A How to convert between different mass measurements for CDM H

AI Thread Summary
To convert cluster mass from M_500c to M_200c, understanding the relationship between these measurements is crucial, as M_500c represents mass within R_500 and M_200c within R_200, with R_500 being approximately 0.7 R_200. The NFW profile can assist in this conversion, but it may be simpler to adjust the mass-velocity dispersion relationship to M_500c instead. However, some users prefer to adhere to specific methodologies from existing papers for consistency in their results. Resources that explain these mass definitions can provide additional clarity. Ultimately, the conversion process is essential for accurately relating cluster mass to velocity dispersion.
floyd0117
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If I have a cluster with a mass measured in M_500c, then how do I go about converting that mass to M_200c given some concentration and an NFW profile?
 
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What do you mean converting the mass? What are you converting? Why?
 
Chalnoth said:
What do you mean converting the mass? What are you converting? Why?

I have a dataset of cluster masses, expressed in units of M_500c, which I need to relate to a velocity dispersion. But the relation between cluster mass and velocity dispersion is in terms of M_200c, so I need to convert the masses in the dataset before I can find the equivalent dispersions.
 
floyd0117 said:
I have a dataset of cluster masses, expressed in units of M_500c, which I need to relate to a velocity dispersion. But the relation between cluster mass and velocity dispersion is in terms of M_200c, so I need to convert the masses in the dataset before I can find the equivalent dispersions.
Ahh, okay. I'm honestly not sure. I did find this resource, which describes these measures a bit:
https://www.princeton.edu/astro/undergraduate/astro-jps-senior-theses-a/bilhudathesis-2.pdf

It looks like M_{500} is the mass within R_{500}, while M_{200} is the mass within R_{200}, where R_{500} \approx 0.7 R_{200}. If you've got a good understanding of the NFW profile, you might be able to use that to do the conversion.

That said, my guess is it'd be even better to convert the relation between mass and dispersion to be in terms of M_{500} instead of M_{200}, as that's most likely a far simpler operation.
 
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Chalnoth said:
Ahh, okay. I'm honestly not sure. I did find this resource, which describes these measures a bit:
https://www.princeton.edu/astro/undergraduate/astro-jps-senior-theses-a/bilhudathesis-2.pdf

It looks like M_{500} is the mass within R_{500}, while M_{200} is the mass within R_{200}, where R_{500} \approx 0.7 R_{200}. If you've got a good understanding of the NFW profile, you might be able to use that to do the conversion.

That said, my guess is it'd be even better to convert the relation between mass and dispersion to be in terms of M_{500} instead of M_{200}, as that's most likely a far simpler operation.

Perhaps, but I'm trying to follow the methodology presented in a specific paper and replicate their results. Thanks anyway
 
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floyd0117 said:
Perhaps, but I'm trying to follow the methodology presented in a specific paper and replicate their results. Thanks anyway
Makes sense. Sorry I can't be of more help.
 

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