The intrinsic luminosity function and evolution of highly beamed active galactic nuclei

Mihai Cara, Purdue University

Abstract

The apparent luminosity and redshift distributions called “luminosity functions” (LF) of highly beamed extragalactic radio sources (blazars) are affected by observational biases, among which Doppler boosting plays an important role. In this work we determine the radio LF of the parent population of core-selected blazars from the MOJAVE (Monitoring O f Jets in Active galactic nuclei with VLBA Experiments) sample by fitting a Doppler boosted model LF to the data. The approach adopted in this work is different from previous studies since it does not make an assumption about the parent population of quasars and blazars, and was possible only with the advent of the statistically complete core-selected samples of active galactic nuclei (AGN), the MOJAVE sample being the first of its kind in this category. We find that the previously proposed forms of evolution of the LF do not provide a good fit without a modification that removes a predicted large spike in the redshift distribution of quasars at small redshifts in the case of steep luminosity distributions. We compare the space densities derived from the MOJAVE LF with previous estimates from the analysis of Fanaroff-Riley type II galaxies and X-ray selected AGN. We find that a good agreement can be obtained if a higher value of the lower luminosity than the one obtained in this work is used for computation of the space densities. We conclude that this is likely due to a break in the parent LF below the luminosity range of the MOJAVE survey. A fainter sample is necessary to reliably determine the LF at lower luminosities. We also show that the biases associated with binning can produce breaks in the observed binned LFs that can mimic luminosity evolution and also prompt the use of incorrect model functions. We propose a different method of constructing the binned LFs that avoids these spurious breaks. We also show that the commonly used banded V/Vmax test can mimic the effect of luminosity dependent evolution even when the underlying evolution is luminosity-independent and therefore should not be used to detect luminosity dependence of evolution without a modification described in this work.

Degree

Ph.D.

Advisors

Lister, Purdue University.

Subject Area

Astronomy

COinS