^-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 yth 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). It remained at floa r 10.fo t6 days, circumnavigating Antarctic averagn a t aa . Aboue altitud km millio 7 7 5 t3 f eo n 16-bit samplef so the signal were collected for each of the 16 detectors. The data were edited for known instrument glitches, temperature

Downloaded 02 Oct 2007 to 131.215.225.176. Redistribution subject to AIP license or copyright, see http://proceedings.aip.org/proceedings/cpcr.jsp fluctuations cosmid an , c rays events . bolometee Lesth f so tha% rn5 dats beeaha n founcontaminatede b o t d . Constrained realizations of noise were substituted to the contaminated signals. The pointing has been reconstructed from the signals of the laser gyroscopes, of the differential GPS, and of the sun sensors mose th tn .I recen t pointing solution, repeated observation compacf so t sources show tha accurace tth f yo reconstructioe th arcmi5 s n;i $ 2. n rms. Random errorpointine th n si g hav effece eth smear-ouo t t signale tth s from small sources. This adds in quadrature to the intrinsic angular resolution of the telescope (9.5' FWHM at 150 GHz). The finite size of the pixelization has a similar effect. In t space these three effects are modelled by the low pass filter W(f) shown in fig.l (called window function), which has to be taken into account in the reconstruction of the angular power spectrum of the sky. It is evident how these effects limit the sensitivity of our observations at high multipoles.

0,2 -

0,0 1000

FIGUR . E1 Windo w functio BOOMERanne th W(l) r fo G instrumen tgaussiar (B98fo d )an n beams with FWHM=9.5 13'd an '. The time-domain high-pass filter is not included in the window function of fig.l since its effect is, in general, anisotropic. It can be shown, however, that for our particular scan strategy the time-domain high pass filter acts as a high pas smultipolee filteth n i r s domain [29]. Sky maps have been constructed fro time mth e ordered datpointind aan g using four independent methods: naive maps (just coaddin samge datth en a o pixel) ; maximum likelihood maps obtained usin MADCAe gth P package ([30]); maximum likelihood maps obtained using the iterative method of [31]; suboptknal maps obtained using the fast map making metho [29]f do . All methods produce very similar maps. In fig. 2 we show the central region of the 150GHz map from the B150A channel obtained wit iterative hth e method [31]coloe Th . r cod eBOOMERane useth n di G maps correspono dt temperature fluctuation 2.73a f so K blackbody. Degree-scale structure GHz0 s15 wit t . a Consisten hp amplitud ma evidene jiK 0 e ar ordee 10 th th t f n f i o rteo structur GHz0 similarite alss ei 24 Th .od temperatur e evidenan th mape f 0 yo 9 th t sn a ti e maps obtaine different da t frequencie sbes e origidetecte[13e B th tth s ]evidenci f nCM o e d th fluctuations r efo . Foregrounds contamination nca be constrained significantly in the center of the observed sky region [13], [20].

THE POWER SPECTRUM

Netterfiel t alde . [15] have compute powee dth r spectru centrae th f mo l regioBOOMERane th f no G 150GHz maps (1.8sky) e resule th bees %f Th . o ha t n obtained wit monte-carlha o technique, which allow estimato st e effectively coverageeffecty e th sk f so , anisotropic filtering, system nois measure e bead th ean mn o d power spectrum [29]. Using about 10 times more data and about 80% more sky than the original data release, with an improved pointing solution

Downloaded 02 Oct 2007 to 131.215.225.176. Redistribution subject to AIP license or copyright, see http://proceedings.aip.org/proceedings/cpcr.jsp 2001-11-05 6.9 - LPfil' t = 0.15

-400 uK! 1400 uK -400 -200 200 400

_40

-45

-50

80 85 90 95 100 105 RA [Deg]

