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2. Angular Sizes of Galaxies Using HST, the Hubble Deep Field observation (two weeks of pointing at the same place on the sky!) reveals galaxies that range in redshift from $z = 0.2$ to $z = 4$ and in angular size from 0.1 to 5 arcseconds. Leave your answers to this problem in terms of the Hubble constant parameter $h$. (a) For each of the two cosmologies in problem 1, make plots of $\theta(z)$ (the angular size on the sky in arcseconds) for several choices of $l_{gal}$ (the proper physical size) in the range $l = 0.5$ kpc to $l = 10$ kpc (recall that one parsec is 3 light years). Discuss the relationship between angular size and proper size of the galaxies. How is this complicated by cosmology? (b) What measurements or other information about these galaxies would allow us to disentangle this ambiguity?

          2. Angular Sizes of Galaxies
Using HST, the Hubble Deep Field observation (two weeks of pointing at the same place on
the sky!) reveals galaxies that range in redshift from $z = 0.2$ to $z = 4$ and in angular size
from 0.1 to 5 arcseconds. Leave your answers to this problem in terms of the Hubble constant
parameter $h$.
(a) For each of the two cosmologies in problem 1, make plots of $\theta(z)$ (the angular size on the
sky in arcseconds) for several choices of $l_{gal}$ (the proper physical size) in the range $l = 0.5$
kpc to $l = 10$ kpc (recall that one parsec is 3 light years). Discuss the relationship between
angular size and proper size of the galaxies. How is this complicated by cosmology?
(b) What measurements or other information about these galaxies would allow us to disentangle this ambiguity?

2. Angular Sizes of Galaxies
Using HST, the Hubble Deep Field observation (two weeks of pointing at the same place on
the sky!) reveals galaxies that range in redshift from z = 0.2 to z = 4 and in angular size
from 0.1 to 5 arcseconds. Leave your answers to this problem in terms of the Hubble constant
parameter h.
(a) For each of the two cosmologies in problem 1, make plots of θ(z) (the angular size on the
sky in arcseconds) for several choices of lgal (the proper physical size) in the range l = 0.5
kpc to l = 10 kpc (recall that one parsec is 3 light years). Discuss the relationship between
angular size and proper size of the galaxies. How is this complicated by cosmology?
(b) What measurements or other information about these galaxies would allow us to disentangle this ambiguity?

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