New Surface Brightness Fluctuations Spectroscopic Technique: NGC4449 and
  its Stellar Tidal Stream
  We present a new spectroscopic technique based in part on targeting the
upward fluctuations of the surface brightness for studying the internal stellar
kinematics and metallicities of low surface brightness galaxies and streams
beyond the Local Group. The distance to these systems makes them unsuitable for
targeting individual red giant branch (RGB) stars (tip of RGB at
$I\gtrsim24$~mag) and their surface brightness is too low ($\mu_r\gtrsim
25$~mag~arcsec$^{-2}$) for integrated light spectroscopic measurements. This
technique overcomes these two problems by targeting individual objects that are
brighter than the tip of the RGB. We apply this technique to the star-forming
dwarf galaxy NGC 4449 and its stellar stream. We use Keck/DEIMOS data to
measure the line-of-sight radial velocity out to $\sim7$~kpc in the East side
of the galaxy and $\sim8$~kpc along the stream. We find that the two systems
are likely gravitationally bound to each other and have heliocentric radial
velocities of $227.3\pm10.7$~km/s and $225.8\pm16.0$~km/s, respectively.
Neither the stream nor the near half of the galaxy shows a significant velocity
gradient. We estimate the stellar metallicity of the stream based on the
equivalent width of its Calcium triplet lines and find [Fe/H]~$=-1.37\pm0.41$,
which is consistent with the metallicity-luminosity relation for Local Group
dwarf galaxies. Whether the stream's progenitor was moderately or severely
stripped cannot be constrained with this metallicity uncertainty. We
demonstrate that this new technique can be used to measure the kinematics and
(possibly) the metallicity of the numerous faint satellites and stellar streams
in the halos of nearby ($\sim 4$~Mpc) galaxies.
