^-space spectroscop Cosmie th f yo c Microwave Background wit BOOMERane hth G experiment P. de Bernardis1, RA.R. Ade2, JJ. Bock3, J.R. Bond4, J. Borrill5, A. Boscaleri6, K. Coble7, C.R. Contaldi4, B.R GrillGasperise D . Troia8e ,G D . 9Farese. ,G 1 ,P 7, K. Ganga Giacometti. 10,M Hivon. 1,E 10, V.V. Hristov lacoangel. 8,A i l A.H. Jaffe11, W.C. Jones8, A.E. Lange Martinis. 8,L 12Masi. ,S Mason. 1,P 8, P.O. Mauskopf Melchiorri. 13A , 14Natoli. ,P Montroy. 9,T 7, C.B. Netterfield15, E. Pascale6, E Piacentini1, D. Pogosyan4, G. Polenta1, E Pongetti16, S. Prunet4, G. Romeo16, I.E. Ruhl 7Scaramuzzi,E Vittorio. 12,N 14 1 Dipartimento Fisica,di Universitd Sapienza,La Roma, P.le Mow,A. 00185,2, Italy. 2 Queen Maryand Westfield College, London, UK. 3 Jet Propulsion Laboratory, Pasadena, CA, USA.4 C.I.T.A., University of Toronto, Canada.5 N.E.R.S.C., LBNL, Berkeley, CA, USA. 6IROE-CNR, Firenze, Italy.1 Dept. of Physics, Univ. of California, Santa Barbara, CA, USA. 8 California Institute of Technology, Pasadena, CA, USA. 9 Department of Physics, Second University of Rome, Italy. 10IPAC, Caltech, Pasadena, CA, USA. u Department of Astronomy, Space Sciences Centerand Particlefor Lab Astrophysics, University ofCA, Berkeley, 94720CA USA. u ENEA, Frascati, Italy. ° Dept. of Physics and Astronomy, Cardiff University, Cardiff CF24 3YB, Wales, UK. 14 Nuclear and Astrophysics Laboratory, University of Oxford, Keble Road, Oxford, OX3RH, UK.15 Depts. of Physics and Astronomy, University of Toronto, Canada.16 Istituto Nazionale di Geofisica, Roma, Italy. Abstract BOOMERane Th . G experimen recentls tha y produced detailed Cosmimape th f so c Microwave Back- ground, where sub-horizon structures are resolved with good signal to noise ratio. A power spectrum (spherical harmonics) analysis of the maps detects three peaks multipolet ,a (213~^\®),= st (541^32)5 (^^-25)' ^n ^s PaPer we discuss the data analysis and the implications of these results for cosmology. INTRODUCTION Cosmie Th c Microwave Background (CMB windoa Earls )e i th wyn o Universe comet .I s fro epocn ma he wheag e nth hundre Universw e ofe fth a s d thousanewa d years (50000 times younger than today) temperature ,th abous ewa t 3000 K (1000 times more tha nbillio e densit e todayon th s nd ytime)wa an s larger than today [1],[2] vere .yTh presencf eo compellina s i B densd CM g e an existencprooe t eth th initiaho f fo a f elo phasUniverse th n ei e [3], physice [4]Th . s photons-baryone ofth s plasma presen that a t t epoch interactios it , n wit underlyine hth g dark matter distributiond an , the resulting observable effects on the CMB have been studied in great detail [5]. If the inflationary scenario is true, photons coming from that epoch carry information which has been encoded at much earlier epochs, thus enabling us to investigate the history of the Universe as early as 10~36s after the Big-Bang. (processeda s i B AnCM imag)e imagth f eo quantuf eo m fluctuations presen Universe th n ti e befor inflatioe eth n phase [6], at energies of the order of the GUT energies. thin I s framework derivee statisticae b ,th n ca d ) fro 5 A l, B mTpropertie(a firsCM image e t th th principles f f seo o , given a small set of cosmological parameters. AT (a, 8), is expected to be a 2-D random gaussian field, with statis- 2 a tical properties fully describe powes it y db r spectrum Q. Here Q(\a^= m\ ), where A TZ^= (a ) ,w8 ^,m^( '$)- Analyzing the image and its power spectrum, it is then possible to estimate the cosmological parameters [7]. Many experimental teams have actively worke measuremene th n do spectrume th f anisotrope o tth f o , y power polarizatioe spectruth f o CMB e d th purelme an f no .Th y Planckian naturspectrue th f eo bees mha n establishey db CP616, Experimental Cosmology at Millimetre Wavelengths, 2K1BC Workshop, edited by M. De Petris and M. Gervasi © 2002 American Institute of Physics 0-7354-0062-8/02/$ 19.00 3 Downloaded 02 Oct 2007 to 131.215.225.176. Redistribution subject to AIP license or copyright, see http://proceedings.aip.org/proceedings/cpcr.jsp the FIRAS spectrometer on board of the COBE satellite [8]. It is the proof of the cosmological nature of the CMB and of the Hot Big Bang theory proposed by Gamow in the 50s. The intrinsic, faint large scale anisotropy has been first detected by the DMR instrument on board of the COBE satellite [9]. Its low level and its power spectrum supported the inflationary hypothesis [6]. The degree and sub-degree-scale anisotropy has