Examinando por Autor "Maccagni F.M."
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Ítem 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.Ítem 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.Ítem Searching for HI around MHONGOOSE galaxies via spectral stacking(Astronomy and Astrophysics, Volume 6931 January 2025 Article number A97, 2025) Veronese S.; de Blok W.J.G.; Healy J.; Kleiner D.; Marasco A.; Maccagni F.M.; Kamphuis P.; Brinks E.; Holwerda B.W.; Zabel N.; Chemin L.; Adams E.A.K.; Kurapati S.; Sorgho A.; Spekkens K.; Combes F.; Pisano D.J.; Walter F.; Amram P.; Bigiel F.; Wong O.I.; Athanassoula E.The observed star formation rates of galaxies in the Local Universe suggests that they are replenishing their gas reservoir across cosmic time. Cosmological simulations predict that this accretion of fresh gas can occur in a hot or a cold mode, yet the existence of low column density (∼1017 cm−2) neutral atomic hydrogen (Hi) tracing the cold mode has not been unambiguously confirmed by observations. We present the application of unconstrained spectral stacking to attempt to detect the emission from this Hi in the circumgalactic medium (CGM) and intergalactic medium (IGM) of six nearby star-forming galaxies from the MHONGOOSE sample for which full-depth observations are available. Our stacking procedure consists of a standard spectral stacking algorithm coupled with a one-dimensional spectral line finder designed to extract a reliable signal close to the noise level. In agreement with previous studies, we find that the amount of signal detected outside the Hi disk is much smaller than implied by simulations. Furthermore, the column density limit that we achieve via stacking (∼1017 cm−2) suggests that direct detection of the neutral CGM and IGM component might be challenging in the future, even with the next generation of radio telescopes. © The Authors 2025