Diffuse, Non-Thermal X-ray Emission from the Galactic Star Cluster Westerlund 1
| dc.creator | Muno, Michael P. | |
| dc.creator | Law, Casey | |
| dc.creator | Clark, J. Simon | |
| dc.creator | Dougherty, Sean M. | |
| dc.creator | de Grijs, Richard | |
| dc.creator | Zwart, Simon Portegies | |
| dc.creator | Yusef-Zadeh, Farhad | |
| dc.date | 2006-06-20 | |
| dc.date.accessioned | 2026-07-07T10:39:20Z | |
| dc.date.available | 2026-07-07T10:39:20Z | |
| dc.description | We present the diffuse X-ray emission identified in Chandra observations of the young, massive Galactic star cluster Westerlund 1. After removing point-like X-ray sources down to a completeness limit of 2e31 erg/s, we identify 3e34 erg/s (2--8 keV) of diffuse emission. The spatial distribution of the emission can be described as a slightly-elliptical Lorentzian core with a half-width half-maximum along the major axis of 25+/-1", similar to the distribution of point sources in the cluster, plus a 5' halo of extended emission. The spectrum of the diffuse emission is dominated by a hard continuum component that can be described as a kT>3 keV thermal plasma that has a low iron abundance (<0.3 solar), or as non-thermal emission that could be stellar light that is inverse-Compton scattered by MeV electrons. Only 5% of the flux is produced by a kT=0.7 keV plasma. The low luminosity of the thermal emission and the lack of a 6.7 keV iron line suggests that <40,000 unresolved stars with masses between 0.3 and 2 Msun are present in the cluster. Moreover, the flux in the diffuse emission is a factor of two lower than would be expected from a supersonically-expanding cluster wind, and there is no evidence for thermal remnants produced by supernovae. Less than 1e-5 of the mechanical luminosity of the cluster is dissipated as 2--8 keV X-rays, leaving a large amount of energy that either is radiated at other wavelengths, is dissipated beyond the bounds of our image, or escapes into the intergalactic medium. | |
| dc.description | 10 pages, 3 figures (one color), and 3 tables. Accepted to ApJ | |
| dc.identifier | https://arxiv.org/abs/astro-ph/0606492 | |
| dc.identifier | http://arxiv.org/abs/astro-ph/0606492 | |
| dc.identifier | Astrophys.J.650:203-211,2006 | |
| dc.identifier | doi:10.1086/507175 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/180991 | |
| dc.subject | Astrophysics | |
| dc.title | Diffuse, Non-Thermal X-ray Emission from the Galactic Star Cluster Westerlund 1 | |
| dc.type | text |