Abstract
Abstract We identify a ∼600 pc wide region of active star formation located within a tidal streamer of M82 via Hα emission (F Hα ∼ 6.5 × 10−14 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 H i and molecular hydrogen within the “northern H i streamer” induced by the passage of M81 several hundred Myr ago. From H i data, we estimate that ∼5 × 107 M ⊙ of gas is present in the specific overdensity coincident with the Hα source. The object’s derived metallicity (12+ log ( O / H ) ≃ 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.
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