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

2019; IOP Publishing; Volume: 885; Issue: 1 Linguagem: Inglês

10.3847/1538-4357/ab4653

1538-4357

Francesca M. Fornasini, Mariska Kriek, Ryan L. Sanders, Irene Shivaei, F. 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,

Gamma-ray bursts and supernovae

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 ($L_{\mathrm{X}}$) 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 $z\sim2$ star-forming galaxies with oxygen abundance measurements from the MOSDEF survey, which obtained rest-frame optical spectra for $\sim1500$ galaxies in the CANDELS fields at $1.37<z<3.80$. Using Chandra data from the AEGIS-X Deep, Deep Field North, and 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 $L_{\mathrm{X}}$/SFR of our $z\sim2$ galaxy sample is enhanced by $\approx0.4-0.8$ dex relative to local HMXB $L_{\mathrm{X}}$-SFR scaling relations. Splitting our sample by $Z$, we find that $L_{\mathrm{X}}$/SFR and $Z$ are anti-correlated with 97% confidence. This observed $Z$ dependence for HMXB-dominated galaxies is consistent both with the local $L_{\mathrm{X}}$-SFR-$Z$ relation and a subset of population synthesis models. Although the statistical significance of the observed trends is weak due to the low X-ray statistics, these results constitute the first direct evidence connecting the redshift evolution of $L_{\mathrm{X}}$/SFR and the $Z$ dependence of HMXBs.