A MeerKAT view of pre-processing in the Fornax A group

KLEINER, DANEDANEKLEINERSERRA, PaoloPaoloSERRAMACCAGNI, Filippo MarcelloFilippo MarcelloMACCAGNIVenhola, A.A.VenholaMorokuma-Matsui, K.K.Morokuma-MatsuiPeletier, R.R.PeletierIODICE, ENRICHETTAENRICHETTAIODICERAJ, Maria AngelaMaria AngelaRAJde Blok, W.J.G.W.J.G.de BlokComrie, A.A.ComrieJózsa, G.I.G.G.I.G.JózsaKamphuis, P.P.KamphuisLoni, A.A.LoniLoubser, S.I.S.I.LoubserMolnár, D. Cs.D. Cs.MolnárPassmoor, S. S.S. S.PassmoorRAMATSOKU, MPATI ANALICIAMPATI ANALICIARAMATSOKUSivitilli, A.A.SivitilliSmirnov, O.O.SmirnovThorat, K.K.ThoratVITELLO, Fabio RobertoFabio RobertoVITELLO2025-02-252025-02-2520210004-6361http://hdl.handle.net/20.500.12386/36220We present MeerKAT neutral hydrogen (H I) observations of the Fornax A group, which is likely falling into the Fornax cluster for the first time. Our H I image is sensitive to 1.4 × 1019 atoms cm−2 over 44.1 km s−1, where we detect H I in 10 galaxies and a total of (1.12 ± 0.02) × 109 M⊙ of H I in the intra-group medium (IGM). We search for signs of pre-processing in the 12 group galaxies with confirmed optical redshifts that reside within the sensitivity limit of our H I image. There are 9 galaxies that show evidence of pre-processing and we classify each galaxy into their respective pre-processing category, according to their H I morphology and gas (atomic and molecular) scaling relations. Galaxies that have not yet experienced pre-processing have extended H I discs and a high H I content with a H2-to-H I ratio that is an order of magnitude lower than the median for their stellar mass. Galaxies that are currently being pre-processed display H I tails, truncated H I discs with typical gas fractions, and H2-to-H I ratios. Galaxies in the advanced stages of pre-processing are the most H I deficient. If there is any H I, they have lost their outer H I disc and efficiently converted their H I to H2, resulting in H2-to-H I ratios that are an order of magnitude higher than the median for their stellar mass. The central, massive galaxy in our group (NGC 1316) underwent a 10:1 merger ∼2 Gyr ago and ejected 6.6−11.2 × 108 M⊙ of H I, which we detect as clouds and streams in the IGM, some of which form coherent structures up to ∼220 kpc in length. We also detect giant (∼100 kpc) ionised hydrogen (Hα) filaments in the IGM, likely from cool gas being removed (and subsequently ionised) from an in-falling satellite. The Hα filaments are situated within the hot halo of NGC 1316 and there are localised regions that contain H I. We speculate that the Hα and multiphase gas is supported by magnetic pressure (possibly assisted by the NGC 1316 AGN), such that the hot gas can condense and form H I that survives in the hot halo for cosmological timescales.STAMPAenA MeerKAT view of pre-processing in the Fornax A groupArticle10.1051/0004-6361/2020398982-s2.0-85103916683WOS:000639797700001https://publons.com/wos-op/publon/44399280/https://www.aanda.org/articles/aa/full_html/2021/04/aa39898-20/aa39898-20.html2021A&A...648A..32KFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation