Determining Distances to Galaxies

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Determining a galaxy's distance can be approached by estimating its actual size and using reverse triangulation, although this method is challenging. Standard candles like Cepheid variables and supernovae are commonly used for distance measurement, with SN 1987A providing a notable example. For galaxies outside the local group, redshift and Hubble's law offer a way to estimate distances. The rotation curve of a galaxy, derived from Doppler shifts, can also provide insights but is limited to galaxies that are edge-on. Overall, while multiple methods exist, each has its own constraints and complexities.
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Is there anyway to determine a galaxy's distance by figuring out its actual size (or the visual portion) and then reverse triangulate to us? All I hear is about standard candles as the source for determining galactic distances - either Cepheid variables or Supernovae.

We have of course reverse triangulated to the LMC using the famous SN 1987A shockwave. Reading about that made me wonder if we have other ways of independently determining the actual galaxy size. Perhaps we could use a galaxy's rotation curve to determine a distance? Or at least be able to compare similar galaxies and determine a relative distance.

Thanks!

sderamus
 
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For galaxies not in our local group, we can use redshift to estimate a distance (via, Hubble's law).

Uhm...trying to get the actual size of a galaxy is tough. You can try using doppler shifts on the edges to obtain a rotation curve, but that would require the galaxy to be relatively edge on...
 

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