Mergers And Energetic Galaxies Flashcards
Why were galaxy interactions more common in the early universe?
Galaxies were closer then
Why can disruption trigger bursts if star formation?
Gas compressed by gravity field
What is a major merger?
In full on collisions galaxies can merge into a single large galaxy. As gas clouds collide
Where do we see most ellipticals?
In areas with most galaxies (evidence for mergers creating ellipticals)
What galaxies do mergers allegedly form?
Ellipticals
When do stars in ellipticals seemingly form?
All at once, in a burst event
Why are starburst galaxies extremely bright in infrared?
Due to high star formation and lots of dust
How long do starburst galaxies typically last?
A few million years, produce billions of stars in that time
What is the average life of a starburst galaxy star?
Short life and explode quickly
How do starburst galaxies end?
Shockwaves combine into super bubbles, accelerate to form a coherent wind that drives material out of galaxy
What percentage of galaxies show bright point like centres?
1%
Describe active galactic nuclei
•enormously bright, often outshine rest of galaxy across spectrum
•variable on short timescales( hours to day)
•brightest type called quasars
What are 10% of AGN accompanied by?
Jets of plasma flowing out and ending in lobes
How big are jets?
Comparable in size of whole galaxy and much larger than AGN
How fast are jets?
Extremely fast moving close to speed of light
Why are jets bright radio sources?
Synchrotron emission from electrons spinning around magnetic field
How big is the AGN central power source?
Light hours across( solar system sized)
What is AGN source?
•huge power from tiny region
•strong radiations at all wavelengths
•high speed jets
• must be supermassive black hole
Explain model for AGN and quasars
•accretion disc orbiting black hole
•material falls, orbits, heats from friction, emits
•high speed so high energy
When were quasars more common?
In past when star formation was at peak
