Letter to the Editor

Origin of gas in the Magellanic Bridge: MeerKAT detection of H I 21 cm absorption

¹ Argelander-Institut für Astronomie, Auf dem Hügel 71, D-53121 Bonn, Germany
² Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune 411 007, India
³ Institut d’astrophysique de Paris, UMR 7095, CNRS, 98bis bd Arago, 75014 Paris, France
⁴ Ioffe Institute, 26 Politeknicheskaya st., St. Petersburg 194021, Russia
⁵ Departement of Astronomy and Astrophysics, The University of Chicago, Chicago, IL 60637, USA
⁶ Observatoire de Paris, Collège de France, PSL University, Sorbonne University, CNRS, LUX, Paris, France
⁷ National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA
⁸ National Radio Astronomy Observatory, 1011 Lopezville Road, Socorro, NM 87801, USA

^⋆ Corresponding author: jkerp@uni-bonn.de

Received: 2 April 2025
Accepted: 23 September 2025

Abstract

Aims. H I 21 cm absorption lines are investigated to determine the origin of the neutral atomic hydrogen (H I) of the Magellanic Bridge (MB). Using MeerKat Absorption Line Survey (MALS) data, we report the detection of an H I absorption line at a peak signal-to-noise ratio (S/N) of 10 caused by MB gas observed against the radio source J033242.97-724904.5. In combination with earlier data obtained with the Australia Telescope Compact Array (ATCA), our new detected H I line enables the exploration of the MB atomic hydrogen gas across 4–6 kpc.

Methods. We investigated the radial velocity profiles from the ATCA data and included new data from MALS in the analysis. Apart from the excitation conditions, we considered the radial velocity structure of the H I gas seen in emission and absorption. The gas-to-dust ratio was quantified to help identify whether the MB gas had originated from the SMC (Small Magellanic Cloud) or the LMC (Large Magellanic Cloud).

Results. The H I absorption lines toward lines of sight separated by a few kiloparsecs consistently coincide with the densest and possibly the coolest gas at the lower radial-velocity limit of the corresponding H I emission profiles. The gas-to-dust ratio was found to be consistent with the MB gas originating in the LMC. The large-scale velocity distribution, as seen from the H I absorption features, favors the LMC-SMC direct collision scenario over the close fly-by scenario, which is also supported by results from recent numerical simulations.