Estim. dark energy up by 3 percentage points. Any reaction?

[marcus]

When people cite the dark energy fraction informally (without errorbar) and other basic parameters they often have been saying something like

Hubble 71
dark energy 73%
dark matter 23%
baryonic 4%

If I remember right, those are the default values used in the calculator at Ned Wright's website.

Now in this 7 March paper by Michael Turner et al, right in the abstract up front I see

dark energy 76%
dark matter 20%
baryonic 4%

So are these new values that one should quote informally? Given the uncertainty it doesn't seem very different to say 76 instead of 73, but even though it is just a rough estimate I'd like to be aligned with the mainest of the stream---and keep the jarring dissonance to a minimum. So what numbers to you say?

Michael Turner recent:
http://arxiv.org/abs/0803.0982

 

[my_wan]

Cosmology is a field I haven't studied in detail. I have only gone through it enough to know generally what cosmologist are talking about and why. For me my interest in cosmology is limited to what it can provide as a testing ground. Since I don't have any ideas (wild ass guesses) that require these parameters at the moment the ball park figure is fine with me. However, as a cosmologist, keeping abreast and using the best numbers from the best available data is important. Given the authors and the following quotes under "10.1 Take-home facts":

10.1.5 Current observational status. Taken together, all the current
data provide strong evidence for the existence of dark energy; they constrain
the fraction of critical density contributed by dark energy, 0.76 ± 0.02, and the
equation-of-state parameter, w ≈ −1 ± 0.1 (stat) ±0.1 (sys), assuming that w is
constant. This implies that the Universe began accelerating at redshift z ~ 0.4
and age t ~ 10 Gyr. These results are robust – data from anyone method can be
removed without compromising the constraints – and they are not substantially
weakened by dropping the assumption of spatial flatness. <snip>

I would go with these figures.

 

[cristo]

I don't really know where that figure has come from; I guess it depends on what data set you're using. I know the recent WMAP data had omega_lambda 0.74 on its own, and that shrunk to about 0.72 when including other data sets (namely the BAO and SN data). I've not read the Turner paper, though, so I can't really comment on that; perhaps someone else can?

 

[Wallace]

The precise numbers still depend on which data sets are used. For instance see the series of tables http://lambda.gsfc.nasa.gov/product/map/current/parameters.cfm" that show the values obtained using WMAP5 + many different combinations of other data. The best fit values for dark energy vary between 0.7 and almost 0.8 depending on which data sets are used!

There are a bunch of extensions to the basic LCDM such as non flat models, different dark energy models etc that are also covered.