What's the Dark Matter Density in Universe?

In summary, the physical baryon density is 0.02230±0.00014, while the physical dark matter density is 0.1188±0.0010. Matter density is 0.3089±0.0062.
  • #1
RyanH42
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In wikipedia says Physical baryon density: ##Ω_bh^2=0.02230±0.00014## and
Physical dark matter density:##Ω_ch^2=0.1188±0.0010##
Matter density:##Ω_m=0.3089±0.0062##
so If we collect baryonic matter density and dark matter density we cannot get matter density

https://en.wikipedia.org/wiki/Lambda-CDM_model
 
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  • #2
Notice the appearance of h^2 in the values you quote for DM and baryon abundances.
 
  • #3
Lets suppose I want to calculate dark matter mass/baryonic matter mass ? What should I do
 
  • #4
Whats the meaning of ##h^2## in here
 
  • #5
You ignore the h2 which tells you the result scales with H0. Substituting h~0.7 you get the correct results.
 
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  • #6
I got it thanks.
 
  • #7
##h## is the Hubble constant H today divided by 100, i.e., ##h \simeq 0.6780\pm 0.0077## (PLANCK 2013).
 
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  • #8
I add them and I get 0.287 not 0.3089
 
  • #9
RyanH42 said:
I add them and I get 0.287 not 0.3089

What did you use for ##h##? Using 0.678 gives me 0.3069.
 
  • #10
I used 0.49
 
  • #11
You mean you used ##h^2 = 0.49##? For ##h = 0.678## you will get ##h^2 = 0,46##. You should however note that ##h## also comes with an error. The reason that the abundance is given in ##\Omega h^2## is that this quantity is better bounded.
 
  • #12
Yeah I used h2=0.49
 
  • #13
To get the right answer, you have to use the value of ##h## that was used to measure those parameters. As ##h = H_0 / 100 km/s/Mpc##, and ##H_0 = 67.74 km/s/Mpc## in that data set, ##h = 0.6774##. Use that number, and it will work. There will be some small differences, due to the fact that these numbers aren't published with full accuracy. But it'll be well within the errors.
 
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  • #14
Chalnoth said:
To get the right answer, you have to use the value of ##h## that was used to measure those parameters. As ##h = H_0 / 100 km/s/Mpc##, and ##H_0 = 67.74 km/s/Mpc## in that data set, ##h = 0.6774##. Use that number, and it will work. There will be some small differences, due to the fact that these numbers aren't published with full accuracy. But it'll be well within the errors.

Finally.Thank you
 

FAQ: What's the Dark Matter Density in Universe?

What is dark matter and why is it important?

Dark matter is a hypothetical type of matter that makes up about 85% of the total mass of the universe. It does not interact with light or other forms of electromagnetic radiation, making it invisible to telescopes. Its existence is inferred from its gravitational effects on visible matter. Understanding dark matter is important because it plays a crucial role in the formation and evolution of galaxies, and its properties can provide insights into the fundamental nature of the universe.

How do scientists measure the density of dark matter in the universe?

Scientists use a variety of methods to measure the density of dark matter in the universe. One method is through gravitational lensing, where the bending of light by massive objects can reveal the presence of dark matter. Another method is through studying the rotation curves of galaxies, which can indicate the amount of dark matter present. Scientists also use data from the cosmic microwave background to estimate the overall density of dark matter in the universe.

What is the current estimated density of dark matter in the universe?

The current estimated density of dark matter in the universe is about 26.8%, based on data from the European Space Agency's Planck satellite. This means that dark matter makes up about a quarter of the total mass of the universe. However, this is still an active area of research and the exact density may vary depending on the method used for measurement.

What are the potential candidates for dark matter particles?

There are several hypothesized particles that could make up dark matter, including weakly interacting massive particles (WIMPs), axions, and sterile neutrinos. However, none of these particles have been directly observed or confirmed as the source of dark matter. Scientists continue to search for evidence of these and other potential candidates through experiments and observations.

What is the significance of determining the dark matter density in the universe?

Determining the dark matter density in the universe is significant because it can help us understand the overall structure and evolution of the universe. It can also provide insights into the nature of dark matter itself and potentially lead to new discoveries and advancements in our understanding of the universe. Additionally, knowing the density of dark matter can have implications for theories and models of the universe, such as the Big Bang theory and the concept of dark energy.

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