The MOSDEF Survey: The Metallicity Dependence of X-Ray Binary Populations at z ∼ 2

Francesca M. Fornasini, Mariska Kriek, Ryan L. Sanders, Irene Shivaei, Francesca Civano, Naveen A. Reddy, Alice E. Shapley, Alison L. Coil, Bahram Mobasher, Brian Siana, James Aird, Mojegan Azadi, William R. Freeman, Gene C.K. Leung, Sedona H. Price, Tara Fetherolf, Tom Zick, Guillermo Barro

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


Population synthesis models predict that high-mass X-ray binary (HMXB) populations produced in low-metallicity environments should be more X-ray luminous, a trend supported by studies of nearby galaxies. This trend may be responsible for the observed increase of the X-ray luminosity (L X) per star formation rate (SFR) with redshift due to the decrease of metallicity (Z) at fixed stellar mass as a function of redshift. To test this hypothesis, we use a sample of 79 z ∼ 2 star-forming galaxies with oxygen abundance measurements from the MOSDEF survey, which obtained rest-frame optical spectra for ∼1500 galaxies in the CANDELS fields at 1.37 < z < 3.80. Using Chandra data from the Chandra AEGIS-X Deep, Chandra Deep Field North, and Chandra Deep Field South surveys, we stack the X-ray data at the galaxy locations in bins of redshift and Z because the galaxies are too faint to be individually detected. In agreement with previous studies, the average L X/SFR of our z ∼ 2 galaxy sample is enhanced by ≈0.4-0.8 dex relative to local HMXB L X-SFR scaling relations. Splitting our sample by Z, we find that L X/SFR and Z are anticorrelated with 97% confidence. This observed Z dependence for HMXB-dominated galaxies is consistent with both the local L X-SFR-Z relation and a subset of population synthesis models. Although the statistical significance of the observed trends is weak owing to the low X-ray statistics, these results constitute the first direct evidence connecting the redshift evolution of L X/SFR and the Z dependence of HMXBs.

Original languageEnglish
Article number65
JournalAstrophysical Journal
Issue number1
StatePublished - Nov 1 2019

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© 2019. The American Astronomical Society. All rights reserved.

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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