How do we determine the amount of dark matter in elliptical galaxies?

Answer 1

Astronomers look at the size and amount of visible material. They then figure out how much gravity it takes to hold the galaxy together, always greater than the observed mass, and attribute the rest to dark matter.

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Answer 2

Olivia Aldridge

Elliptical galaxies have a mass that can be inferred from the difference between the total mass of the galaxy and the mass that can be explained by visible matter alone. The amount of dark matter in these galaxies is found by measuring the velocity dispersion of the galaxy and the distribution of its visible matter.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.