  The one-particle spectral function and its orbital composition are
investigated in a three-orbital model for the undoped parent compounds of the
iron-based superconductors. In the realistic parameter regime, where results
best fit experimental data, it is observed that the magnetization in the xz and
yz orbitals are markedly different and the Fermi surface presents mostly xz
character, as recently observed in photoemission experiments [T. Shimojima et
al., Phys. Rev. Lett. 104, 057002 (2010)]. Since the ferro-orbital order in
this regime is at most a few percent, these results are mainly driven by the
magnetic order. An analogous analysis for a five-orbital model leads to similar
conclusions.
