I How well do cosmological models explain the observed µ vs. z data?

[JimJCW]

The following figure shows observed distance modulus (µ) vs. redshift (z) data (references of data sources are available):

How well do cosmological models, such as ΛCDM and models based on non-expanding universe, explain these observed data?

For explanation of terms, please see,

Type Ia supernova​

γ-ray burst​

Distance modulus​

 

[anorlunda]

(references of data sources are available)

On PF, please provide links to the references in the first post.

 

[JimJCW]

On PF, please provide links to the references in the first post.

My supernova data are from,

Supernova Cosmology Project Union2.1​

http://supernova.lbl.gov/Union/​

​

MLCS2k2 Full Sample ​

https://arxiv.org/pdf/astro-ph/0402512.pdf​

My γ-ray burst data are from,

Bradley E. Schaefer, 2007, The Astrophysical Journal, 660:16-46, 2007​

https://arxiv.org/pdf/astro-ph/0612285.pdf​

​

Hao Wei, Journal of Cosmology and Astroparticle Physics, Issue 08, id. 020 (2010)​

https://arxiv.org/pdf/1004.4951v3.pdf​

 

[phyzguy]

How well do cosmological models, such as ΛCDM and models based on non-expanding universe, explain these observed data?

Lambda-CDM fits quite well. See, for example, Figure 2 from this paper:

https://arxiv.org/pdf/1811.02590.pdf

 

[JimJCW]

Lambda-CDM fits quite well. See, for example, Figure 2 from this paper:

https://arxiv.org/pdf/1811.02590.pdf

The authors of the paper are saying that according to their analysis, the µ vs. z relation of quasars at z<1.4 is qualitatively in agreement with that of supernovae and with the LCDM model. The data, however, suggest a dark energy density increasing with time. As we know, the dark energy density remains constant in the LCDM model.

The data points in our figure are from Type Ia supernovae and γ-ray bursts. It covers a greater range, up to z=8.1.

 

[phyzguy]

The authors of the paper are saying that according to their analysis, the µ vs. z relation of quasars at z<1.4 is qualitatively in agreement with that of supernovae and with the LCDM model. The data, however, suggest a dark energy density increasing with time. As we know, the dark energy density remains constant in the LCDM model.

The data points in our figure are from Type Ia supernovae and γ-ray bursts. It covers a greater range, up to z=8.1.

The data points in the paper I linked go up to z=5, and still seem to fit quite well. Whether or not the observational data is consistent with Lanmbda-CDM , or a model with a varying dark energy is needed is an question which is still being studied. There is no compelling data that supports a dark energy varying with time, but there might be in the future. It is still an open question.

 

[JimJCW]

The data points in the paper I linked go up to z=5, and still seem to fit quite well. Whether or not the observational data is consistent with Lambda-CDM , or a model with a varying dark energy is needed is an question which is still being studied. There is no compelling data that supports a dark energy varying with time, but there might be in the future. It is still an open question.

I think we can summarize this part of the discussion as follows,

The µ vs. z data points of quasars presented in the paper for 0.5<z<5.5 are not inconsistent with those plotted in our (supernova)+(gamma-ray burst) figure. They are additional data points.

There may be some open questions associated with the quasar data. For now, we might want to limit ourselves to the data plotted in our figure to discuss the question of how well some cosmological models do. Note that if there is a time-dependence of dark energy density with time, it probably would show up in the µ vs. z data we use also.

An interesting point to note about dark energy in the universe is that, according the LCDM model, its value continues to increase with space expansion (as indicated by the figure obtained from Jorrie’s calculator), but its density remains constant.

 

[JimJCW]

How well do cosmological models, such as ΛCDM and models based on non-expanding universe, explain these observed data?

The following figure shows µ vs. z plot calculated with the ΛCDM model. It was obtained using Jorrie’s calculator and Planck data (2015), with the help of Eqs. (21) and (25) in Hogg’s article, Distance measures in cosmology. The calculation result suggests that the ΛCDM model can explain the observed µ vs. z data quite well.

 

[JimJCW]

How well do cosmological models, such as ΛCDM and models based on non-expanding universe, explain these observed data?

Fig. 2 of Sorrell’s 2009 paper, Misconceptions about the Hubble recession law, shows the result of a model based on non-expanding universe:

 

[PeterDonis]

Fig. 2 of Sorrell’s 2009 paper, Misconceptions about the Hubble recession law, shows the result of a model based on non-expanding universe:

Only out to $z = 2$. The graph shown for the $\Lambda C D M$ model has data out to $z = 8$. A hypothesis has to account for all of the data, not just a subset that happens to match.

Also, the $\mu$ vs. $z$ data is not the only data that needs to be accounted for.

 

[Vanadium 50]

Sorrell’s 2009 paper

Tired light.
Tired hypothesis.
https://en.wikipedia.org/wiki/Tired_light