X-Ray Binary Luminosity Function Scaling Relations for Local Galaxies Based on Subgalactic Modeling
Loading...
Links to Files
Author/Creator ORCID
Date
2019-06-26
Type of Work
Department
Program
Citation of Original Publication
Bret D. Lehmer, et.al, X-Ray Binary Luminosity Function Scaling Relations for Local Galaxies Based on Subgalactic Modeling, The Astrophysical Journal Supplement Series, Volume 243, Number 1, https://doi.org/10.5281/zenodo.2875827
Rights
This item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.
©2019 IOP Science
©2019 IOP Science
Abstract
We present new Chandra constraints on the X-ray luminosity functions (XLFs) of X-ray binary (XRB)
populations, as well as their scaling relations, for a sample of 38 nearby galaxies (D = 3.4–29 Mpc). Our galaxy
sample is drawn primarily from the Spitzer Infrared Nearby Galaxies Survey (SINGS) and contains a wealth of
Chandra (5.8 Ms total) and multiwavelength data, allowing for star formation rates (SFRs) and stellar masses (Må)
to be measured on subgalactic scales. We divided the 2478 X-ray-detected sources into 21 subsamples in bins of
specific SFR (sSFR ≡ SFR/Må) and constructed XLFs. To model the XLF dependence on sSFR, we fit a global
XLF model, containing contributions from high-mass XRBs (HMXBs), low-mass XRBs (LMXBs), and
background sources from the cosmic X-ray background that respectively scale with SFR, Må, and sky area. We
find an HMXB XLF that is more complex in shape than previously reported and an LMXB XLF that likely varies
with sSFR, potentially due to an age dependence. When applying our global model to XLF data for each individual
galaxy, we discover a few galaxy XLFs that significantly deviate from our model beyond statistical scatter. Most
notably, relatively low-metallicity galaxies have an excess of HMXBs above ≈10³⁸ erg s⁻¹
, and elliptical galaxies
that have relatively rich populations of globular clusters (GCs) show excesses of LMXBs compared to the global
model. Additional modeling of how the XRB XLF depends on stellar age, metallicity, and GC specific frequency is
required to sufficiently characterize the XLFs of galaxies.