FIGURE 2. Map of the microwave sky measured by BOOMERanG at 150 GHz. The resolution of the observations is 12 arcmin. Healpix pixelization with 3.5' pixel side has been used. The units are for thermodynamic temperature fluctuations of a 2.73K blackbody. The same structures are visible in the 90 GHz and in the 240 GHz maps of BOOMERanG. and a better measurement of the effective beam, it was possible to detect three peaks in the power spectrum of the CMB (see fig.3). Bandpowers have been computed followin recipe gth [50]f eo . These dat comparee aar simultaneoue th do t s data releases of the DASI [32] and MAXIMA [33] teams in fig.4. Given the orthogonality of the experimental and analysis methods, the agreement of the three results is very good, at least visually existine .Th g anti-correlation bandpowerse th n si presence th d ,an som f eo coveragey overlask e th f epn o i the BOOMERanG and DASI data should be taken into account for a more quantitative comparison. Such a comparison will be the best argument to exclude significant systematic effects in the three spectra.

COSMOLOGY-INDEPENDENT DATA ANALYSIS

Let's consider firsproblee th t f massessino statisticae gth have w l epropertiey obtainesk image e th th f t f dsea o o 150 GHz. We are interested to see if the temperature of the CMB in the sky is distributed as a Gaussian. If this is true, then the power spectrum measures all the information encoded in the image. The gaussianity of the image is not a trivial result of the central limit theorem. As a matter of facts, images of the sky with the same resolution, but at higher frequencies, are highly non-gaussian. A visual exam of the IRAS maps of interstellar dust emission at 100 jim is very convincing in this regard [34]. In fig.5 we compare the 1-P distribution of the ISOGHz map (dominated

Downloaded 02 Oct 2007 to 131.215.225.176. Redistribution subject to AIP license or copyright, see http://proceedings.aip.org/proceedings/cpcr.jsp •fUUU i - i • i • i • i

6000 T BOOMERanG channel4 z 1t s a 5 0GH J* Y x^ 5000 _1 3. 4000

13000 5 s- 2000 : Ii"11 'llf-i^J 1000 - ...... ty n 200 400 600 800 1000 multipole

FIGURE 3. CMB anisotropy power spectrum detected by BOOMERanG. The dataset plotted as circles and the dataset plotted as square significantle sar y correlated bote ar hd plotte,an shodo t effece w th differen f o t t binnin €-spacegn i differene .Th t bandpowers same ofth e datase insteae tar d effectively uncorrelated beagaid e an nm.Th ) calibratio) (10 (1.410 10 %t t a a ' n plottedt errorno e sar , since the totalle yar y correlatebandpowerse th l al r dfo .

by CMB anisotropy) to the 1-point distribution of the same patch of the sky measured by BOOMERanG at 410 GHz (dominated by thermal emission of interstellar dust). Even this naive test shows that the CMB is something special, being very accurately gaussian distributed. Of course, for a more quantitative test of the 1-P distribution it is necessary to take into account the correlation properties of the signal and of the noise in the data. simplese Th t non-gaussianity estimator pixee th ln si spac Skewnese ear Kurtosid 1-poinse an th f so t distribution, Minkowske th d an i functionals. [35] have analyze ISOGHe dth z map BOOMERanf so G using these five estimators, and a Monte-Carlo approach to account for the correlations in the data, to compute the statistical significance of the result assesd san effece s th f systematics o t teste consistene th sar l Al . t wit gaussiae hth n hypothesis reportes a , n di table 1. Small non gaussian signals added to the gaussian CMB fluctuations can be excluded with different levels of significance, depending on the nature of the contaminants. For example the rms of fluctuations distributed as a 1 DOF % 2CMB e musth lesf e o tb . s Fluctuation tharm e n th 3instrumenta o %f t o e sdu l effects wels a ,fluctuation s la o t e sdu duse th t foregroun extragalactio t d dan c point source foun e irrelevante sb ar o dt . Spectral method studo st y gaussianity are also being exploited. Ther mane ear y kind non-gaussianitf so y throug a [36] d ,an h analysis wilf lo require us e eth many different methods. Given the results above, however, it is reasonable to assume that the power spectrum is the only tool we need to study the statistical properties of the image. [15] have discussed how the measured power spectrum of the sky is robust against variations of the l-binning, channel selection, data subset selection, effects of uncertainties in the beam and effects of the noise. [17] have shown that the three peaks and two dips present in the power spectrum are statistically significant. The first peak is at t\ = (213+13) (the errors correspond to a 10 confidence interval in the location if the peak) amplituds .It detectes ei , whil t d>a 50 , e fosecone rth d pea 4 t (541JI^)k= (a third )dan pea €t 3(845^25)k= (a ) the amplitudes are detected at basically 20. Several methods to measure the location and amplitude of the peaks have been compared l producinal , g very consistent results particularn I . resulte th , f fitso s using empirical functione ar s consistent with the results of fits using a database of adiabatic inflationary spectra of the CMB [17].

