The origin and distribution of diffuse HI in the close interacting MHONGOOSE galaxy systems
Abstract
We present the deepest HI observations of the two systems with Dproj < 100 kpc, and Δ vsys < 200 km/s in the MHONGOOSE survey. The MeerKAT observations have a 3σ NHI = 1017.9 cm−2 over 16 km/s at 4 kpc scales. The new data detect HI in seven galaxies -- the interacting NGC 3511/3513 pair, and an interacting triplet (NGC 4781, NGC 4790 and UGCA 308) along with two new (2MASX J1255 and MKT 25413) dwarf satellites. Six galaxies lie on the star-forming main sequence, and their HI gas fractions are typical for such systems. In contrast, MKT 25413 has a log(MHI/Msun) = 5.7, which is the lowest MHI detected of a galaxy that is not a Milky Way satellite. This low surface brightness dwarf galaxy shows an anomalously low star formation and HI fraction for its stellar mass. We find ubiquitous low column density HI surrounding the galaxies, which is likely a consequence of mild tidal interactions from fly-bys in the past few hundred megayears. We derive the stellar and Hα kinematics from VLT/MUSE observations and the H2 kinematics from ALMA observations. The kinematics of the stellar and multiphase interstellar medium of the interacting galaxies display ordered rotation, and the atomic-to-molecular gas ratios are indistinguishable from star-forming field galaxies. The stellar morphology of all the interacting galaxies (except the low-mass dwarf UGCA 308) does not show major disruptions, and there is no stellar component associated with the HI tails, bridges or clouds in the intra-group mediums, down to μg = 29 mag arcsec−2. We surmise that the mild environmental interactions in the close systems are able to pull the diffuse HI out of the disk and redistribute it. The gas is not in equilibrium, although it remains bound and is in the process of falling back onto the disk.
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BibTeX
@misc{kleiner2026origin,
title = {{The origin and distribution of diffuse HI in the close interacting MHONGOOSE galaxy systems}},
author = {D. Kleiner and W. J. G. de Blok and J. Healy and F. M. Maccagni and E. M. Di Teodoro and A. Fraser-McKelvie and A. Marasco and S. Veronese and S. Kurapati},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.34366},
eprint = {2610.34366},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.34366},
}
RIS
TY - UNPB
TI - The origin and distribution of diffuse HI in the close interacting MHONGOOSE galaxy systems
AU - D. Kleiner
AU - W. J. G. de Blok
AU - J. Healy
AU - F. M. Maccagni
AU - E. M. Di Teodoro
AU - A. Fraser-McKelvie
AU - A. Marasco
AU - S. Veronese
AU - S. Kurapati
PY - 2026
DA - 2026/10/25
PB - arXiv
DO - 10.48550/arxiv.2610.34366
UR - https://arxiv.org/abs/2610.34366
AB - We present the deepest HI observations of the two systems with Dproj < 100 kpc, and Δ vsys < 200 km/s in the MHONGOOSE survey. The MeerKAT observations have a 3σ NHI = 10^17.9 cm^−2 over 16 km/s at 4 kpc scales. The new data detect HI in seven galaxies -- the interacting NGC 3511/3513 pair, and an interacting triplet (NGC 4781, NGC 4790 and UGCA 308) along with two new (2MASX J1255 and MKT 25413) dwarf satellites. Six galaxies lie on the star-forming main sequence, and their HI gas fractions are typical for such systems. In contrast, MKT 25413 has a log(MHI/Msun) = 5.7, which is the lowest MHI detected of a galaxy that is not a Milky Way satellite. This low surface brightness dwarf galaxy shows an anomalously low star formation and HI fraction for its stellar mass. We find ubiquitous low column density HI surrounding the galaxies, which is likely a consequence of mild tidal interactions from fly-bys in the past few hundred megayears. We derive the stellar and Hα kinematics from VLT/MUSE observations and the H2 kinematics from ALMA observations. The kinematics of the stellar and multiphase interstellar medium of the interacting galaxies display ordered rotation, and the atomic-to-molecular gas ratios are indistinguishable from star-forming field galaxies. The stellar morphology of all the interacting galaxies (except the low-mass dwarf UGCA 308) does not show major disruptions, and there is no stellar component associated with the HI tails, bridges or clouds in the intra-group mediums, down to μ_g = 29 mag arcsec^−2. We surmise that the mild environmental interactions in the close systems are able to pull the diffuse HI out of the disk and redistribute it. The gas is not in equilibrium, although it remains bound and is in the process of falling back onto the disk.
ER -