Browsing by Author "Belfiore, F."

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    Gas, dust, and the CO-to-molecular gas conversion factor in low-metallicity starbursts⋆
    (2023) Hunt, L. K.; Belfiore, F.; Lelli, F.; Draine, B. T.; Marasco, A.; Garcia-Burillo, S.; Venturi, G.; Combes, F.; Weiss, A.; Henkel, C.; Menten, K. M.; Annibali, F.; Casasola, V.; Cignoni, M.; McLeod, A.; Tosi, M.; Beltran, M.; Concas, A.; Cresci, G.; Ginolfi, M.; Kumari, N.; Mannucci, F.
    The factor relating CO emission to molecular hydrogen column density, X-CO, is still subject to uncertainty, in particular at low metallicity. In this paper, to quantify X-CO at two different spatial resolutions, we exploited a dust-based method together with ALMA 12-m and ACA data and H I maps of three nearby metal-poor starbursts, NGC 625, NGC 1705, and NGC 5253. Dust opacity at 250 pc resolution was derived based on dust temperatures estimated by fitting two-temperature modified blackbodies to Herschel PACS data. By using the HI maps, we were then able to estimate dust-to-gas ratios in the regions dominated by atomic gas, and, throughout the galaxy, to infer total gas column densities and H-2 column densities as the difference with HI. Finally, from the ACA CO(1-0) maps, we derived X-CO. We used a similar technique with 40 pc ALMA 12-m data for the three galaxies, but instead derived dust attenuation at 40 pc resolution from reddening maps based on VLT/MUSE data. At 250 pc resolution, we find X-CO  & SIM; 10(22) - 10(23) cm(-2)/K km s(-1), 5-1000 times the Milky Way value, with much larger values than would be expected from a simple metallicity dependence. Instead, at 40 pc resolution, X-CO again shows large variation, but is roughly consistent with a power-law metallicity dependence, given the Z  & SIM; 1/3 Z(& ODOT;) metal abundances of our targets. The large scatter in both estimations could imply additional parameter dependence, which we have investigated by comparing X-CO with the observed velocity-integrated brightness temperatures, I-CO, as predicted by recent simulations. Indeed, larger X-CO is significantly correlated with smaller I-CO, but with slightly different slopes and normalizations than predicted by theory. Such behavior can be attributed to the increasing fraction of CO-faint (or dark) H-2 gas with lower spatial resolution (larger beams). This confirms the idea the X-CO is multivariate, depending not only on metallicity but also on the CO brightness temperature and beam size. Future work is needed to consolidate these empirical results by sampling galaxies with different metal abundances observed at varying spatial resolutions.
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    Properties of the multiphase outflows in local (ultra)luminous infrared galaxies
    (2021) Fluetsch, A.; Maiolino, R.; Carniani, S.; Arribas, S.; Belfiore, F.; Bellocchi, E.; Cazzoli, S.; Cicone, C.; Cresci, G.; Fabian, A. C.; Gallagher, R.; Ishibashi, W.; Mannucci, F.; Marconi, A.; Perna, M.; Sturm, E.; Venturi, G.
    Galactic outflows are known to consist of several gas phases; however, the connection between these phases has been investigated little and only in a few objects. In this paper, we analyseMulti Unit Spectroscopic Explorer (MUSE)/Very Large Telescope (VLT) data of 26 local (U)LIRGs and study their ionized and neutral atomic phases. We also include objects from the literature to obtain a sample of 31 galaxies with spatially resolved multiphase outflow information. We find that the ionized phase of the outflows has on average an electron density three times higher than the disc (n(e,disc) similar to 145 cm(-3) versus n(e,outflow) similar to 500 cm(-3)), suggesting that cloud compression in the outflow is more important than cloud dissipation. We find that the difference in extinction between outflow and disc correlates with the outflow gas mass. Together with the analysis of the outflow velocities, this suggests that at least some of the outflows are associated with the ejection of dusty clouds from the disc. This may support models where radiation pressure on dust contributes to driving galactic outflows. The presence of dust in outflows is relevant for potential formation of molecules inside them. We combine our data with millimetre data to investigate the molecular phase. We find that the molecular phase accounts for more than 60 per cent of the total mass outflow rate in most objects and this fraction is higher in active galactic nuclei (AGN)-dominated systems. The neutral atomic phase contributes of the order of 10 per cent, while the ionized phase is negligible. The ionized-to-molecular mass outflow rate declines slightly with AGN luminosity, although with a large scatter.
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    SDSS-IV MaNGA : inside-out versus outside-in quenching of galaxies in different local environments
    (2019) Lin, L.W.; Hsieh, B.C.; Pa, H.A.; Rembold, A.B.; Sanchez, S.F.; Argudo Fernandez, M.; Rowlands, K.; Belfiore, F.; Bizyael, D.; Rong, Y.