Maximum Likelihood Models for the X-ray Luminosity Function of Active Galactic Nuclei
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**Session 19 -- Multiwavelength AGN Studies**
*Display presentation, Monday, 9, 1995, 9:20am - 6:30pm*

## [19.04] Maximum Likelihood Models for the X-ray Luminosity Function of Active Galactic Nuclei

*D.A. Schwartz (SAO), R.M. Hively (Earlham College), W.H. Tucker (SAO)*
Maximum likelihood methods are utilized to derive evolutionary
luminosity functions for X-ray selected AGN's from the Einstein
Extended Medium Sensitivity Survey. Our analysis is unique in that 1.
We require our model of evolution to be consistent with physical
continuity of the numbers of AGN, 2. We use maximum likelihood to
determine the values of all free parameters simultaneously, and 3. We
use Monte Carlo simulations to determine the absolute statistical
significance of our best fit parameters. The last point corrects
errors one would make if they used Komolgorov-Smirov confidence limits
without considering that they have first obtained the best-fit to the
free parameters. Assuming an initial power law luminosity function,
we find that we require breaks at low and high luminosities. Assuming
that the luminosity of an individual AGN changes with time as a power
law proportional to the current AGN luminosity, we rule out power law
indices of either 1.0 (the "pure luminosity evolution" case) or 1.5.
Those two indices have been predicted from specific physical models.
We will also discuss implications for the fraction of the X-ray
background produced by AGN.

**Monday
program listing**