the large scale structure of the universe
DESCRIPTION
The Large Scale Structure of the Universe. Clusters of galaxies X-rays from clusters of galaxies Sheets and voids. Our Galaxy is a member of a small cluster called the Local Group. Stephane’s Quintet. Virgo cluster. Abell 2218. Coma cluster. Virial Theorem. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: The Large Scale Structure of the Universe](https://reader036.vdocument.in/reader036/viewer/2022062321/568135d5550346895d9d416c/html5/thumbnails/1.jpg)
The Large Scale Structure of the Universe
• Clusters of galaxies
• X-rays from clusters of galaxies
• Sheets and voids
![Page 2: The Large Scale Structure of the Universe](https://reader036.vdocument.in/reader036/viewer/2022062321/568135d5550346895d9d416c/html5/thumbnails/2.jpg)
Our Galaxy is a member of a small cluster called the Local Group
![Page 3: The Large Scale Structure of the Universe](https://reader036.vdocument.in/reader036/viewer/2022062321/568135d5550346895d9d416c/html5/thumbnails/3.jpg)
Stephane’s Quintet
![Page 4: The Large Scale Structure of the Universe](https://reader036.vdocument.in/reader036/viewer/2022062321/568135d5550346895d9d416c/html5/thumbnails/4.jpg)
Virgo cluster
![Page 5: The Large Scale Structure of the Universe](https://reader036.vdocument.in/reader036/viewer/2022062321/568135d5550346895d9d416c/html5/thumbnails/5.jpg)
Abell 2218
![Page 6: The Large Scale Structure of the Universe](https://reader036.vdocument.in/reader036/viewer/2022062321/568135d5550346895d9d416c/html5/thumbnails/6.jpg)
Coma cluster
![Page 7: The Large Scale Structure of the Universe](https://reader036.vdocument.in/reader036/viewer/2022062321/568135d5550346895d9d416c/html5/thumbnails/7.jpg)
Virial Theorem
• For gravitationally bound system,
• Where K is kinetic energy and U is potential
• Check for planet orbiting star
02 UK
r
GMv
mvK
r
GMmU
2
2
02
222
r
GMm
r
GMm
r
GMmmvUK
![Page 8: The Large Scale Structure of the Universe](https://reader036.vdocument.in/reader036/viewer/2022062321/568135d5550346895d9d416c/html5/thumbnails/8.jpg)
For Cluster• Kinetic energy
• Where mi, vi are mass, velocity of each galaxy
and M, <v2> are total mass, average velocity
• How to find <v2>?• Can measure only line of sight velocity
• Note <v2> = <vx2 + vy2 + vz2> = 3 <vz2> = 32
where is the “velocity dispersion”
22
2
1
2
1vMvmK
iii
![Page 9: The Large Scale Structure of the Universe](https://reader036.vdocument.in/reader036/viewer/2022062321/568135d5550346895d9d416c/html5/thumbnails/9.jpg)
For Cluster• Kinetic energy• Potential energy
where rh = “half-light radius”
• Use virial theorem 2K+U = 0 to find
2
2
3 MK
hr
GMU
2
4.0
G
rM
r
GMM
h
h
2
22
5.7
04.02
32
![Page 10: The Large Scale Structure of the Universe](https://reader036.vdocument.in/reader036/viewer/2022062321/568135d5550346895d9d416c/html5/thumbnails/10.jpg)
For Coma Cluster
• rh = 1.5 Mpc
= 880 km/s
• Calculate M = 2×1015 M
• Note that this includes dark matter
• Mass to light ratio of cluster is 250 M/L
![Page 11: The Large Scale Structure of the Universe](https://reader036.vdocument.in/reader036/viewer/2022062321/568135d5550346895d9d416c/html5/thumbnails/11.jpg)
Coma cluster
in X-rays
![Page 12: The Large Scale Structure of the Universe](https://reader036.vdocument.in/reader036/viewer/2022062321/568135d5550346895d9d416c/html5/thumbnails/12.jpg)
Coma cluster• X-ray emitting gas is at 100,000,000 K.• The total X-ray luminosity is more than the
luminosity of 100 billion Suns.
• From this, the amount of X-ray emitting gas can be calculated to be 2×1014 M
• The mass of X-ray emitting gas is greater than the mass in all the stars in all the galaxies in the cluster and about 10% of the total mass.
![Page 13: The Large Scale Structure of the Universe](https://reader036.vdocument.in/reader036/viewer/2022062321/568135d5550346895d9d416c/html5/thumbnails/13.jpg)
Gravitational lens
![Page 14: The Large Scale Structure of the Universe](https://reader036.vdocument.in/reader036/viewer/2022062321/568135d5550346895d9d416c/html5/thumbnails/14.jpg)
Gravitational lenses
• By measuring multiple images of one source, we can figure out the total mass in the lens. This provides an independent confirmation of dark matter.
• A lense can act as a huge telescope. The deepest images of the most distant galaxies are obtained with clusters acting as gravitational lenses.
![Page 15: The Large Scale Structure of the Universe](https://reader036.vdocument.in/reader036/viewer/2022062321/568135d5550346895d9d416c/html5/thumbnails/15.jpg)
The red Galaxy is 13 billion light years away. We are seeing it 750 million years after the Big Bang.
![Page 16: The Large Scale Structure of the Universe](https://reader036.vdocument.in/reader036/viewer/2022062321/568135d5550346895d9d416c/html5/thumbnails/16.jpg)
Large Scale Structure
• Are clusters of galaxies the largest structures in the Universe?
![Page 17: The Large Scale Structure of the Universe](https://reader036.vdocument.in/reader036/viewer/2022062321/568135d5550346895d9d416c/html5/thumbnails/17.jpg)
Million galaxies
![Page 18: The Large Scale Structure of the Universe](https://reader036.vdocument.in/reader036/viewer/2022062321/568135d5550346895d9d416c/html5/thumbnails/18.jpg)
Redshift survey
![Page 19: The Large Scale Structure of the Universe](https://reader036.vdocument.in/reader036/viewer/2022062321/568135d5550346895d9d416c/html5/thumbnails/19.jpg)
Large Scale Structure
• Galaxies and clusters of galaxies are organized on irregular sheets separated by voids containing few galaxies.
• The density fluctuations seen in the cosmic microwave background are likely the seeds for the formation of the sheets, clusters, and galaxies.
• How that process occurs is now being worked out.
![Page 21: The Large Scale Structure of the Universe](https://reader036.vdocument.in/reader036/viewer/2022062321/568135d5550346895d9d416c/html5/thumbnails/21.jpg)
Review Questions
• How can we measure the mass of a cluster of galaxies?
• At what wavelength do galaxy clusters glow brightest?
• On the largest scales, how are galaxies arranged?