How to Calculate Rotation Curves for a Spiral Galaxy?

In summary, the individual is seeking help with calculating rotation curves for a spiral galaxy. They have a brightness profile and observed rotation curve, but need to find the total mass which requires surface mass density. They are unsure how to convert the brightness profile to mass density and are asking for assistance and references to help with this process. They also mention needing to assume a mass to light ratio but are unsure of the specific method for doing so.
  • #1
zaq
2
0
I hope this is in the right forum.
I'm trying to see how to calculate rotation curves for a spiral galaxy.
The data I have is brightness profile (mag/arcsec^2) and observed rotation curve - to see how it fits.
from what I found I need the total mass, and for that I need the surface mass density.
I couldn't find how to convert the brightness profile to mass density.
I can probably let MATLAB integrate the spline of the brightness profile, but that's not the mass density, so it wouldn't give me the mass I need.

Would appreciate help.
References to books (preferably with solved exercises) or other material are very welcome.

zaq
 
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  • #3
no, but thanks for trying.
I think I need to clarify what I'm asking.
The steps I found for calculating an RC are:
get the intensity profile
use that to find the mass distribution
use mass distribution to find g
calculate rotation curve.

I have the luminosity profile. (\mu). The units are mag/pc^2.
I need to convert it to mass distribution \SIGMA r (M/ pc^2).
how do I do that? I know I'm suppose to assume mass to light ratio but how exactly?
 

Related to How to Calculate Rotation Curves for a Spiral Galaxy?

1. How do you calculate a rotation curve?

To calculate a rotation curve, you need to use the formula v = √(GM/r), where v is the velocity of the object in question, G is the gravitational constant, M is the mass of the central object, and r is the distance from the center of the object.

2. What data is needed to calculate a rotation curve?

To calculate a rotation curve, you will need measurements of the velocity of the object at different distances from the center, as well as the mass of the central object. This data can be obtained through observations or simulations.

3. Why is calculating a rotation curve important in astronomy?

Calculating a rotation curve allows us to determine the distribution of mass in a galaxy or other astronomical object. This can help us understand the structure and dynamics of the object, as well as provide evidence for the existence of dark matter.

4. Can a rotation curve be used to determine the age of a galaxy?

No, a rotation curve cannot be used to determine the age of a galaxy. The rotation curve only tells us about the current distribution of mass in a galaxy, not its history.

5. How does the presence of dark matter affect a rotation curve?

The presence of dark matter can significantly affect a rotation curve. Dark matter has a gravitational pull, which can contribute to the overall mass of a galaxy. This can result in a flatter rotation curve, indicating the presence of more mass at larger distances from the center of the galaxy.

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