A MeerKAT View of the Neutral Atomic Gas in Stephan's Quintet
May 2026 • 2026ApJ..1002...18R
Abstract • We present new MeerKAT 21 cm line observations of the neutral hydrogen gas in the compact galaxy group Stephan's Quintet. These data provide a significantly improved view of the atomic gas distribution and kinematics in the group. New features include the first detections of H I associated with member galaxies NGC 7319 and NGC 7320C, the identification of a high-velocity H I component associated with SQ-A, and the detection of additional H I at low velocities filling the area of the NGC 7318B disk. We also find H I in the previously detected gas bridge linking NGC 7319 and NGC 7318B, and a new northern bridge linking NGC 7319 to the SQ-A star formation region. We detect H I with a wide range of velocities along the line of sight through the northern half of the famous shock ridge, including in the 6200─6500 km s−1 velocity range occupied by shocked Hα emission. We examine the morphology and velocity structure of the H I and consider the origins of different components, finding some evidence that while the gas associated with NGC 7318B has been disturbed by its collision with the group, it may still retain a component of disk rotation. We find no gaseous connection between the tidal tails and NGC 7320C, but reaffirm the close connection between the shocked gas in the ridge (traced by X-ray, radio continuum, and warm H2 emission) and the southern tidal tail. Based on the integrated spectrum, we find a total H I mass in the group of 3.5 ± 0.4 × 1010 M⊙, higher than the Very Large Array estimate and comparable to FAST.
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