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7

At a distance of $d = 87\,\mathrm{Mpc}$, with a Hubble constant of roughly $H_0 = 70\,\mathrm{km}\,\mathrm{s}^{-1}\,\mathrm{Mpc}^{-1}$ cosmological expansion should make the host galaxy UGC 11723 recede at $v=H_0 \,d\simeq6100 \,\mathrm{km}\,\mathrm{s}^{-1}$. However, galaxies also move through space, at typical velocities from several \$100\,\mathrm{km}\,\...

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A big picture reason is: because it's not really clear if it's scientifically sound to include multiple sources of data obtained from different methods. Astronomical measurements are very difficult, with huge numbers of confounding factors involved. Distance measurements are notoriously difficult because we can't actually measure interstellar distances ...

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The (late time) ISW is caused by the evolution of cosmic structures as photons of the cosmic microwave background traverse them on their way to our detectors. It may cause a redshift or blueshift with respect to the redshift predicted for a homogeneous expanding universe. A bit more detail: If a photon "falls" into a potential well, its frequency and energy ...

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There's only one kind of redshift in general relativity. The cosmological redshift, gravitational redshift, and special-relativistic redshift formulas are special cases of it, which apply to spacetimes with certain symmetries. If you put approximate Minkowski coordinates on a patch of spacetime that's small enough to be approximately flat, you'll find that ...

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