A feather on the hat: Tracing the giant stellar stream around the
  Sombrero galaxy
  Recent evidence of extremely metal-rich stars found in the Sombrero galaxy
(M104) halo suggests that this galaxy has undergone a recent major merger with
a relatively massive galaxy. In this paper, we present wide-field deep images
of the M104 outskirts obtained with a 18-cm amateur telescope with the purpose
of detecting any coherent tidal features from this possible major merger. Our
new data, together with a model of the M104 inner halo and scattered light from
stars around the field, allow us to trace for the first time the full path of
the stream on both sides of the disk of the galaxy. We fully characterize the
ring-like tidal structure and we confirm that this is the only observable
coherent substructure in the inner halo region. This result is in agreement
with the hypothesis that M104 was created by a wet major merger more than 3.5
Gyr ago that heated up the stellar population, blurring all old substructure.
We generated a set of numerical models that reproduce the formation of the
observed tidal structure. Our best fit model suggests the formation of this
stream in the last 3 Gyr is independent of the wet major merger that created
the M104 system. Therefore, the formation of the tidal stream can put a
constraint on the time when the major merger occurred.
