TAG | Largest galactic cluster discovered: explained with dark energy |
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| by William Atkins | |
| Tuesday, 26 August 2008 | |
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Page 2 of 2 Dark energy is a hypothetic (exotic) form of energy that permeates all of the space of the universe and that astronomers think may cause the accelerated expansion of the universe. The outward force of dark energy prevents most large galactic clusters from forming today. However, in the early history of the universe (which is believed to be about 13.7 billion years old), galactic clusters are predicted to more easily have formed. The conclusions of the study have been written in the journal Astronomy & Astrophysics. The title of the paper is “2XMM J083026+524133: the most X-ray luminous cluster at redshift 1.” It is authored by: G. Lamer, M. Hoeft, J. Kohnert, A. Schwope, and J. Storm, all associated with the Astrophysikalisches Institut Potsdam (Potsdam Astrophysics Institute), Potsdam, Germany. They state in the abstract to their paper, “In the distant universe X-ray luminous clusters of galaxies are rare objects. Large area surveys are therefore needed to probe the high luminosity end of the cluster population at redshifts z >= 1. We correlated extended X-ray sources from the second XMM-Newton source catalogue (2XMM) with the SDSS in order to identify new clusters of galaxies. Distant cluster candidates in empty SDSS fields were imaged in the R and z bands with the Large Binocular Telescope. We extracted the X-ray spectra of the cluster candidates and fitted thermal plasma models to the data. We determined the redshift 0.99 +-0.03 for 2XMM J083026+524133 from its X-ray spectrum. With a bolometric luminosity of 1.8 x 10^45 erg/sec this is the most X-ray luminous cluster at redshifts z >= 1. We measured a gas temperature of 8.2 +- 0.9 keV and and estimate a cluster mass M(500) = 5.6 x 10^14 M(solar). The optical imaging revealed a rich cluster of galaxies.” Further information is found on the ESA website “Discovery of the most massive cluster of galaxies known in the distant Universe.”
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