Clustering between high-mass x-ray binaries and ob associations in the milky way

Abstract

We present the first direct measurement of the spatial cross-correlation function of high-mass X-ray binaries (HMXBs) and active OB star-forming complexes in the Milky Way. This result relied on a sample containing 79 hard X-ray-selected HMXBs and 458 OB associations. Clustering between the two populations is detected with a significance above 7σ for distances <1kpc. Thus, HMXBs closely trace the underlying distribution of the massive star-forming regions that are expected to produce the progenitor stars of HMXBs. The average offset of 0.4 0.2kpc between HMXBs and OB associations is consistent with being due to natal kicks at velocities of the order of 100 50kms-1. The characteristic scale of the correlation function suggests an average kinematical age (since the supernova phase) of 4Myr for the HMXB population. Despite being derived from a global view of our Galaxy, these signatures of HMXB evolution are consistent with theoretical expectations as well as observations of individual objects. © 2012. The American Astronomical Society. All rights reserved.