The MOSDEF Survey: The Metallicity Dependence of X-ray Binary Populations at $zsim2$. (arXiv:1909.08635v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Fornasini_F/0/1/0/all/0/1">Francesca M. Fornasini</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kriek_M/0/1/0/all/0/1">Mariska Kriek</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sanders_R/0/1/0/all/0/1">Ryan L. Sanders</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shivaei_I/0/1/0/all/0/1">Irene Shivaei</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Civano_F/0/1/0/all/0/1">Francesca Civano</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Reddy_N/0/1/0/all/0/1">Naveen A. Reddy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shapley_A/0/1/0/all/0/1">Alice E. Shapley</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Coil_A/0/1/0/all/0/1">Alison L. Coil</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mobasher_B/0/1/0/all/0/1">Bahram Mobasher</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Siana_B/0/1/0/all/0/1">Brian Siana</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Aird_J/0/1/0/all/0/1">James Aird</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Azadi_M/0/1/0/all/0/1">Mojegan Azadi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Freeman_W/0/1/0/all/0/1">William R. Freeman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Leung_G/0/1/0/all/0/1">Gene C. K. Leung</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Price_S/0/1/0/all/0/1">Sedona H. Price</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fetherolf_T/0/1/0/all/0/1">Tara Fetherolf</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zick_T/0/1/0/all/0/1">Tom Zick</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Barro_G/0/1/0/all/0/1">Guillermo Barro</a>
Population synthesis models predict that high-mass X-ray binary (HMXB) Population synthesis models predict that high-mass X-ray binary (HMXB) http://arxiv.org/icons/sfx.gif
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 $zsim2$ 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
$1.37
populations produced in low metallicity environments should be more X-ray
luminous, a trend supported by studies of nearby galaxies. This trend may be
responsible for the observed increase of the X-ray luminosity
($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 $zsim2$ 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 $zsim2$ 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.
