Date post: | 28-Mar-2015 |
Category: |
Documents |
Upload: | melissa-malone |
View: | 221 times |
Download: | 1 times |
Cosmology and extragalactic astronomy
Mat Page
Mullard Space Science Lab, UCL
Revision Lecture
Recap of everything!• Galaxies:
– Classification+Structure– Dark Matter
• Hubble’s law– redshift and distance indicators
• Cosmological Principles, Olbers’s Paradox
• Cosmic microwave background– results and implications
• Inflation
• Nucleosynthesis, baryogenesis
Galaxies and dark matter
• Hubble’s tuning fork diagram
• Spirals + barred spirals– Sa: large bulge, tight arms. – Sc: small bulge, loose arms
• Star formation, gas and dust in arms
• Density wave model
• Rotation, rotation curve -> dark matter
• MACHOs, WIMPs, how they are detected
• 109-1011 Mo
Galaxies and dark matter
• Ellipticals
• E0-E7, En where n=10(1-b/a)
• Classified according to view from Earth
• Old, red stars (no star formation)
• little gas, little dust
• 105-1013 Mo
• Lenticulars (S0)– like spirals but no arms, just disc
• Irregulars– tend to be small, no definite structure
Where are the galaxies and how did they form?
– Galaxies form in dark matter haloes– Most of the galaxies in rich clusters are
ellipticals– bottom up vs. top down– hierarchical model - ellipticals built up by
merging of disc galaxies– spirals created when galaxies accrete gas (with
angular momentum) from the intergalactic medium
• Massive accreting black holes in galactic nuclei.
• 90% are radio quiet, but can be identified by their strong emission lines.
• Most quasars are seen at large redshifts (z>0.3)
Quasars
Hubble’s law
Hubble’s law
Cosmic distance ladder
Cosmic microwave background:
Inflation
• What is it?– A period of rapid expansion in the early
Universe– Caused by a state change as the Universe cools
• Why do we need it?– The horizon problem– large scale structure– flatness– the monopole problem
Olbers’s paradox
• Night sky should be infinitely bright!• Solution:
– The Universe is only 14 billion years old!– Light from stars more distant than 14 billion light
years has not have reached us yet.– There is a limit to the size of the Universe which can
illuminate the night sky.– The sky is allowed to be dark.
Finally:
• Good luck to you all!