PHYSICS 20B Lecture Notes - Lecture 25: Puffy Amiyumi, Active Galactic Nucleus, 3C 48
9 Jun 2018
School
Department
Course
Professor
PHYSICS 20B - Lecture 25 - Life Cycle of Galaxies
Big galaxies in the local universe come in 2 basic types
Rotating disks
- Usually blue and forming stars
Balls of random motion
- Usually red and not forming many stars
●Big galaxies (more than ~ stars) (as long as Milky Way or larger) tend to be either01 10
spiral or elliptical
●Smaller galaxies today tend to be neither, instead “irregular”
●Irregular galaxies are “puffy”, rotating and messy
○Tend to be forming stars and blue
●Keep in mind that spiral vs. elliptical classification is broad, there is still quite a bit of
variety even within these two classes. Differences have to do with the unique way each
galaxy formed
Most galaxies in early universe are blue and star forming
●Why are the big galaxies today mostly done forming stars?
●What shut down star formation?
○Galaxy merges may have played a role
○Mergers and disks can build ellipticals
Document Summary
Physics 20b - lecture 25 - life cycle of galaxies. Big galaxies in the local universe come in 2 basic types. Usually red and not forming many stars. 01 10 stars) (as long as milky way or larger) tend to be either spiral or elliptical. Smaller galaxies today tend to be neither, instead irregular . Irregular galaxies are puffy , rotating and messy. Tend to be forming stars and blue. Keep in mind that spiral vs. elliptical classification is broad, there is still quite a bit of variety even within these two classes. Differences have to do with the unique way each galaxy formed. Most galaxies in early universe are blue and star forming. Galaxy merges may have played a role. In the 1950s, radio astronomers started compiling lists of radio sources in the sky. Many were identified with distant galaxies, but some had no visible optical counterpart. Two strong radio sources ( 3c 48 and 3c 273 were weird.
