Through 21-centimetre radio emission arising out of collision between neutral hydrogen atoms.mathman said:How is neutral hydrogen observed?
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.stefan r said:Keplerian.
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?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.
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.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 ofsophiecentaur 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?
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.
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.
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.
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.
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.