Examinando por Autor "Maccagni F.M."

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    MHONGOOSE discovery of a gas-rich low surface brightness galaxy in the Dorado group
    (EDP Sciences, 2024-10) Maccagni F.M.; De Blok W.J.G.; Mancera Piña P.E.; Ragusa R.; Iodice E.; Spavone M.; Mcgaugh S.; Oman K.A.; Oosterloo T.A.; Koribalski B.S.; Kim M.; Adams E.A.K.; Amram P.; Bosma A.; Bigiel F.; Brinks E.; Chemin L.; Combes F.; Gibson B.; Healy J.; Holwerda B.W.; Józsa G.I.G.; Kamphuis P.; Kleiner D.; Kurapati S.; Marasco A.; Spekkens K.; Veronese S.; Walter F.; Zabel N.; Zijlstra A.
    We present the discovery of a low-mass, gas-rich low surface brightness galaxy in the Dorado group, at a distance of 17.7 Mpc. Combining deep MeerKAT 21-cm observations from the MeerKAT Hi Observations of Nearby Galactic Objects: Observing Southern Emitters (MHONGOOSE) survey with deep photometric images from the VST Early-type Galaxy Survey (VEGAS) we find a stellar and neutral atomic hydrogen (H i) gas mass of M∗ = 2:23 × 106M⊙ and MHI = 1:68 × 106 M⊙, respectively. This low surface brightness galaxy is the lowest-mass Hi detection found in a group beyond the local Universe (D ≳ 10 Mpc). The dwarf galaxy has the typical overall properties of gas-rich low surface brightness galaxies in the Local group, but with some striking differences. Namely, the MHONGOOSE observations reveal a very low column density (∼ 1018-19 cm-2) Hi disk with asymmetrical morphology possibly supported by rotation and higher velocity dispersion in the centre. There, deep optical photometry and UV observations suggest a recent enhancement of the star formation. Found at galactocentric distances where in the Local Group dwarf galaxies are depleted of cold gas (at a projected distance of 390 kpc from the group centre), this galaxy is likely on its first orbit within the Dorado group. We discuss the possible environmental effects that may have caused the formation of the Hi disk and the enhancement of star formation (SF), highlighting the short-lived phase (a few hundreds million years) of the gaseous disk, before either SF or hydrodynamical forces will deplete the gas of the galaxy.
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    Possible origins of anomalous Ha I gas around MHONGOOSE galaxy, NGC 5068
    (EDP Sciences, 2024-07) Healy J.; De Blok W.J.G.; Maccagni F.M.; Amram P.; Chemin L.; Combes F.; Holwerda B.W.; Kamphuis P.; Pisano D.J.; Schinnerer E.; Spekkens K.; Verdes-Montenegro L.
    The existing reservoirs of neutral atomic hydrogen gas (HI) in galaxies are insufficient to have maintained the observed levels of star formation without some kind of replenishment. This refuelling of the H I reservoirs is likely to occur at column densities an order of magnitude lower than previous observational limits (NHI, limit ∼ 1019 cm-2 at a 30″ resolution over a linewidth of 20 km s-1). In this paper, we present recent deep HI observations of NGC 5068, a nearby isolated star-forming galaxy observed by MeerKAT as part of the MHONGOOSE survey. With these new data, we were able to detect low column density HI around NGC 5068 with a 3σ detection limit of NHI = 6.4 × 1017 cm-2 at a 90″ resolution over a 20 km s-1 linewidth. The high sensitivity and resolution of the MeerKAT data reveal a complex morphology of the HI in this galaxy, a regularly rotating inner disk coincident with the main star-forming disk of the galaxy, a warped outer disk of low column density gas (NHI < 9 × 1019 cm-2), in addition to clumps of gas on the north-western side of the galaxy. We employed a simple two disk model that described the inner and outer disks, which enabled us to identify anomalous gas that deviates from the rotation of the main galaxy. The morphology and the kinematics of the anomalous gas suggest a possible extra-galactic origin. We explore a number of possible origin scenarios that may explain the anomalous gas, and conclude that fresh accretion is the most likely scenario.