How to Calculate Rotation Curves for a Spiral Galaxy?

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SUMMARY

This discussion focuses on calculating rotation curves for spiral galaxies using brightness profiles and mass density. The user seeks to convert a luminosity profile measured in magnitudes per square parsec to a surface mass density in solar masses per square parsec. Key steps outlined include obtaining the intensity profile, determining mass distribution, calculating gravitational acceleration, and ultimately deriving the rotation curve. The user specifically requests guidance on assuming a mass-to-light ratio for this conversion.

PREREQUISITES
  • Understanding of luminosity profiles in astrophysics
  • Familiarity with surface mass density calculations
  • Proficiency in MATLAB for numerical integration
  • Knowledge of mass-to-light ratio assumptions in galaxy studies
NEXT STEPS
  • Research methods for converting luminosity profiles to mass density, focusing on mass-to-light ratio assumptions
  • Learn about gravitational acceleration calculations from mass distributions in astrophysics
  • Explore MATLAB techniques for integrating spline functions related to brightness profiles
  • Study existing literature on galaxy rotation curves, including textbooks with solved exercises
USEFUL FOR

Astronomers, astrophysicists, and students studying galaxy dynamics who are interested in calculating rotation curves and understanding mass distribution in spiral galaxies.

zaq
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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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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?
 

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