  Motivated by a recent experiment in which zero-bias peaks have been observed
in scanning tunneling microscopy (STM) experiments performed on chains of
magnetic atoms on a superconductor, we show, by generalizing earlier work, that
a multichannel ferromagnetic wire deposited on a spin-orbit coupled
superconducting substrate can realize a non-trivial chiral topological
superconducting state with Majorana bound states localized at the wire ends.
The non-trivial topological state occurs for generic parameters requiring no
fine tuning, at least for very large exchange spin splitting in the wire. We
theoretically obtain the signatures which appear in the presence of an
arbitrary number of Majorana modes in multi-wire systems incorporating the role
of finite temperature, finite potential barrier at the STM tip, and finite wire
length. These signatures are presented in terms of spatial profiles of STM
differential conductance which clearly reveal zero energy Majorana end modes
and the prediction of a multiple Majorana based fractional Josephson effect. A
substantial part of this work is devoted to a detailed critical comparison
between our theory and the recent STM experiment claiming the observation of
Majorana fermions. The conclusion of this detailed comparison is that although
the experimental observations are not manifestly inconsistent with our
theoretical findings, the very small topological superconducting gap and the
very high temperature of the experiment make it impossible to decisively verify
the existence of a localized Majorana zero mode, as the spectral weight of the
Majorana mode is necessarily spread over a very broad energy regime exceeding
the size of the gap. Thus, although the experimental findings are indeed
consistent with a highly broadened and weakened Majorana zero bias peak, much
lower experimental temperatures are necessary for any definitive conclusion.
