For two objects at a redshift $z$, I know that the proper distance between them is given by $\delta \theta d_M(z)$, where $d_M(z)$ is the transverse comoving distance. What are the units of the angle out front? I know that $d_M$ has units of Mpc, but should the $\delta \theta$ be in degrees, radians, etc? And why is that the case?


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