Downloaded 02 Oct 2007 to 131.215.225.176. Redistribution subject to AIP license or copyright, see http://proceedings.aip.org/proceedings/cpcr.jsp 8000 a MAXIMA • BOOMERANG 6000 o DASI

4000 OJ_ o

2000

0 80 1000 0 60 1200 0 40 0 20 0 rnultipole

FIGURE 4, CMB anisotropy power spectrum detected by BOOMERanG, MAXIMA and DASI. Approximately uncorrelated bandpower plottee sar experiments e eacr th d fo f ho erroe .Th r bars represent statistical errors only.

COSMOLOGICAL SIGNIFICANCE AND PARAMETERS ESTIMATION

The presence of "acoustic" features in the power spectrum of the CMB has been forecast long time ago [37],[38]. bang bi gt resule modelho th e acoustif s i o tth t i ,n I c waves presen pre-recombinatioe th n i t n Universe theif o d r an , behaviour inside the acoustic horizon, in the presence of fluctuations in the density of the dominating form of matter. The same density fluctuations which are sources of the acoustic oscillations in the pre-recombination plasma are also responsibl gravitationae th r efo l collapse starting after recombination leadind formatioe ,an th large o gt th ef n o scal e nearbe th structuren i y e Universese e sw . Wiggles presenseee spectrub e mo th t larg e n ti th emf o scal e distribution of galaxies detected by the recent 2dF survey [39]; if this will be confirmed and if the wiggles will be found to be consistent with the modulation of the transfer function produced by "acoustic" features, it will be a wonderful success of this theory. e alternativTh e mode f formatioo l f galaxieo n s from topological defects shoul gaussian d no leaB o dt nCM anisotropies [40] faild reproduco ,an st observee eth d power spectrum onln [41] subdominane ca y b t :i t [42]. A large amount of work has been spent to accurately predict the power spectrum of the CMB in the adiabatic inflationary scenario. As of today, detailed fast codes are available [43], [44], and can be used to setup large databases of power spectra whico ,t measuree hth d spectru comparede b n mca . More wor done stils kb i properlo eo lt t y include in the analysis the possible existence of isocurvature modes [45]. thin I s framework locatioe th firse , th tpowe e f npeao th n ki r spectrum mainly depend curvature th e n so th f eo Universe. The first peak is due to those fluctuations that enter the horizon shortly before recombination, and have just enough time to fully compress before recombination happens. The size of these perturbations is thus very similar to the acoustie sizth f eo c horizo recombinationt na thue .sW hav e"standara d ruler" hundrew fe ,a d thousand light years long, placed at a distance of about 14 billion light years. If we take into account the fact that the Universe has expanded by a factor ~ 1000 since recombination conclude ,w e that these fluctuations should appea Thi. B ~s ra 1°CM spote th n si correcs i tgeometr e onlth Universf ye i th f yo Euclideans ei curvedt ,no average , i.eth f .i e mass-energy densite th f yo Univers 1)instead, = critica.If e O ( th mass-energ e e s ei , th lon y densit highes yi r than critica geometre 1)> ,th O l( y of space will have a positive curvature and the photons will travel along curved geodesies. The excess density will act a magnifyinsa gsame glassth ed wil fluctuationB an , l appeaCM e th spots ra n si s large opposite r Th tha . n1° e will happe densite th nf i loweys i r than critical, actin de-magnifyina s ga g glas producind san gtypicaa l angulare sizth f eo

Downloaded 02 Oct 2007 to 131.215.225.176. Redistribution subject to AIP license or copyright, see http://proceedings.aip.org/proceedings/cpcr.jsp a. B150A -42°

