A MeerKAT view of the Neutral Atomic Gas in Stephan's Quintet

TL;DR

This paper presents new MeerKAT 21cm observations revealing detailed neutral hydrogen distribution and kinematics in Stephan's Quintet, including new detections and insights into gas dynamics and interactions.

Contribution

First detailed MeerKAT HI observations of Stephan's Quintet, identifying new features and providing improved understanding of gas distribution and motion in the group.

Findings

Detected HI in member galaxies NGC 7319 and NGC 7320C for the first time.

Identified an additional high-velocity HI component in SQ-A.

Measured a total HI mass of approximately 3.5×10^{10} solar masses.

Abstract

We present new MeerKAT 21cm spectral line observations of the neutral hydrogen gas in the compact galaxy group Stephan's Quintet (HCG 92). These data provide a significantly improved view of the atomic gas distribution and kinematics in the group. New features include the first detections of HI associated with member galaxies NGC 7319 and NGC 7320C, the identification of an additional high-velocity HI component associated with SQ-A, and the detection of additional HI at low velocities filling much of the area of the NGC~7318B disk. We also find HI 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 HI 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$\rm\,km\,s^{-1}$ velocity range occupied by shocked H$\alpha$ emission. We examine the morphology and velocity structure of the HI 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 H$_2$ emission) and the southern tidal tail. Based on the integrated spectrum, we find a total HI mass in the group of 3.5$\pm$0.4$\times$10$^{10}\,M_{\odot}$, higher than the VLA estimate and comparable to FAST.