D. Caruso
MCMC determination of the cosmic UV background at z ≃ 0 from Hα fluorescence
Caruso, D.; Haardt, F.; Fumagalli, M.; Cantalupo, S.
Authors
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 ΓHI ∼ 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 ΓHi=7.27+2.93−2.90×10−14 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.
Citation
Caruso, D., Haardt, F., Fumagalli, M., & Cantalupo, S. (2019). MCMC determination of the cosmic UV background at z ≃ 0 from Hα fluorescence. Monthly Notices of the Royal Astronomical Society, 482(2), 2833-2837. https://doi.org/10.1093/mnras/sty2956
Journal Article Type | Article |
---|---|
Acceptance Date | Oct 30, 2018 |
Online Publication Date | Nov 1, 2018 |
Publication Date | Jan 11, 2019 |
Deposit Date | Nov 21, 2018 |
Publicly Available Date | Nov 21, 2018 |
Journal | Monthly Notices of the Royal Astronomical Society |
Print ISSN | 0035-8711 |
Electronic ISSN | 1365-2966 |
Publisher | Royal Astronomical Society |
Peer Reviewed | Peer Reviewed |
Volume | 482 |
Issue | 2 |
Pages | 2833-2837 |
DOI | https://doi.org/10.1093/mnras/sty2956 |
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Copyright Statement
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2018 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
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