Galaxy Rotation Curves: Impact of Angle on Velocity and Shape

In summary, spectral lines of spiral arms are typically adjusted to account for the angle between the galaxy's plane and our line of sight in order to create a velocity curve. However, when a galaxy is directly face-on to our view, no Doppler velocity can be measured due to the cosmological redshift. This angle between line of sight and galactic plane can influence the shape of the rotation curves, as seen in the case of M33 which has a steadily rising rotation curve despite not being edge-on. There may be a relation between the galaxy's angle relative to our line of sight and the shape of the rotation curve, with the projected rotation velocity being equal to the actual rotation velocity multiplied by the sine of the angle.
  • #1
TrickyDicky
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Usually spectral lines of spiral arms are corrected for the angle of the galaxy plane with respect to our line of sight to give a velocity curve. I guess this works except in the case when the galaxy is exactly "face-on" from our view (at 90 degrees angle from our line of sight) where no Doppler velocity can be measured overimposed to the cosmological redshift.
Does the angle between line of sight and galactic plane influence the shape of the curves?
For instance I have seen rotation curves of M33 which is not edge-on and the rotation curve is not flat in this case,but raises steadily. http://www.hep.shef.ac.uk/research/dm/images/rotationCurve.jpg
Anyone knows of some relation between galaxy angle wrt our line of sight and shape of the rotation curve?
 
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  • #2
I think that what you get is the projected rotation velocity, V_rot *sin(i) .
 

What is a galaxy rotation curve?

A galaxy rotation curve is a graph that shows how the rotational velocity of stars and gas within a galaxy changes with distance from the center of the galaxy. It is an important tool for understanding the dynamics of galaxies and the distribution of mass within them.

How is the angle of rotation related to the velocity and shape of the galaxy?

The angle of rotation is directly related to the velocity of the galaxy, as the larger the angle, the faster the rotational velocity. However, the angle does not have a significant impact on the overall shape of the galaxy rotation curve, which is primarily determined by the distribution of mass within the galaxy.

What factors can affect the shape of a galaxy rotation curve?

The shape of a galaxy rotation curve can be affected by the distribution of mass within the galaxy, including the presence of dark matter, as well as the distance from the center of the galaxy. The type and amount of gas present in the galaxy can also play a role in shaping the rotation curve.

How do scientists measure galaxy rotation curves?

Scientists measure galaxy rotation curves by observing the Doppler shift of light from stars and gas in the galaxy. This shift in wavelength can be used to calculate the rotational velocity of the galaxy at different distances from the center.

What can galaxy rotation curves tell us about the structure and evolution of galaxies?

Galaxy rotation curves can provide valuable information about the distribution of mass within a galaxy, including the presence of dark matter. They also help scientists understand the dynamics of galaxy formation and evolution, as well as the role of gas in shaping the structure of galaxies.

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