17 - Redshift Surveys

We an measure the recession velocity using ________.

Redshifts

Galaxy light is composed of the cumulative light from all its ____, _______ ___, and _____ black holes.

Stars, shining gas, active

Shining gas emits ______ _____.

Emission lines

What do emission lines correspond to?

Specific atomic transition of hot gas

What do absorption lines correspond to?

Specific atomic transition of cool outer parts of stars

What can emission and absorption lines be used for?

Markers to measure redshift

How to do a redshift survey?

Map a region of the sky, take a spectrum for each galaxy, identify known features, then make a 3-D catalog

Why is distance from hubble’s law approximate?

Peculiar velocities can vary significantly, and we have no way to correct for them.

What effect does peculiar velocities lead to?

Fingers of God

How are Fingers of God formed?

Dense regions have more gravity, making galaxies orbit faster, and have a higher peculiar velocity, broadening dense groups of galaxies in redshifts

When were the first redshift surveys?

1980s

What would happen if the universe had more matter?

More matter so more gravity so faster growth so more structure

What happens if dark energy was 0?

Structure can still grow early on before dark energy dominated

How would you measure the growth rate of large-scale structure since the CMB?

Measure galaxy clustering, measure strength of Fingers of God, and measure weak lensing