A census of H$\alpha$ emitters in the intergalactic medium of the NGC
  2865 system
  Tidal debris which are rich in HI gas, formed in interacting and merging
systems, are suitable laboratories to study star formation outside galaxies.
Recently, several such systems were observed, which contained many young star
forming regions outside the galaxies. In previous works, we have studied young
star forming regions outside galaxies in different systems with optical and/or
gaseous tidal debris, all of them with available archive GALEX/UV images, in
order to understand how often they occur and in which type of environments. In
this paper we searched for star forming regions around the galaxy NGC2865, a
shell galaxy which is circled by a ring of HI, with a total mass of 1.2 x
10$^9$ M$_\odot$. Using the Multi-Slit Imaging Spectroscopy Technique with the
Gemini telescope, we detected all H$\alpha$ emitting sources in the
surroundings of the galaxy NGC2865, down to a flux limit of 10$^{-18}$ erg
cm$^{-2}$ s$^{-1}$ \AA$^{-1}$. Together with Near and Far-Ultraviolet flux
information we characterize the star formation rates, masses, ages, and
metallicities for these HII regions. In total, we found 26 emission-line
sources in a 60 $\times$ 60 Kpc field centered over the southeastern tail of
the HI gas present around the galaxy NGC2865. Out of the 26 H$\alpha$ emitters,
19 are in the satellite galaxy FGCE 0745 and seven are intergalactic HII
regions scattered over the south tail of the HI gas around NGC2865. We found
that the intergalactic HII regions are young ($<$200 Myr) with stellar masses
in the range 4 X 10$^3$M$_\odot$ to 17x10$^6$ M$_\odot$. These are found in a
region of low HI gas density, where the probability of forming stars is
expected to be low. For one of the intergalactic HII regions we estimated a
solar oxygen abundance of 12 + log(O/H) $\sim$ 8.7. We also were able to
estimate the metallicity for the satellite galaxy FGCE0745 to be 12 + log(O/H)
~ 8.0.