been detected by several ground based and balloon-borne experiments. Only recently, however, it has been possible to first detect the presence of peaks in the power spectrum [10], [11] produc,o t [12] d an , e images wher sub-degree eth e anisotrop clearls yi y visible [13], [14], [15], [16] presence Th . multiplf eo e peakconfirmatioe th s si presence th f no acoustif eo c oscillation plasme th n si a before recombination [5] and allows the detection of several important cosmological parameters [17], [18], [33]. In this pape repore w r t results fro BOOMERane mth G experiment balloon-borna , e microwave telescope with cryogenic bolometric detectors. Several aspect instrumene th f so othed tan r result describee sar companiodn i n papers in this same conference proceedings [19], [20], [21], [22], [23], [24]: heranalysi e focue th e w n so s techniquen o d san the cosmological significance of the results. ^-SPACE SPECTROSCOPY detectiodifficule a s i Th B tf structure no experimenta CM e th n si l problem observable sizth e f eTh o . e temperature fluctuations is of the order of a few tens pK, while instrumental, local and astrophysical backgrounds can be as large differencee Th . K spectraw an si sfe angulad lan r distributions allo experimentaliste wth separato st cosmologicae eth l component fro contaminationse mth elaboratt ,bu e modulation technique needee sar d [25], [19],[26]. Interferometers directly sample the correlation function of the temperature fluctuations [27], while total power receivers sample the temperature map powee :th r spectru mderives i firsy db t organizin time-orderee gth d theobservationd an n p ma a n si performin harmonie gth c analysis. case I nBOOMERanth f eo G modulatio achievens i constan t scannina y d b y sk e tg elevatioth constand nan t azimuth speed. The signal from the detector is AC coupled and high pass filtered. Since most of the contaminating signals are either constant or smooth in the sky, they are efficiently rejected by this modulation. The disadvantage of this technique is that it results in an anisotropic filtering of the sky maps, which has to be taken properly in account in the data analysis (see below). A further level of modulation comes from sky rotation. In fact, the central azimuth of the azimuth scans tracks the azimut besregione y th sk tf ho , while elevatio t changeno s ni d durin onl s i scane gd th y an change, stepn di s every several hours resule Th .f thi o t s rotationstrategy sk o scant e thats yi th e graduall,e sar du , y skye d tilteth an , n di the same pixel will be re-observed during the same day in differently tilted scans. This produces significant cross- linking in the sky coverage, which is important for the map-making algorithm used to create the image of the sky. The same proces repeates si severar dfo l days comparisoe Th . mapf no s obtaine differenn di t days, whe payloae nth s dha drifted by thousands of km and the ground configuration is completely different, is a very effective tool to exclude contamination of the sky maps coming from the telescope sidelobes. The peak to peak length of our azimuth scans is M ^ 60°, so that the scans in the sky have a length A6 ~ AA cos e ~ 42°, This lengt bees hha n selecte bese th ts dcompromisa e between several factors coveragey sk : , avoidanc sune th ,f eo repetition frequency of scans, detector's speed, 1/f knee in detectors noise, etc. As a result, our £-space resolution is limited to A£ ~ n/ A6 ~ 4. This is more than enough to resolve the acoustic peaks present in the power spectrum of the CMB anisotropy, which hav widtea h Mp ^100 [5] practicen .I degrade ,w instrumentae eth l resolutio ~no t Alpy /2b binning in I, in order to improve the signal to noise ratio in each t bin. The estimates of the power spectrum averaged over wide t bins are called bandpowers. The finite length of the scans also limits the lowest multipole detectable tmin ~ A€, but in practice a much higher tmin ~ 25 is set by the presence of drifts and I// noise. The maximum multipole observabl constann ei t speed scans depend angulae th n so r resolutio telescopee th timf ne o th en respons,o e detectoe ofth noises it n generarn o ;i [28 d sensitivit]an e lth instrumene th f yo differeno tt t multipole describes si y db suitabla e window function taking into account these effects (see below) case BOOMERanf th eo n .I G tmax ~ 1200. 1998/9E DATB TH 9LD A The BOOMERanG payload was flown by NASA-NSBF on Dec.29,1998, from McMurdo (Antarctica).