24 - Galaxy evolution

What can we hypothesise about high-redshift galaxies?

Galaxies should be fewer and smaller; denser universe means radioactive cooling is easier so galaxies should be forming stars faster; early galaxies must be younger; younger, more star-forming galaxies should be bluer; smaller bluer galaxies tend to be spirals/irregulars.

Early galaxies are ______ and _______ (quantity, size).

Fewer, smaller

Early galaxies are _______, _____, ____ ________ (age, colour, property)

Younger, bluer, star-forming

Early galaxies are more _____ and ________ (shape).

Spirals, irregulars

____’s increased sensitivity shows that many previous “irregulars” and “ellilpticals” actually have very faint _____ ____.

JWST, spiral arms

What conditions must a galaxy have for disks to re-grow following a merger?

Gas-rich

Which graph illustrates cosmic star formation rate density as a function of redshift, showing that the rate of star formation has changed over time, rising and falling?

Madau plot

Why does the madau plot rise and fall specificially?

The universe starts to accelerate, meaning that stuff is moving apart faster, thus less star formation; massive galaxies start to form into quenched ellipticals

What is quenching?

The process of star formation ceasing

To detect the initial stars and galaxies, High _________ and _________ are required.

Sensitivity, infrared

When the first galaxies formed, the young stars put out lots of UV light that re-ionized the universe. What did this lead to?

The Epoch of Reionization

What did JWST’s detections lead to (discovery)?

Galaxies seem to form earlier and brighter than we thought