# THE AGE–REDSHIFT RELATIONSHIP OF OLD PASSIVE GALAXIES

http://hdl.handle.net/10150/615092
Title:
THE AGE–REDSHIFT RELATIONSHIP OF OLD PASSIVE GALAXIES
Author:
Wei, Jun-Jie; Wu, Xue-Feng; Melia, Fulvio; Wang, Fa-Yin; Yu, Hai
Affiliation:
The University of Arizona
Issue Date:
2015-07-07
Publisher:
IOP PUBLISHING LTD
Citation:
THE AGE–REDSHIFT RELATIONSHIP OF OLD PASSIVE GALAXIES 2015, 150 (1):35 The Astronomical Journal
Journal:
The Astronomical Journal
Rights:
Collection Information:
Abstract:
We use 32 age measurements of passively evolving galaxies as a function of redshift to test and compare the standard model ($\Lambda$CDM) with the $R_{\rm h}=ct$ Universe. We show that the latter fits the data with a reduced $\chi^2_{\rm dof}=0.435$ for a Hubble constant $H_{0}= 67.2_{-4.0}^{+4.5}$ km $\rm s^{-1}$ $\rm Mpc^{-1}$. By comparison, the optimal flat $\Lambda$CDM model, with two free parameters (including $\Omega_{\rm m}=0.12_{-0.11}^{+0.54}$ and $H_{0}=94.3_{-35.8}^{+32.7}$ km $\rm s^{-1}$ $\rm Mpc^{-1}$), fits the age-\emph{z} data with a reduced $\chi^2_{\rm dof}=0.428$. Based solely on their $\chi^2_{\rm dof}$ values, both models appear to account for the data very well, though the optimized $\Lambda$CDM parameters are only marginally consistent with those of the concordance model ($\Omega_{\rm m}=0.27$ and $H_{0}= 70$ km $\rm s^{-1}$ $\rm Mpc^{-1}$). Fitting the age-$z$ data with the latter results in a reduced $\chi^2_{\rm dof}=0.523$. However, because of the different number of free parameters in these models, selection tools, such as the Akaike, Kullback and Bayes Information Criteria, favour $R_{\rm h}=ct$ over $\Lambda$CDM with a likelihood of $\sim 66.5\%-80.5\%$ versus $\sim 19.5\%-33.5\%$. These results are suggestive, though not yet compelling, given the current limited galaxy age-$z$ sample. We carry out Monte Carlo simulations based on these current age measurements to estimate how large the sample would have to be in order to rule out either model at a $\sim 99.7\%$ confidence level. We find that if the real cosmology is $\Lambda$CDM, a sample of $\sim 45$ galaxy ages would be sufficient to rule out $R_{\rm h}=ct$ at this level of accuracy, while $\sim 350$ galaxy ages would be required to rule out $\Lambda$CDM if the real Universe were instead $R_{\rm h}=ct$. This difference in required sample size reflects the greater number of free parameters available to fit the data with $\Lambda$CDM.
ISSN:
1538-3881
DOI:
10.1088/0004-6256/150/1/35
Version:
Final accepted manuscript
http://stacks.iop.org/1538-3881/150/i=1/a=35?key=crossref.fd206a847a507970772890ba98a1a896

DC FieldValue Language
dc.contributor.authorWei, Jun-Jieen
dc.contributor.authorWu, Xue-Fengen
dc.contributor.authorMelia, Fulvioen
dc.contributor.authorWang, Fa-Yinen
dc.contributor.authorYu, Haien
dc.date.accessioned2016-06-29T19:30:03Z-
dc.date.available2016-06-29T19:30:03Z-
dc.date.issued2015-07-07-
dc.identifier.citationTHE AGE–REDSHIFT RELATIONSHIP OF OLD PASSIVE GALAXIES 2015, 150 (1):35 The Astronomical Journalen
dc.identifier.issn1538-3881-
dc.identifier.doi10.1088/0004-6256/150/1/35-
dc.identifier.urihttp://hdl.handle.net/10150/615092-
dc.description.abstractWe use 32 age measurements of passively evolving galaxies as a function of redshift to test and compare the standard model ($\Lambda$CDM) with the $R_{\rm h}=ct$ Universe. We show that the latter fits the data with a reduced $\chi^2_{\rm dof}=0.435$ for a Hubble constant $H_{0}= 67.2_{-4.0}^{+4.5}$ km $\rm s^{-1}$ $\rm Mpc^{-1}$. By comparison, the optimal flat $\Lambda$CDM model, with two free parameters (including $\Omega_{\rm m}=0.12_{-0.11}^{+0.54}$ and $H_{0}=94.3_{-35.8}^{+32.7}$ km $\rm s^{-1}$ $\rm Mpc^{-1}$), fits the age-\emph{z} data with a reduced $\chi^2_{\rm dof}=0.428$. Based solely on their $\chi^2_{\rm dof}$ values, both models appear to account for the data very well, though the optimized $\Lambda$CDM parameters are only marginally consistent with those of the concordance model ($\Omega_{\rm m}=0.27$ and $H_{0}= 70$ km $\rm s^{-1}$ $\rm Mpc^{-1}$). Fitting the age-$z$ data with the latter results in a reduced $\chi^2_{\rm dof}=0.523$. However, because of the different number of free parameters in these models, selection tools, such as the Akaike, Kullback and Bayes Information Criteria, favour $R_{\rm h}=ct$ over $\Lambda$CDM with a likelihood of $\sim 66.5\%-80.5\%$ versus $\sim 19.5\%-33.5\%$. These results are suggestive, though not yet compelling, given the current limited galaxy age-$z$ sample. We carry out Monte Carlo simulations based on these current age measurements to estimate how large the sample would have to be in order to rule out either model at a $\sim 99.7\%$ confidence level. We find that if the real cosmology is $\Lambda$CDM, a sample of $\sim 45$ galaxy ages would be sufficient to rule out $R_{\rm h}=ct$ at this level of accuracy, while $\sim 350$ galaxy ages would be required to rule out $\Lambda$CDM if the real Universe were instead $R_{\rm h}=ct$. This difference in required sample size reflects the greater number of free parameters available to fit the data with $\Lambda$CDM.en
dc.language.isoenen
dc.publisherIOP PUBLISHING LTDen
dc.relation.urlhttp://stacks.iop.org/1538-3881/150/i=1/a=35?key=crossref.fd206a847a507970772890ba98a1a896en
dc.titleTHE AGE–REDSHIFT RELATIONSHIP OF OLD PASSIVE GALAXIESen
dc.typeArticleen
dc.contributor.departmentThe University of Arizonaen
dc.identifier.journalThe Astronomical Journalen
dc.eprint.versionFinal accepted manuscripten