The MeerKAT Fornax Survey. III. Ram-pressure stripping of the tidally interacting galaxy NGC 1427A in the Fornax cluster

Serra, P., Oosterloo, T., Kamphuis, P., Jozsa, G.I.G., de Blok, W.J.G., Bryan, G.L., van Gorkom, J.H., Iodice, E., Kleiner, D., Loni, A., Loubser, S.I., Maccagni, F.M., Molnar, D., Peletier, R., Pisano, D.J., Ramatsoku, M., Smith, M.W.L. ORCID: https://orcid.org/0000-0002-3532-6970, Verheijen, M.A.W. and Zabel, N. 2024. The MeerKAT Fornax Survey. III. Ram-pressure stripping of the tidally interacting galaxy NGC 1427A in the Fornax cluster. Astronomy & Astrophysics 690 , A4. 10.1051/0004-6361/202450114

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Abstract

We present MeerKAT Fornax Survey H I observations of NGC 1427A, a blue irregular galaxy with a stellar mass of ∼2 × 109 M⊙ located near the centre of the Fornax galaxy cluster. Thanks to the excellent resolution (1–6 kpc spatially, 1.4 km s−1 in velocity) and H I column density sensitivity (∼4 × 1019 to ∼1018 cm−2 depending on resolution), our data deliver new insights on the long-debated interaction of this galaxy with the cluster environment. We confirm the presence of a broad, one-sided, starless H I tail stretching from the outer regions of the stellar body and pointing away from the cluster centre. We find the tail to have 50% more H I (4 × 108 M⊙) and to be 3 times longer (70 kpc) than in previous observations. In fact, we detect scattered H I clouds out to 300 kpc from the galaxy in the direction of the tail – possibly the most ancient remnant of the passage of NGC 1427A through the intracluster medium of Fornax. Both the velocity gradient along the H I tail and the peculiar kinematics of H I in the outer region of the stellar body are consistent with the effect of ram pressure given the line-of-sight motion of the galaxy within the cluster. However, several properties cannot be explained solely by ram pressure and suggest an ongoing tidal interaction. This includes: the close match between dense H I and stars within the disturbed stellar body; the abundant kinematically anomalous H I; and the inversion of the H I velocity gradient near the base of the H I tail. We rule out an interaction with the cluster tidal field, and conclude that NGC 1427A is the result of a high-speed galaxy encounter or of a merger started at least 300 Myr ago, where ram pressure shapes the distribution and kinematics of the H I in the perturbed outer stellar body and in the tidal tails.

Item Type:	Article
Date Type:	Published Online
Status:	Published
Schools:	Physics and Astronomy
Publisher:	EDP Sciences
ISSN:	0004-6361
Funders:	STFC
Date of First Compliant Deposit:	30 September 2024
Last Modified:	30 Sep 2024 11:15
URI:	https://orca.cardiff.ac.uk/id/eprint/171871

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