  We measured the electronic structure of an iron arsenic parent compound
LaFeAsO using angle resolved photoemission spectroscopy (ARPES). By comparing
with a full-potential Linear Augmented PlaneWave calculation we show that the
extra large Gamma hole pocket measured via ARPES comes from electronic
structure at the sample surface. Based on this we discuss the strong
polarization dependence of the band structure and a temperature-dependent
hole-like band around the M point. The two phenomena give additional evidences
for the existence of the surface-driven electronic structure.
