A Nascent Tidal Dwarf Galaxy Forming within the Northern HI Streamer of
  M82
  We identify a $\sim$600 pc-wide region of active star formation located
within a tidal streamer of M82 via $H\alpha$ emission ($F_{H\alpha}\sim
6.5\times10^{-14}$ erg s$^{-1}$ cm$^{-2}$), using a pathfinder instrument based
on the Dragonfly Telephoto Array. The object is kinematically decoupled from
the disk of M82 as confirmed via Keck / LRIS spectroscopy, and is spatially and
kinematically coincident with an overdensity of HI and molecular hydrogen
within the "northern HI streamer" induced by the passage of M81 several hundred
Myr ago. From HI data, we estimate that $\sim5\times10^7$ M$_{\odot}$ of gas is
present in the specific overdensity coincident with the $H\alpha$ source. The
object's derived metallicity (12+$\log(O/H)\simeq 8.6$), position within a
gas-rich tidal feature, and morphology (600 pc diameter with multiple star
forming clumps), indicate that it is likely a tidal dwarf galaxy in the
earliest stages of formation.