500 500

-202 -202 AT/ci AT/a . B400Bc 1 -42°

2000 [——'——'——'——'——•- 3000 8 = 118 D.O.F.=50 X =2055 ^ D.O.F.=50 2500 1500 2000

1000 1500

1000 500 500 0 0 -202 -2 AT/a

FIGURE 5. In the top row, we plot the 1-P distribution of the ratio A7}/*/of + 0^ for the 150 GHz map (dominated by CMB fluctuations) in a box at high galactic latitude (a) and in a box at intermediate galactic latitudes (b). In the lower row the same distributions are plotted for the map at 410 GHz, which is dominated by interstellar dust

fluctuations smaller tha cas y presencne an e1°.th n I typica a f eo fluctuatione l sizth f eo wils6 l produc e peaea th n ki power spectrum of the CMB at i\ = n/Q. By measuring the location of the peak it will thus be possible to measure quantitative Th . O e treatmen thif to s angular-siz distancs ev foune eb tesn [46]n di tca , [47] generaln .I , t\ decreases whe increasesnO locatioe firsth e t th t bu ,f npea o alss ki o controlle simple th OA0 y deb = relationshi- OnlA O f yi p ip ~ O~ 2 holds measuremene .Th t of t\ fro BOOMERane mth G power spectru mt\(213s = i 1 j^), whic consistenhs i t with a flat geometry of the Universe. Rigorous confidence intervals for the parameter O can be found with the Bayesian analysis of the full power spectrum as described below; frequentist methods are also being developed [48]. The ratio between the amplitude of the second peak and the amplitude of the first one depends mainly on the physical density of baryons Q&/? and on the tilt of the density fluctuations spectrum. A high density of baryons

favors compressions against rarefactions2 : the odd-order peaks (compression) are enhanced while the even-order peaks (rarefaction) are depleted. From the BOOMERanG power spectrum the ratio is (5450 ± 350) / (2220 ± 330) = (2.45 ± 0.52). Assuming a scale invariant power spectrum of the density fluctuations (n = 1), this corresponds to a physical density Q&/z2 ~ 0.02. Again, better constraint foune s ar mean Bayesiay e db th f so n analysi fule th l f poweso r spectrum as described below. In fact, a tilt of the density fluctuations spectrum (n < 1) has the same effect of a high baryons densit depletinn yi secone gth d peak with respec firse th t o onet thero degeneracs ,a s ei y betweeo tw e nth parametersquantitieo tw amplitud effecte e e th th th t n thirf e so so .th Bu df e o pea differente kar amplitude Th . e th f eo third pea increases ki higa y dhb baryon density primordia) 1 , < whil n decreases ( i d t ei l re densit a y db y fluctuation spectrum resule Th . thas ti t extendin observatione gth Io st ~ 1000 break degenerace sth y betwee Q&/zd an n2n , thus allowing a determination of both the parameters. It is important to stress the fact that our result for O^/z2 agrees with the constraint on Q&/i2 from the Big Bang Nucleosynthesis. In fact, the physical density of baryons affects the yield of the nuclear reactions happening in the first few minutes after the big bang. The resulting primordial abundances of light elements are measured by the optical absorption spectra of primordial clouds of matter [49]. It is evident that both the physics and the experimental methods involved in these two measurements of Q&/i are completely orthogonal to the CMB ones. The fact that the two

estimate Q&/?f so 2 agre welo es l shoul consideree db Bang dgreaa Bi gt tmodel succesHo e th 2 .f so The multiple peaks and dips are a strong prediction of the simplest adiabatic inflationary models, and more generally of models with passive, coherent perturbations. Although the main effect giving rise to them is regular sound compression and rarefaction of the photon-baryon plasma at photon decoupling, there are a number of influences that

