In a recent paper we reported on the detection of a diffuse H α glow in the outskirts of the nearby, edge-on disc galaxy UGC 7321 observed with the Multi-Unit Spectroscopic Explorer (MUSE) at the ESO Very Large Telescope. By interpreting the H α emission as fluorescence arising from hydrogen ionized by an external (i.e. extragalactic) radiation field, we estimated the UV background (UVB) intensity in terms of H I ionization rate (per ion) at z ≃ 0 to be in the range ΓH I ∼ 6 − 8 × 10−14 s−1. In the present work, by performing radiative transfer calculations over a large set of models of the gaseous disc of UGC 7321, we refine our estimate and through an MCMC analysis derive a value for the photoionization rate of ΓH i = 7.27+−229390 × 10−14 s−1. In particular, our analysis demonstrates that this value is robust against large variations in the galaxy model and that the uncertainties are mainly driven by the errors associated with the observed H α surface brightness. Our measurement is consistent with several recent determinations of the same quantity by a completely independent technique (i.e. flux decrement analysis of the Lyα forest), and support the notion that the low-redshift UVB is largely dominated by active galactic nuclei, possibly with no need of further contribution from star-forming galaxies

Caruso, D., Haardt, F., Fumagalli, M., Cantalupo, S. (2019). MCMC determination of the cosmic UV background at z ≃ 0 from H α fluorescence. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 482(2), 2833-2837 [10.1093/mnras/sty2956].

MCMC determination of the cosmic UV background at z ≃ 0 from H α fluorescence

Fumagalli M.;Cantalupo S.
2019

Abstract

In a recent paper we reported on the detection of a diffuse H α glow in the outskirts of the nearby, edge-on disc galaxy UGC 7321 observed with the Multi-Unit Spectroscopic Explorer (MUSE) at the ESO Very Large Telescope. By interpreting the H α emission as fluorescence arising from hydrogen ionized by an external (i.e. extragalactic) radiation field, we estimated the UV background (UVB) intensity in terms of H I ionization rate (per ion) at z ≃ 0 to be in the range ΓH I ∼ 6 − 8 × 10−14 s−1. In the present work, by performing radiative transfer calculations over a large set of models of the gaseous disc of UGC 7321, we refine our estimate and through an MCMC analysis derive a value for the photoionization rate of ΓH i = 7.27+−229390 × 10−14 s−1. In particular, our analysis demonstrates that this value is robust against large variations in the galaxy model and that the uncertainties are mainly driven by the errors associated with the observed H α surface brightness. Our measurement is consistent with several recent determinations of the same quantity by a completely independent technique (i.e. flux decrement analysis of the Lyα forest), and support the notion that the low-redshift UVB is largely dominated by active galactic nuclei, possibly with no need of further contribution from star-forming galaxies
Articolo in rivista - Articolo scientifico
Cosmology: theory; Intergalactic medium; Methods: numerical; Radiative transfer
English
2019
482
2
2833
2837
reserved
Caruso, D., Haardt, F., Fumagalli, M., Cantalupo, S. (2019). MCMC determination of the cosmic UV background at z ≃ 0 from H α fluorescence. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 482(2), 2833-2837 [10.1093/mnras/sty2956].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/258977
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