ALMA [N ii] 205 m Imaging Spectroscopy of the Lensed Submillimeter Galaxy ID 141 at Redshift 4.24

We present an Atacama Large Millimeter/submillimeter Array observation of the Submillimeter galaxy ID 141 at z = 4.24 in the [N ii] 205 m line (hereafter [N ii] ) and the underlying continuum at (rest-frame) 197.6 m. Benefiting from lensing magnification by a galaxy pair at z = 0.595, ID 141 is one of the brightest SMGs. At the angular resolutions of -1 5 (1″ ∼6.9 kpc), our observation clearly separates and moderately resolves the two lensed images in both continuum and line emission at a signal-to-noise ratio >5. Our continuum-based lensing model implies an averaged amplification factor of ∼5.8 and reveals that the delensed continuum image has a Sérsic index and Sérsic radius of ∼0 18 (∼1.24 kpc). Furthermore, the reconstructed [N ii] velocity field in the source plane is dominated by a rotation component with a maximum velocity of ∼300 km s−1 at large radii, indicating a dark matter halo mass of ∼10 . This, together with the reconstructed velocity dispersion field being smooth and modest in value (