Tidal pre-conditioning and ram-pressure stripping in NGC 1427A. Deep VLT/MUSE spectroscopy and FUV-to-radio observations trace a Fornax Cluster dwarf in transformation

J. P. Carvajal; T. H. Puzia; M. Blaña; P. K. Nayak; K. Fahrion; M. Hilker; E. Emsellem; E. D. Skillman; M. D. Mora; B. Miller; Y. Ordenes-Briceño; P. Eigenthaler; R. Rahatgaonkar; J. Chanamé

arXiv · 2605.00988

Tidal pre-conditioning and ram-pressure stripping in NGC 1427A. Deep VLT/MUSE spectroscopy and FUV-to-radio observations trace a Fornax Cluster dwarf in transformation

J. P. Carvajal·T. H. Puzia·M. Blaña·P. K. Nayak·K. Fahrion·M. Hilker·E. Emsellem·E. D. Skillman·M. D. Mora·B. Miller·Y. Ordenes-Briceño·P. Eigenthaler·R. Rahatgaonkar·J. Chanamé

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Abstract

The early environmental transformation of low-mass cluster galaxies from gas-rich to gas-poor remains poorly constrained, partly because clear, phase-resolved observations are rare. NGC 1427A, a disturbed star-forming dwarf in the Fornax cluster, offers a favorable case for studying this process. We aim to build a spatially resolved, multi-phase picture of NGC 1427A to constrain the roles of ram-pressure stripping and tidal perturbations. We combine a deep, spatially contiguous VLT/MUSE mosaic with ancillary data from the FUV to the radio. Full-spectrum fitting of the MUSE cube yields maps of stellar kinematics, ages, metallicities, and continuum attenuation, while emission-line modeling provides ionized-gas kinematics, Balmer-decrement reddening, and star-formation-rate surface densities. Ancillary multi-wavelength data trace neutral and molecular gas, dust, and recent star formation, placing the MUSE-based results in a broader multi-phase context. We find a pronounced decoupling between stars and gas: the H I and ionized gas rotate about an axis tilted with respect to the stellar field and are globally blueshifted. Stellar and nebular attenuation, infrared dust tracers, and H I morphology indicate stripping with a strong line-of-sight component that has reached the ISM. At the same time, the asymmetric gas and dust distribution, together with structured and time-dependent star formation, points to an additional gravitational perturbation, with a recent mild fly-by by a nearby dwarf being the favored interpretation. We propose that dwarf-dwarf tidal effects have torqued and pre-conditioned the gas, while the Fornax intracluster medium is driving ram-pressure stripping that now reaches the ISM and coincides with a declining global star formation rate. This places NGC 1427A at the onset of environmental quenching, making it a useful benchmark for early cluster dwarf transformation.

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J. P. Carvajal, T. H. Puzia, M. Blaña, P. K. Nayak, K. Fahrion, M. Hilker, E. Emsellem, E. D. Skillman, M. D. Mora, B. Miller, Y. Ordenes-Briceño, P. Eigenthaler, R. Rahatgaonkar, J. Chanamé. 2026-05-01. Tidal pre-conditioning and ram-pressure stripping in NGC 1427A. Deep VLT/MUSE spectroscopy and FUV-to-radio observations trace a Fornax Cluster dwarf in transformation. https://arxiv.org/abs/2605.00988

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