Effects of Metallicity on High Mass X-ray Binary Formation

Abstract

The heating of the intergalactic medium in the early, metal-poor Universe may have been partly due to radiation from high mass X-ray binaries (HMXBs). Previous investigations on the effect of metallicity have used galaxies of different types. To isolate the effects of metallicity on the production of HMXBs, we study a sample consisting only of 46 blue compact dwarf galaxies (BCDs) covering metallicity in the range 12+log(O/H) of 7.15 to 8.66. To test the hypothesis of metallicity dependence in the X-ray luminosity function (XLF), we fix the XLF form to that found for near-solar metallicity galaxies and use a Bayesian method to constrain the XLF normalization as a function of star formation rate (SFR) for three different metallicity ranges in our sample. We find an increase by a factor of 4.45 $\pm$ 2.04 in the XLF normalization between the metallicity ranges 7.1-7.7 and 8.2-8.66 at a statistical significance of 99.79 per cent. Our results suggest that HMXB production is enhanced at low metallicity, and consequently that HMXBs may have contributed significantly to the reheating of the early Universe.

7 pages, 3 figures, 5 tables. Accepted for publication in MNRAS on October 14, 2019

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Cited by in corpus (4)

• The Metallicity Dependence of the High-Mass X-ray Binary Luminosity Function
• Connecting the metallicity dependence and redshift evolution of high-mass X-ray binaries
• On the contribution of the X-ray source to the extended nebular HeII emission in IZw18
• Multiwavelength Characterization of the High Mass X-ray Binary Population of M31