Rotation curve with neutral hydrogen and dark matter

In summary: The solar system as a whole has a much higher density than the galactic disk in terms of baryonic matter. So even though the density of dark matter is roughly the same, the ratio of baryonic to dark matter in the solar system is extremely high compared to the disk as whole. Thus in the solar system, baryonic matter dominates the orbital dynamics, while in the disk as a whole, dark matter contributes to a larger percentage of the gravitational interaction.
  • #1
Ranku
420
18
Flat rotation curve in galaxies is determined by observing neutral hydrogen which is co-distributed with dark matter. What is the rotation curve profile of neutral hydrogen in galaxies where there is less dark matter?
 
Astronomy news on Phys.org
  • #2
How is neutral hydrogen observed?
 
  • #3
mathman said:
How is neutral hydrogen observed?
Through 21-centimetre radio emission arising out of collision between neutral hydrogen atoms.
 
  • #4
Keplerian.
 
  • #5
stefan r said:
Keplerian.
So is the flat rotation curve only due to the presence of more matter in the form of dark matter, or is it also due to some unexplained property of dark matter.
 
  • #6
Ranku said:
So is the flat rotation curve only due to the presence of more matter in the form of dark matter, or is it also due to some unexplained property of dark matter.
The disc structure is very common at all scales of rotating groups of objects in space. From what I understand, dark matter is not needed to explain small scale phenomena (Solar System). Is it needed for galactic rotation explanation?
 
  • #7
sophiecentaur said:
The disc structure is very common at all scales of rotating groups of objects in space. From what I understand, dark matter is not needed to explain small scale phenomena (Solar System). Is it needed for galactic rotation explanation?
Velocity dispersion in outer regions of galaxies are higher than expected, indicating presence of more matter than the visible matter, which are mostly concentrated toward the centre.
 
  • Like
Likes sophiecentaur
  • #8
sophiecentaur said:
The disc structure is very common at all scales of rotating groups of objects in space. From what I understand, dark matter is not needed to explain small scale phenomena (Solar System). Is it needed for galactic rotation explanation?
The solar system as a whole has a much higher density than the galactic disk in terms of baryonic matter. So even though the density of
DM is roughly the same, the ratio of baryonic to dark matter in the solar system is extremely high compared to the disk as whole. Thus in the solar system, baryonic matter dominates the orbital dynamics, while in the disk as a whole, DM contributes to a larger percentage of the gravitational interaction.
 
  • Like
Likes sophiecentaur

Related to Rotation curve with neutral hydrogen and dark matter

1. What is a rotation curve?

A rotation curve is a graph that shows the relationship between the rotational velocity of a galaxy and its distance from the center. It is typically measured by observing the Doppler shift of neutral hydrogen gas in the galaxy.

2. How is neutral hydrogen used to study rotation curves?

Neutral hydrogen emits radio waves at a specific frequency, which can be observed using radio telescopes. By measuring the Doppler shift of these radio waves, we can determine the rotational velocity of the gas and use it to create a rotation curve for the galaxy.

3. What is the role of dark matter in rotation curves?

Dark matter is believed to make up a large portion of the mass in galaxies. Its presence can be inferred from the observed rotation curves, as the rotational velocities of stars and gas in the outer regions of galaxies are much higher than expected based on the visible matter alone. This suggests the presence of additional mass, which is attributed to dark matter.

4. How does dark matter affect the shape of a rotation curve?

Dark matter has a significant impact on the shape of a rotation curve. In most cases, the rotation curve will rise rapidly at first and then flatten out as the distance from the center increases. This is because the gravitational pull of dark matter is stronger in the outer regions of a galaxy, causing the stars and gas to rotate at higher speeds.

5. Can rotation curves be used to study the distribution of dark matter in a galaxy?

Yes, rotation curves are a valuable tool for studying the distribution of dark matter in galaxies. By analyzing the shape and velocity of the rotation curve, scientists can make inferences about the amount and distribution of dark matter in a galaxy. This can help us better understand the role of dark matter in the formation and evolution of galaxies.

Similar threads

  • Astronomy and Astrophysics
2
Replies
40
Views
3K
  • Astronomy and Astrophysics
Replies
32
Views
3K
  • Astronomy and Astrophysics
Replies
3
Views
2K
  • Astronomy and Astrophysics
Replies
5
Views
1K
  • Astronomy and Astrophysics
Replies
14
Views
2K
  • Astronomy and Astrophysics
Replies
4
Views
715
  • Astronomy and Astrophysics
Replies
4
Views
2K
  • Astronomy and Astrophysics
Replies
1
Views
930
Replies
10
Views
1K
  • Astronomy and Astrophysics
Replies
1
Views
1K
Back
Top