dc.contributor.author Melia, Fulvio dc.date.accessioned 2016-06-30T00:40:52Z dc.date.available 2016-06-30T00:40:52Z dc.date.issued 2016-02-17 dc.identifier.citation Constancy of the cluster gas mass fraction in the Rh=ct Universe 2016, 472 (2186):20150765 Proceedings of the Royal Society A: Mathematical, Physical and Engineering Science en dc.identifier.issn 1364-5021 dc.identifier.issn 1471-2946 dc.identifier.doi 10.1098/rspa.2015.0765 dc.identifier.uri http://hdl.handle.net/10150/615118 dc.description.abstract The ratio of baryonic to dark matter densities is assumed to have remained constant throughout the formation of structure. With this, simulations show that the fraction $f_{\rm gas}(z)$ of baryonic mass to total mass in galaxy clusters should be nearly constant with redshift $z$. However, the measurement of these quantities depends on the angular distance to the source, which evolves with $z$ according to the assumed background cosmology. An accurate determination of $f_{\rm gas}(z)$ for a large sample of hot ($kT_e> 5$ keV), dynamically relaxed clusters could therefore be used as a probe of the cosmological expansion up to $z< 2$. The fraction $f_{\rm gas}(z)$ would remain constant only when the correct" cosmology is used to fit the data. In this paper, we compare the predicted gas mass fractions for both $\Lambda$CDM and the $R_{\rm h}=ct$ Universe and test them against the 3 largest cluster samples \cite{1,2,3}. We show that $R_{\rm h}=ct$ is consistent with a constant $f_{\rm gas}$ in the redshift range $z\lesssim 2$, as was previously shown for the reference $\Lambda$CDM model (with parameter values $H_0=70$ km s$^{-1}$ Mpc$^{-1}$, $\Omega_m=0.3$ and $w_\Lambda=-1$). Unlike $\Lambda$CDM, however, the $R_{\rm h}=ct$ Universe has no free parameters to optimize in fitting the data. Model selection tools, such as the Akaike Information Criterion (AIC) and the Bayes Information Criterion (BIC), therefore tend to favor $R_{\rm h}=ct$ over $\Lambda$CDM. For example, the BIC favours $R_{\rm h}=ct$ with a likelihood of $\sim 95\%$ versus $\sim 5\%$ for $\Lambda$CDM. dc.language.iso en en dc.publisher The Royal Society en dc.relation.url http://rspa.royalsocietypublishing.org/lookup/doi/10.1098/rspa.2015.0765 en dc.rights © 2016 The Author(s) Published by the Royal Society. All rights reserved. en dc.title Constancy of the cluster gas mass fraction in the Rh=ct Universe en dc.type Article en dc.contributor.department The University of Arizona en dc.identifier.journal Proceedings of the Royal Society A: Mathematical, Physical and Engineering Science en dc.description.note Published 17 February 2016. 12 month embargo. en dc.description.collectioninformation This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu. en dc.eprint.version Final accepted manuscript en refterms.dateFOA 2017-02-17T00:00:00Z html.description.abstract The ratio of baryonic to dark matter densities is assumed to have remained constant throughout the formation of structure. With this, simulations show that the fraction $f_{\rm gas}(z)$ of baryonic mass to total mass in galaxy clusters should be nearly constant with redshift $z$. However, the measurement of these quantities depends on the angular distance to the source, which evolves with $z$ according to the assumed background cosmology. An accurate determination of $f_{\rm gas}(z)$ for a large sample of hot ($kT_e> 5$ keV), dynamically relaxed clusters could therefore be used as a probe of the cosmological expansion up to $z< 2$. The fraction $f_{\rm gas}(z)$ would remain constant only when the correct" cosmology is used to fit the data. In this paper, we compare the predicted gas mass fractions for both $\Lambda$CDM and the $R_{\rm h}=ct$ Universe and test them against the 3 largest cluster samples \cite{1,2,3}. We show that $R_{\rm h}=ct$ is consistent with a constant $f_{\rm gas}$ in the redshift range $z\lesssim 2$, as was previously shown for the reference $\Lambda$CDM model (with parameter values $H_0=70$ km s$^{-1}$ Mpc$^{-1}$, $\Omega_m=0.3$ and $w_\Lambda=-1$). Unlike $\Lambda$CDM, however, the $R_{\rm h}=ct$ Universe has no free parameters to optimize in fitting the data. Model selection tools, such as the Akaike Information Criterion (AIC) and the Bayes Information Criterion (BIC), therefore tend to favor $R_{\rm h}=ct$ over $\Lambda$CDM. For example, the BIC favours $R_{\rm h}=ct$ with a likelihood of $\sim 95\%$ versus $\sim 5\%$ for $\Lambda$CDM.
﻿

### Files in this item

Name:
ms.pdf
Size:
449.8Kb
Format:
PDF
Description:
Final Accepted Manuscript