Curve fitting the luminosity distance and redshift data

  • #1
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Main Question or Discussion Point

Can anyone recommend papers that directly curve-fit redshift as a function of luminosity distance for type Ia supernova and gamma ray bursts? I am looking for papers that do not curve-fit the data via an assumed model, even one as simple as Friedmann–Lemaître–Robertson–Walker (FLRW) metric. I am really just curious to see what the following function ##f## might look like, where ##z## denotes redshift and ##d_l## denotes luminosity distance:

##z = f(d_l) ##
 

Answers and Replies

  • #2
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You need some assumptions for f to do curve fitting. The "best fit" is a function that attains the best estimate for z at the best estimate for dl for every single measurement exactly, but that won't give a realistic function.
 
  • #3
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Sure, but the assumptions for ##f## can be about the relationship between the variables (linear? exponential? trigonometric? etc.) without assuming a particular physical model.

Has anyone published the "best fit" function for ##z## as a function of ##d_l## WITHOUT first assuming a particular physical model?
 
  • #4
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Linear, exponential, trigonometric etc. all don't fit. Mathematically you can do it but the fit quality is just too bad to publish it.
 
  • #5
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Is there an online repository of the data out to high ##z## that is downloadable for analysis?
 
  • #6
kimbyd
Science Advisor
Gold Member
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Is there an online repository of the data out to high ##z## that is downloadable for analysis?
Depends upon what you mean by high-z. Easiest to work with is probably supernova data. One relatively recent compilation is here, at the Supernova Cosmology Project:
http://supernova.lbl.gov/union/

They have published a summary table of the per-supernova distance/redshift relation:
http://supernova.lbl.gov/union/figures/SCPUnion2.1_mu_vs_z.txt

You'd have to read their papers to understand what the various columns of that table are, to apply them to your own fit. Looks like they go out to a redshift of about 1.4 or so.
 

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