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The VANDELS Survey: New constraints on the high-mass X-ray binary populations in normal star-forming galaxies at 3 < z < 5.5

Saxena, A; Ellis, RS; Förster, PU; Calabrò, A; Pentericci, L; Carnall, AC; Castellano, M; ... Zamorani, G; + view all (2021) The VANDELS Survey: New constraints on the high-mass X-ray binary populations in normal star-forming galaxies at 3 < z < 5.5. Monthly Notices of the Royal Astronomical Society , 505 (4) pp. 4798-4812. 10.1093/mnras/stab1575. Green open access

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Abstract

We use VANDELS spectroscopic data overlapping with the ≃7 Ms Chandra Deep Field South survey to extend studies of high-mass X-ray binary systems (HMXBs) in 301 normal star-forming galaxies in the redshift range 3 < z < 5.5. Our analysis evaluates correlations between X-ray luminosities (LX), star formation rates (SFRs), and stellar metallicities (Z⋆) to higher redshifts and over a wider range in galaxy properties than hitherto. Using a stacking analysis performed in bins of both redshift and SFR for sources with robust spectroscopic redshifts without AGN signatures, we find convincing evolutionary trends in the ratio LX/SFR to the highest redshifts probed, with a stronger trend for galaxies with lower SFRs. Combining our data with published samples at lower redshift, the evolution of LX/SFR to z ≃ 5 proceeds as (1 + z)1.03 ± 0.02. Using stellar metallicities derived from photospheric absorption features in our spectroscopic data, we confirm indications at lower redshifts that LX/SFR is stronger for metal-poor galaxies. We use semi-analytic models to show that metallicity dependence of LX/SFR alone may not be sufficient to fully explain the observed redshift evolution of X-ray emission from HMXBs, particularly for galaxies with SFR < 30 M⊙ yr−1. We speculate that reduced overall stellar ages and ‘burstier’ star formation histories in the early Universe may lead to higher LX/SFR for the same metallicity. We then define the redshift-dependent contribution of HMXBs to the integrated X-ray luminosity density and, in comparison with models, find that the contribution of HMXBs to the cosmic X-ray background at z > 6 may be ≳0.25 dex higher than previously estimated.

Type: Article
Title: The VANDELS Survey: New constraints on the high-mass X-ray binary populations in normal star-forming galaxies at 3 < z < 5.5
Open access status: An open access version is available from UCL Discovery
DOI: 10.1093/mnras/stab1575
Publisher version: http://dx.doi.org/10.1093/mnras/stab1575
Language: English
Additional information: © The Author(s) 2021. Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
Keywords: Galaxies: evolution, galaxies: high-redshift, X-rays: binaries
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: https://discovery.ucl.ac.uk/id/eprint/10128657
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