4 About Me…..‘Postdoc’ in the Astrophysics group at Bristol working with Professor Mark Birkinshaw, world expert in our fieldPrimarily research, some teachingPlus OutreachVarious projects, OCRA, AMiBAPreviously – PhD in Cambridge, working on the VSAMSci 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 effectThe experiments that I am working on
6 Before we go any further…. some things you need to know.
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 sunStars: stellar composition, stellar evolution, star formation, supernovae, extra-solar planetsGalaxies: structure, properties, stellar velocities (dark matter), formation, evolution, clustering…Active galaxies: mechanisms, power sources (black holes)High-energy phenomena: Gamma ray burstsGalaxy clusters: galaxy properties, gas properties, lensing (dark matter), super clustering….Large scale structure, structure formation theoriesCosmology: properties of the Universe as a whole, formation (the Big Bang), fate??
13 StarsStarsPlanetsPlanetsDISTANCE FROM USREDSHIFTAGNGalaxiesGalaxiesGalaxiesGalaxiesAGNClustersClustersClustersClustersClustersClustersCMBCMB
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.’
17 Obtain dataGo to telescopeDownload from archiveProcess dataWork out what it tells us!Publish in journal
18 In practice, need 2 approaches OBSERVATIONALObserve celestial bodies (stars, galaxies etc) at various wavelengthsFit theoretical models to data to choose the most appropriateTHEORETICALSimulate 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 scienceTenerife, Poland, Hawaii, Taiwan…..Very hot topics inAstrophysicsat 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 glowTurn up the resolution......
25 The ‘heat’ from the Big Bang varies across the sky The differences can be observed by sensitive telescopesThe variations are the ‘imprints’ of the beginnings of galaxy formationObservations 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 CMBEg Galaxy Clusters
32 Galaxy Clusters: Contain lots of galaxies (made from stars) Contain Dark MatterContain lots of GASGas is thought to be made of similar ‘stuff’ the the Universe as a wholeClusters 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 clustersThe ‘Sunyaev Zel’dovich (SZ) Effect’
34 SZ Effect: Sounds complicated! Cluster gas makes partial ‘shadow’ in the CMBINDEPENDENT of the distance of the clusterDepends ONLY on cluster characteristicsMeasure strength of shadow, learn about cluster (and Universe)
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 differExtrapolate (wildly?) between the two to understand how they are evolvingEVOLUTION OF THE UNIVERSE: Count the number of clusters at a great distance, compare with the number of clusters close to earthExtrapolate (even more wildly?) to understand how the Universe itself is evolving
38 My WorkI previously worked with the Very Small Array, looking at both the CMB and the SZ effectI am now involved with two new SZ experiments, OCRA and AMiBAWe are:Studying known clustersPerforming 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, Poland32m dishSuffers from atmospheric contaminationMost useful observations are made in the winterWill be able to IMAGE clusters in SZ for the first time
41 AMiBA - Array for Microwave Background Anisotropy Taiwanese project, based in Hawaii6m table, currently 7 ‘telescopes’Excellent for performing SURVEYSProblems 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 signalRequire further information, or observations at multiple frequencies.Remember the fluctuations in the CMB itself? They can also contaminate!Go to higher resolution
43 SummaryThe Big Bang left behind radiation which we can observe at radio frequencies todayThe Cosmic Microwave BackgroundThe 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 wholeGalaxy clusters may create ‘shadows’ in the CMBThe Sunyaev Zel’dovich EffectThe SZ effect is distance-independent so very useful for cluster physics and also Cosmology
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