The impact of galaxy formation on X-ray groups

Kay, Scott T, Thomas, Peter A and Theuns, Tom (2003) The impact of galaxy formation on X-ray groups. Monthly Notices of the Royal Astronomical Society, 343 (2). pp. 608-618. ISSN 0035-8711

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Using hydrodynamical simulations of the Λ-cold dark matter cosmology that include both radiative cooling and a phenomenological model for star formation and supernovae feedback, we investigate the impact of galaxy formation on the X-ray properties of groups at zero redshift. Motivated by the observed ‘break’ in the Lx–Tx relation at kTx∼ 1–2 keV, our feedback model is based on the assumption that supernovae imprint a temperature scale on the hot gas, with the star formation rate and corresponding reheated gas mass then depending only on the available energy budget. We demonstrate that a strong feedback model with a heating temperature comparable to this break (kTSN= 2 keV), and an energy budget twice that available from supernovae (ε= 2), raises the core entropy of groups sufficiently to produce an adequate match to their observed X-ray properties. A lower value of ε increases the star formation rate without significantly affecting the X-ray properties of groups, and a model with ε∼ 0.1 reproduces the observed fraction of baryons in stars. However, a heating temperature that is lower than the virial temperatures of the groups leads to an excess of cooling gas that boosts their X-ray luminosities, due to the failure of the reheated material to escape from the gravitational potential. A limited study of numerical resolution effects reveals that the temperature of poorly resolved objects is underestimated, therefore (in our case) a fully resolved group population would lead to a steeper Lx–Tx relation, bringing our results into even better agreement with the observations.

Item Type: Article
Additional Information: Kay was a PDRA and Thomas his supervisor: together they developed and refined the feedback models. Theuns was an external collaborator. This paper demonstrates that there is a plausible feedback mechanism from supernovae that reproduces the X-ray properties of groups.
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Depositing User: Peter Thomas
Date Deposited: 06 Feb 2012 18:46
Last Modified: 04 May 2018 07:40

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