R. Zentner'
bibliography:
- 'mybib.bib'
title: Biases in the Gravitational Lens Population Induced by Halo and Galaxy Triaxiality
---

Introduction
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Statistics of lensing galaxies have been used as cosmological and galaxy formation probes since early in the modern history of gravitational lensing [@turneretal84]. Lensing rates can be used to constrain dark energy [@fukugitaetal92; @chae03; @mitchelletal05; @chae07; @ogurietal07], to probe the structure of lensing galaxies [@keeton01d; @kochanekwhite01; @chae05], and to probe galaxy evolution [@chaemao03; @ofeketal03; @rusinkochanek05]. While the use of lensing statistics as a cosmological probe has had mixed success, particularly early on, it remains a unique probe with entirely different systematics from more traditional approaches. Consequently, lensing statistics are likely to remain a fundamental cross-check of our understanding of cosmology and galaxy evolution.

One of the difficulties that confronts the study of lensing statistics is that, in general, the halo population that produces gravitational lenses can in fact be a highly biased subsample of the general halo population. For instance, it has long been known that while early type galaxies compose only $\approx 30\%$ of all luminous galaxies, the majority of lensing galaxies are in fact early type since these tend to be more massive and reside in more 