X-ray emission from star-forming galaxies – I. High-mass X-ray binaries
Version of Record online: 18 NOV 2011
© 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS
Monthly Notices of the Royal Astronomical Society
Volume 419, Issue 3, pages 2095–2115, January 2012
How to Cite
Mineo, S., Gilfanov, M. and Sunyaev, R. (2012), X-ray emission from star-forming galaxies – I. High-mass X-ray binaries. Monthly Notices of the Royal Astronomical Society, 419: 2095–2115. doi: 10.1111/j.1365-2966.2011.19862.x
- Issue online: 4 JAN 2012
- Version of Record online: 18 NOV 2011
- Accepted 2011 September 20. Received 2011 September 20; in original form 2011 May 19
- stars: formation;
- galaxies: irregular;
- galaxies: spiral;
- galaxies: starburst;
- X-rays: binaries;
- X-rays: galaxies
Based on a homogeneous set of X-ray, infrared and ultraviolet observations from Chandra, Spitzer, GALEX and 2MASS archives, we study populations of high-mass X-ray binaries (HMXBs) in a sample of 29 nearby star-forming galaxies and their relation to the star-formation rate (SFR). In agreement with previous results, we find that HMXBs are a good tracer of the recent star-formation activity in the host galaxy and their collective luminosity and number scale with the SFR: in particular, . However, the scaling relations still bear a rather large dispersion of rms ∼ 0.4 dex, which we believe is of a physical origin.
We present the catalogue of 1055 X-ray sources detected within the D25 ellipse for galaxies of our sample and construct the average X-ray luminosity function (XLF) of HMXBs with substantially improved statistical accuracy and better control of systematic effects than achieved in previous studies. The XLF follows a power law with a slope of 1.6 in the log (LX) ∼ 35–40 luminosity range with moderately significant evidence for a break or cut-off at LX∼ 1040 erg s−1. As before, we did not find any features at the Eddington limit for a neutron star or a stellar-mass black hole.
We discuss the implications of our results for the theory of binary evolution. In particular we estimate the fraction of compact objects that once in their lifetime experienced an X-ray active phase powered by accretion from a high-mass companion and obtain a rather large number, fX∼ 0.2 × (0.1 Myr/τX), where τX is the lifetime of the X-ray active phase. This is ∼4 orders of magnitude more frequent than in low-mass X-ray binaries (LMXBs). We also derive constraints on the mass distribution of the secondary star in HMXBs.