SAXENA, AAYUSHAAYUSHSAXENAEllis, R. S.R. S.EllisFörster, P. U.P. U.FörsterCalabrò, A.A.CalabròPENTERICCI, LauraLauraPENTERICCICarnall, A. C.A. C.CarnallCASTELLANO, MARCOMARCOCASTELLANOCullen, F.F.CullenFONTANA, AdrianoAdrianoFONTANAFranco, M.M.FrancoFynbo, J. P. U.J. P. U.FynboGARGIULO, ADRIANAADRIANAGARGIULOGARILLI, BIANCA MARIA ROSABIANCA MARIA ROSAGARILLIHathi, N. P.N. P.HathiMcLeod, D. J.D. J.McLeodAmorín, R.R.AmorínZamorani, G.G.Zamorani2022-06-082022-06-0820210035-8711http://hdl.handle.net/20.500.12386/32243We 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 (L<SUB>X</SUB>), star formation rates (SFRs), and stellar metallicities (Z<SUB>⋆</SUB>) 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 L<SUB>X</SUB>/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 L<SUB>X</SUB>/SFR to z ≃ 5 proceeds as (1 + z)<SUP>1.03 ± 0.02</SUP>. Using stellar metallicities derived from photospheric absorption features in our spectroscopic data, we confirm indications at lower redshifts that L<SUB>X</SUB>/SFR is stronger for metal-poor galaxies. We use semi-analytic models to show that metallicity dependence of L<SUB>X</SUB>/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<SUB>⊙</SUB> yr<SUP>-1</SUP>. We speculate that reduced overall stellar ages and 'burstier' star formation histories in the early Universe may lead to higher L<SUB>X</SUB>/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.STAMPAenArticle10.1093/mnras/stab15752-s2.0-85115407760https://academic.oup.com/mnras/article/505/4/4798/62899302021MNRAS.505.4798SFIS/05 - ASTRONOMIA E ASTROFISICA