Early CMB anisotropy measurements Rod Davies Jodrell Bank Centre for Astrophysics The University of Manchester

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1 Early CMB anisotropy measurements Rod Davies Jodrell Bank Centre for Astrophysics The University of Manchester Anthony Lasenby came into the CMB field at an exciting time. The 3K radiation had been decisively detected. The 3 mk dipole was also well-defined. The anisotropy search was at its most active. Sea-level sites were found to be inadequate and accordingly mountain sites with low water vapour levels were at a premium. After preliminary observations at Jodrell Bank the Manchester University team chose to collaborate with the Instituto de Astrofisica de Canarias at the Izana site on Tenerife for their successful beam-switch and interferometric searches. They were later joined by the Cambridge group in the Very Small Array project which obtained one of the earliest convincing power spectra of CMB fluctuations. Anthony had a pivotal role in the data analysis and the interpretation of these various projects. This has led to his substantial involvement in the Planck satellite which is the foremost CMB experiment. Early CMB ANL 1

2 The microwave dipole directed towards the Virgo cluster at a net velocity of 300 km/s relative to the Sun 600 km/s relative to the local Group (Andromeda and the Milky Way). The dipole amplitude is 3milliKelvin in the 3K CMB as seen from the Earth via a U2 plane and spacecraft in the late 1970s. The above is from COBE in Early CMB ANL 2

3 The Mark I and Mark II telescopes at Jodrell Bank. Early CMB ANL 3

4 The configuration of the beam-switch experiment with the Mark II telescope Lasenby & Davies (1983). The beam-width was 8 arcmin and the beam throw +/- 30 arcmin. Early CMB ANL 4

5 Upper limits from the 5 GHz Mark II experiment At 95% confidence upper limits, they ranged from 0.9mK at 10 arcmin to 1.5 mk at 40 arcmin. Amongst the lowest in 1982/3. Early CMB ANL 5

6 The 5 GHz interferometer at Jodrell Bank Early CMB ANL 6

7 Giardino et al m and 1.79m baselines shown separately. 5GHz 2-element interferometer at Jodrell Bank from 1990 to Dec = 30 to 55deg and 24 h in RA. Emission is dominated by point sources and the Galaxy. Early CMB ANL 7

8 The 10 GHz beam-switch system at Jodrell Bank in the exceptionally cold winter of 1983/4. Early CMB ANL 8

9 Choice of observing site Problems with atmospheric water vapour at sea-level sites. Seeing at altitude would take away tremors in the atmosphere Isaac Newton in his Opticks (1704). Piazzi Smyth demonstrated the truth of this proposal in his expedition to Tenerife in He made observations at Guahara (9000ft) and Alta Vista (10500ft). Note - Mt. Teide (12500ft) was too active. Piazzi Smyth made accurate beam-switch photometry of the Moon with a thermopile detector the first IR observations of a celestial object. The Jodrell beam-switch equipment was installed at the IAC IR telescope site at Izana Observatory (8000ft) in Our beam-switch was +/- 5 degrees compared with Smyth s +/- 20 degrees. Early CMB ANL 9

10 Izana Observatory, Tenerife 2400 metres Mt. Teide 3300 metres Early CMB ANL 10

11 Guahara site in the distance. The VSA Source Subtracter in foreground. Clouds beneath. Early CMB ANL 11

12 The Piazzi Smyth observatory at Alta Vista. His stereo-photography was pioneering. Note the tent behind and the stone slabs used as tables - plus Mrs. PS as recording assistant. Early CMB ANL 12

13 Gran Canaria in the distance. The inversion layer at 6000ft. Early CMB ANL 13

14 Sahara dust in east wind Early CMB ANL 14 -brilliant sunsets

15 he early team 1986 Early CMB ANL 15

16 Early CMB ANL 16

17 The 33 GHz interferometer Early CMB ANL 17

18 Bob and Diana. 33GHz interferometer Early CMB ANL 18

19 33 GHz interferometer sine and cos components at Dec = 41 O Harrison et al. (2000). Early CMB ANL 19

20 The status of CMB measures at the end of the 1990s (Harrison et al MNRAS 316, 24.) Early CMB ANL 20

21 The Cosmic Anisotropy Telescope MRAO Cambridge Early CMB ANL 21

22 CAT2 - Baker et al. (1990). deltat/t = 2.1 +/- 0.5 x 10-5 at l = 422. Dashed is estimate of Galactic emission. The frequencies are 13.5,15.5 and 16.5 GHz. Early CMB ANL 22

23 The GEM telescope in the background a temporary visitor. Early CMB ANL 23

24 The Role of Serendipity Be prepared for the unexpected! Penzias & Wilson in 1965 (ApJ ) discovered the CMB when testing a sensitive horn antenna at Bell Telephone s Holmdel site. In our case it was the discovery of a new radio emission mechanism when searching for the weak fluctuations in the CMB (the Anomalous Microwave Emmision AME). An excess emission was found both in compact regions and the diffuse Galactic environment. The emission is a maximum in the range GHz which is precisely the frequency range used in our search for the CMB. Bill Erickson had predicted such emission from small dust particles in The community thought that this emission was too weak to be of interest. We had to wait for Draine & Lazarian in 1998 to come up with a definitive theory only after emission from dust clouds had been detected! Early CMB ANL 24

25 A theory of dust radio emission Draine & Lazarian (1998) proposed that very small grains containing carbon atoms could be spun up to 10s of GHz frequencies in the ISM. Their likely electric dipole moments implied radio emission with a spectrum depending upon the conditions in the local ISM. Early observations covering the range 5 to 100 GHz showed that the spinning dust model could account for the data. There appeared to be a range of radio-to-dust emissivities. This was not unexpected since the observations covered different ISM environments. Early CMB ANL 25

26 The Perseus Molecular Cloud as seen at 1.2 o resolution the COSMOSOMAS beamwidth. Early CMB ANL 26

27 The Perseus Molecular Cloud close-up. The VSA (33GHz) resolution is ~7 arcmin( left hand image). The IRIS 100 micron image (right hand) is at the identical resolution. The VSA image has only 10% of the flux density of the COSMOSOMAS image - indicating diffuse AME emission throughout the region. 33 GHz 100 micron Early CMB ANL 27

28 Be prepared for the unexpected!! Early CMB ANL 28

29 The Very Small Array The VSA A collaboration between :-- Jodrell Bank The University of Manchester MRAO University of Cambridge IAC La Laguna, Tenerife Early CMB ANL 29

30 The installation of the VSA platform Early CMB ANL 30

31 Early CMB ANL 31

32 Early CMB ANL 32

33 Dickinson et al Early CMB ANL 33

34 In relaxation mode Early CMB ANL 34

35 The CBI at 16000ft on the Atacama Desert Early CMB ANL 35

36 Early CMB ANL 36

37 Plank Consortium meeting Izana Observatory, October 1997 The Plank proposal developed from the COBRAS concept we published in 1995 Early CMB ANL 37

38 Planck ready for launch Early CMB ANL 38

39 BON VOYAGE Early CMB ANL 39