MeerKAT-64 discovers wide-spread tidal debris in the nearby NGC 7232 galaxy group

• Published in: Monthly notices of the Royal Astronomical Society Vol. 505; no. 3; pp. 3795 - 3809
• Main Authors: Namumba, B, Koribalski, B S, Józsa, G I G, Lee-Waddell, K, Jones, M G, Carignan, C, Verdes-Montenegro, L, Ianjamasimanana, R, de Blok, W J G, Cluver, M, Garrido, J, Sánchez-Expósito, S, Ramaila, A J T, Thorat, K, Andati, L A L, Hugo, B V, Kleiner, D, Kamphuis, P, Serra, P, Smirnov, O M, Maccagni, F M, Makhathini, S, Molnár, D Cs, Perkins, S, Ramatsoku, M, White, S V, Loi, F
• Format: Journal Article
• Language: English
• Published: Oxford University Press 01-08-2021
• Subjects: galaxies: groups: individual: NGC 7232; radio lines: galaxies; intergalactic medium; galaxies: interactions; techniques: interferometric
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stab1524

ABSTRACT
We report the discovery of large amounts of previously undetected cold neutral atomic hydrogen (H i) around the core triplet galaxies in the nearby NGC 7232 galaxy group with MeerKAT. With a physical resolution of ∼1 kpc, we detect a complex web of low-surface-brightness H i emission down to a 4σ column density level of ∼1 × 1019 cm−2 (over 44  km s−1). The newly discovered H i streams extend over ∼20 arcmin corresponding to 140 kpc in projection. This is approximately three times the H i extent of the galaxy triplet (52 kpc). The H i debris has an H i mass of ∼6.6 × 109 M⊙, more than 50 per cent of the total H i mass of the triplet. Within the galaxy triplet, NGC 7233 and NGC 7232 have lost a significant amount of H i while NGC 7232B appears to have an excess of H i. The H i deficiency in NGC 7232 and NGC 7233 indicates that galaxy–galaxy interaction in the group concentrates on this galaxy pair while the other disc galaxies have visited them over time. In comparison to the AMIGA sample of isolated galaxies, we find that with regards to its total H i mass the NGC 7232/3 galaxy triplet is not H i-deficient. Despite the many interactions associated to the triplet galaxies, no H i seems to have been lost from the group (yet).