How Does Angular Radius Relate to Deflection Angle in Redshift Calculations?

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Homework Help Overview

The discussion revolves around the relationship between angular radius and deflection angle in the context of redshift calculations, particularly in gravitational lensing scenarios.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants are attempting to connect various equations related to angular radius and deflection angle, while questioning how the provided data fits into these relationships. There are repeated inquiries about the distance to the lensed galaxy and its relevance to calculating the deflection angle.

Discussion Status

There is an ongoing exploration of the connections between redshift, distance, and deflection angle. Some participants are seeking clarification on their calculations and whether they are using the correct approach, but no consensus has been reached yet.

Contextual Notes

Participants are considering the implications of using redshift and Hubble's constant to calculate distances, which may influence their understanding of the deflection angle in this context.

stuartgriffin
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Homework Statement
A galaxy cluster of mass 3.0 × 1013M⊙ with known distance of 20 Mpc is observed in the centre of a bright ring, which is presumably a lensed galaxy. The angular radius of the ring from the cluster is 1.13 arcmin. The ring is observed to have a redshift of 0.0075. Assuming a value of 70kms−1Mpc−1 for the Hubble constant, determine whether the ring’s redshift distance is consistent at an accuracy of ~5% to the distance expected for the lensed galaxy to actually be located directly behind the cluster.
Relevant Equations
a=4GM/bc^2
V=H0D
I have attempted to link the equations, but I don't really understand how the data given fits. Does the angular radius get plugged in as the deflection angle?
 
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What is the distance to the lensed galaxy? How can this help you get the deflection angle?
 
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Orodruin said:
What is the distance to the lensed galaxy? How can this help you get the deflection angle?

Ahhh, thank you, so I calculate the distance using the redshift and hubbles constant? Am I on the right lines with the equations I am using?
 
Orodruin said:
What is the distance to the lensed galaxy? How can this help you get the deflection angle?
Does this look like I'm headed on the right track?
 

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