most accurately reproduce the properties of the LSS. We then test the model parameters and accuracy by selectively using combinations of the indicators to estimate the orientation of the simulation’s own quasars. We find that l_b appears to be a better indicator than l_p, and that φ and ζ do help constrain orientation, but may also cause the estimate to be untrustworthy as the model may simply say that the source is too rare to simulate consistently. We also find that optical core dominance R_v, or the ratio of beamed core luminosity to optical continuum luminosity (R_v=L_core/L_opt), appears to be the most significant indicator of orientation, and that determining the bulk Lorentz factor of the jets, γ, could be significant in adjusting the accuracy of estimates. We then use our model to estimate the orientation of quasars in the LSS. We find that the interquartile range of our estimates is typically about 8^o. Additionally, we find one particular quasar, J1230+3930, which appears to be an abnormally rare source in that it appears implausibly large by our model. Finally, we use our estimates of orientation to calculate the mass of 26 quasars in the LSS, assuming the mass is virialized and for which the relevant data was available. We find that our estimates of black hole mass are about an order of magnitude higher than current estimates.