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2014MNRAS.441..964R - Mon. Not. R. Astron. Soc., 441, 964-982 (2014/June-3)

Feedback from winds and supernovae in massive stellar clusters - II. X-ray emission.

ROGERS H. and PITTARD J.M.

Abstract (from CDS):

The X-ray emission from a simulated massive stellar cluster is investigated. The emission is calculated from a 3D hydrodynamical model which incorporates the mechanical feedback from the stellar winds of three O stars embedded in a giant molecular cloud (GMC) clump containing 3240M of molecular material within a 4pc radius. A simple prescription for the evolution of the stars is used, with the first supernova (SN) explosion at t = 4.4Myr. We find that the presence of the GMC clump causes short-lived attenuation effects on the X-ray emission of the cluster. However, once most of the material has been ablated away by the winds, the remaining dense clumps do not have a noticeable effect on the attenuation compared with the assumed interstellar medium (ISM) column. We determine the evolution of the cluster X-ray luminosity, LX, and spectra, and generate synthetic images. The intrinsic X-ray luminosity drops from nearly 1034 erg/s while the winds are `bottled up', to a near-constant value of 1.7x1032 erg/s between t = 1 and 4Myr. LX reduces slightly during each star's red supergiant stage due to the depressurization of the hot gas. However, LX increases to ~ 1034 erg/s during each star's Wolf-Rayet stage. The X-ray luminosity is enhanced by two to three orders of magnitude to ∼ 1037 erg/s for at least 4600yr after each SN explosion, at which time the blast wave leaves the grid and the X-ray luminosity drops. The X-ray luminosity of our simulation is generally considerably fainter than predicted from spherically symmetric bubble models, due to the leakage of hot gas material through gaps in the outer shell. This process reduces the pressure within our simulation and thus the X-ray emission. However, the X-ray luminosities and temperatures which we obtain are comparable to similarly powerful massive young clusters.