1. An insight into the life of a Cosmologist
Katy Lancaster

2. About Me (Past)…..

3. About Me (Present)…..

4. About Me…..
‘Postdoc’ in the Astrophysics group at Bristol working with Professor Mark Birkinshaw, world expert in our field
Primarily research, some teaching
Plus Outreach
Various projects, OCRA, AMiBA
Previously – PhD in Cambridge, working on the VSA
MSci in Bristol (many moons ago!)

5. Talk Structure:
Some key concepts in astrophysics, and what we spend our time doing!
The Cosmic Microwave Background (relic radiation from the Big Bang)
Galaxy clusters and the Sunyaev Zel’dovich effect
The experiments that I am working on

6. Before we go any further…. some things you need to know.

7. STAR / PLANET

8. GALAXY
You are here!

9. THESE OBJECTS ARE THE FOCUS OF
GALAXY CLUSTER
THESE OBJECTS ARE THE FOCUS OF
MY CURRENT WORK

10. The Cosmic Web

11. Astrophysics: ‘That branch of astronomy which treats of the physical or chemical properties of the celestial bodies. Hence astrophysicist, a student of astronomical physics.’

12. Topics in Astrophysics…..
Solar System: planets, the sun
Stars: stellar composition, stellar evolution, star formation, supernovae, extra-solar planets
Galaxies: structure, properties, stellar velocities (dark matter), formation, evolution, clustering…
Active galaxies: mechanisms, power sources (black holes)
High-energy phenomena: Gamma ray bursts
Galaxy clusters: galaxy properties, gas properties, lensing (dark matter), super clustering….
Large scale structure, structure formation theories
Cosmology: properties of the Universe as a whole, formation (the Big Bang), fate??

13. Stars
Stars
Planets
Planets
DISTANCE FROM US
REDSHIFT
AGN
Galaxies
Galaxies
Galaxies
Galaxies
AGN
Clusters
Clusters
Clusters
Clusters
Clusters
Clusters
CMB
CMB

14. Cosmology: ‘The science or theory of the Universe as an ordered whole, and of the general laws which govern it. Also, a particular account or system of the universe and its laws.’

15. What do you astronomers
actually DO?

17. Obtain data
Go to telescope
Download from archive
Process data
Work out what it tells us!
Publish in journal

18. In practice, need 2 approaches
OBSERVATIONAL
Observe celestial bodies (stars, galaxies etc) at various wavelengths
Fit theoretical models to data to choose the most appropriate
THEORETICAL
Simulate celestial bodies (stellar evolution, galaxy formation etc)
Create models of possible physical processes

20. My Work: Very hot topics in Astrophysics at the moment!
COSMOLOGY from:
The ‘Cosmic Microwave Background Radiation (CMB)’
The interaction of the CMB with ‘Galaxy Clusters’ via the ‘Sunyaev Zel’dovich Effect’
OBSERVATIONAL - ie obtaining data, data processing, extracting science
Tenerife, Poland, Hawaii, Taiwan…..
Very hot topics in
Astrophysics
at the moment!

21. The ‘Cosmic Microwave Background Radiation (CMB)’
The Universe started with the ‘Big Bang’, a very hot explosion Hot things glow (candle, light bulb) in the optical or infra-red We can still see the ‘glow’ today Universe cooled - glow is in radio waves

22. Visualising the CMB…..
The sky is BRIGHT at radio frequencies. If we observe the sky with a radio telescope, inbetween the stars and galaxies, it is NOT DARK.

23. Observe ‘blank’ sky with a radio telescope.
Rather than darkness, see Uniform, high-energy glow
Turn up the resolution......

25. The ‘heat’ from the Big Bang varies across the sky
The differences can be observed by sensitive telescopes
The variations are the ‘imprints’ of the beginnings of galaxy formation
Observations of these features give us a lot of information about the nature of the Universe

26. Observing the CMB: COBE
Low resolution - tells us about the amount of ‘stuff’ in the Universe

27. A plethora of other experiments followed this up….until….

28. Observing the CMB: WMAP
High resolution - tells us about the TYPE of ‘stuff’ in the Universe (normal matter, dark matter)

29. More ‘features’ in the CMB
Let’s forget those tiny temperature variations for now!
Astronomical objects may cause ‘shadows’ in the glow from the CMB
Eg Galaxy Clusters

30. Galaxy cluster in OPTICAL light

31. Galaxy cluster in XRAY light

32. Galaxy Clusters: Contain lots of galaxies (made from stars)
Contain Dark Matter
Contain lots of GAS
Gas is thought to be made of similar ‘stuff’ the the Universe as a whole
Clusters are ‘Cosmic Laboratories’
Study clusters, study the Universe

33. Sunyaev and Zel’dovich, 1969
Postulated that the CMB could interact with the gas in galaxy clusters
The ‘Sunyaev Zel’dovich (SZ) Effect’

34. SZ Effect: Sounds complicated!
Cluster gas makes partial ‘shadow’ in the CMB
INDEPENDENT of the distance of the cluster
Depends ONLY on cluster characteristics
Measure strength of shadow, learn about cluster (and Universe)

35. What does it look like?
Very Small
Array

36. To study Cosmology via clusters, we need lots of them The SZ effect allows us to find ‘all’ clusters in existence Hot topic - surveying the sky at radio frequencies to find clusters

37. What will we learn?
CLUSTER EVOLUTION: Study clusters near and far and see how they differ
Extrapolate (wildly?) between the two to understand how they are evolving
EVOLUTION OF THE UNIVERSE: Count the number of clusters at a great distance, compare with the number of clusters close to earth
Extrapolate (even more wildly?) to understand how the Universe itself is evolving

38. My Work
I previously worked with the Very Small Array, looking at both the CMB and the SZ effect
I am now involved with two new SZ experiments, OCRA and AMiBA
We are:
Studying known clusters
Performing surveys to find new ones

39. Wot no satellite? Going to space is EXPENSIVE!
Choose your frequency wisely, can achieve a lot from the ground (sometimes before NASA / ESA have even launched their satellite!)

40. OCRA - One Centimetre Receiver Array
New detector on Torun telescope, Poland
32m dish
Suffers from atmospheric contamination
Most useful observations are made in the winter
Will be able to IMAGE clusters in SZ for the first time

41. AMiBA - Array for Microwave Background Anisotropy
Taiwanese project, based in Hawaii
6m table, currently 7 ‘telescopes’
Excellent for performing SURVEYS
Problems with the platform - not strong enough!

42. Challenges…. The SZ effect is TINY The radio sky is bright
Galaxy clusters contain galaxies (!), which may emit radio waves and drown the SZ signal
Require further information, or observations at multiple frequencies.
Remember the fluctuations in the CMB itself? They can also contaminate!
Go to higher resolution

43. Summary
The Big Bang left behind radiation which we can observe at radio frequencies today
The Cosmic Microwave Background
The CMB has imprints upon it caused by the formation of the structures we see today (eg galaxies)
The CMB tells us much about the Universe as a whole
Galaxy clusters may create ‘shadows’ in the CMB
The Sunyaev Zel’dovich Effect
The SZ effect is distance-independent so very useful for cluster physics and also Cosmology

44. ANY QUESTIONS?