Connecting the metallicity dependence and redshift evolution of high-mass X-ray binaries
Monthly Notices of the Royal Astronomical Society(2020)
摘要
The integrated X-ray luminosity (L
X
) of high-mass X-ray binaries (HMXBs) in a galaxy is correlated with its star formation rate (SFR), and the normalization of this correlation increases with redshift. Population synthesis models suggest that the redshift evolution of L
X
/SFR is driven by the metallicity (Z) dependence of HMXBs, and the first direct evidence of this connection was recently presented using galaxies at z ∼ 2. To confirm this result with more robust measurements and better constrain the L
X
–SFR–Z relation, we have studied the Z dependence of L
X
/SFR at lower redshifts. Using samples of star-forming galaxies at z = 0.1–0.9 with optical spectra from the hCOSMOS and zCOSMOS surveys, we stacked Chandra data from the COSMOS Legacy survey to measure the average L
X
/SFR as a function of Z in three redshift ranges: z = 0.1–0.25, 0.25–0.4, and 0.5–0.9. We find no significant variation of the L
X
–SFR–Z relation with redshift. Our results provide further evidence that the Z dependence of HMXBs is responsible for the redshift evolution of L
X
/SFR. Combining all available z > 0 measurements together, we derive a best-fitting L
X
–SFR–Z relation and assess how different population synthesis models describe the data. These results provide the strongest constraints to date on the L
X
–SFR–Z relation in the range of 8.0 < 12 + log(O/H) < 9.0.
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关键词
galaxies: abundances,X-rays: binaries,X-rays: galaxies
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