Constancy of the cluster gas mass fraction in the Rh=ct Universe

http://hdl.handle.net/10150/615118
Title:
Constancy of the cluster gas mass fraction in the Rh=ct Universe
Author:
Melia, F. ( 0000-0002-8014-0593 )
Affiliation:
The University of Arizona
Issue Date:
2016-02-17
Publisher:
The Royal Society
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
Journal:
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Science
Rights:
Collection Information:
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.
Note:
Published 17 February 2016. 12 month embargo.
ISSN:
1364-5021; 1471-2946
DOI:
10.1098/rspa.2015.0765
Version:
Final accepted manuscript
http://rspa.royalsocietypublishing.org/lookup/doi/10.1098/rspa.2015.0765

DC FieldValue Language
dc.contributor.authorMelia, F.en
dc.date.accessioned2016-06-30T00:40:52Z-
dc.date.available2016-06-30T00:40:52Z-
dc.date.issued2016-02-17-
dc.identifier.citationConstancy 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 Scienceen
dc.identifier.issn1364-5021-
dc.identifier.issn1471-2946-
dc.identifier.doi10.1098/rspa.2015.0765-
dc.identifier.urihttp://hdl.handle.net/10150/615118-
dc.description.abstractThe 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.en
dc.language.isoenen
dc.publisherThe Royal Societyen
dc.relation.urlhttp://rspa.royalsocietypublishing.org/lookup/doi/10.1098/rspa.2015.0765en
dc.titleConstancy of the cluster gas mass fraction in the Rh=ct Universeen
dc.typeArticleen
dc.contributor.departmentThe University of Arizonaen
dc.identifier.journalProceedings of the Royal Society A: Mathematical, Physical and Engineering Scienceen
dc.description.notePublished 17 February 2016. 12 month embargo.en
dc.eprint.versionFinal accepted manuscripten