Downloaded 02 Oct 2007 to 131.215.225.176. Redistribution subject to AIP license or copyright, see http://proceedings.aip.org/proceedings/cpcr.jsp make the regularity only roughly true. The best way to extract all the information encoded in the data is by comparison to a large database of Q spectra. In order to limit the size of the database, we considered for the first approach the class of adiabatic inflationary models. We have explored a parameter space with 6 discrete parameters and a continuous one. The parameters ranged as follows: Ow = 0.11,..., 1.085, in steps of 0.025; Qb = 0.015,...,0.20, in steps of 0.015; OA = 0.0,...,0.975, in steps of 0.025; h = 0.25,...,0.95, in steps of 0.05; spectral index of the primordial density perturbations ns = 0.50,..., 1.50, in steps of 0.02, ic = 0., ..,0.5, in steps of 0.1. The overall amplitude CIQ, expressed in units of C^QBE, is allowed to vary continuously. We used the BOOMERANG power spectrum expressed

as 18 bandpowers C [15] and we computed the likelihood for the cosmological model C as exp(—%/2), where

b b 2 2 —b C(C b2C )M~^y = —y Cy(C ). Her covariancee Mth s bi y e matri measuree th f xo d bandpowers appropriatn ;a Cs i b e band average of Q. A 10% Gaussian-distributed calibration error in the gain and a 1.4' (13%) beam uncertainty were included in the analysis as additional parameters with gaussian priors. The COBE-DMR bandpowers used were those of [50], obtained fro RADPACe mth K distributio confidenc% n 95 [51] e Th . e interval parametere th r sfo fine sn w di this way depend to some extent on the priors assumed. Using COBE and BOOMERanG data only, with a weak prior 2 0.90< 0.4 h ,5 < significantl y constrains three parameters 1.15,0.< 0.01 1.d Q < 1 an < n Q.5 < 8 9 < b 0.029h:0. < . Using more restrictive priors, deriving fro propertiee mth large th ef s o scal e distributio Galaxief no s F)d (ar o ,gan the data of high-redshift supernovae, or the measurement of h by the HST, produces narrower, consistent intervals for these parameters [15], [17]. This fact suggests a good overall consistency of the present cosmological paradigm. Including these priors alss i t o,i possibl constraio e t additiona o tw e nth l form mass-energf so y contributin totae th lgo t mass-energy density in the Universe, i.e. dark matter and dark energy. We find that the 95% confidence intervals for

Q0.3 Oe d b Ahar O6 < an 0.70.0 A< d 2Q9an < b h0.1< 8 (LSS prior); 0.5 O2< 0.80.0A< d 81Qan < b h0.1< 7 2 2 2 2 (SNla prior); 0.40 < OA < 0.84 and 0.06 < Qbh < 0.26 (HST h prior). The detection of a non-zero OA comes thus from independent path setd formidablsa an e challeng understandinr ou o et fundamentaf go l physics [52].

CONCLUSIONS

BOOMERane Th G experimen produces tha d multi-frequency microwave mapth f so e sky, wher structure eth e th f eo CMB has been resolved with high signal to noise ratio. The structures in the CMB are gaussian, and their power spectrum features three peaks. Thi consistens si t wit presence hth acoustif eo c oscillation primevae th n si l plasmat .I also predictionfite sth adiabatie th f so c inflationary scenario value e cosmologicae .th Th f so l parameters inferre thin di s scenario poin flaa to t t universe with nearly scale-invariant initial adiabatic perturbation significana d san t contribution of dark energy to the total density of the Universe. Significant work remains to be done with the BOOMERanG data. We are working to analyze all the remaining channel mora r efo accuratB s sensitivCM e eth determinatioo et powee th f no r spectrum paralleln .I currentl e ar e ,w y assessin gaussianite gth mape th f syo with different methods usin.e Also observationar e ge th ,w Galactif so c sourcen si orde improvo rt gai e bead eth nan m calibration accuracy searc.A Sunyaev-Zeldovicr hfo h directio effece th e n i tth f no rich clusters of Galaxies present in the observed region is also being carried out. Methods for components separation highee andate th df th a o r frequency channe beine lar g use investigatdo t propertiee eth interstellaf so r cirrus clouds.

ACKNOWLEDGMENTS

This activity has been supported by the University of Rome La Sapienza, Programma Nazionale di Ricerche in Antartid Agenzid ean a Spaziale Univy Italianb f USAd n o i . an Italyn PPAR F ay i b ,K NAS y NS b U , d Cn i A an Toronto in Canada.

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