R. A. Watson

Detection of Anomalous Microwave Emission in the Perseus Molecular Cloud with the COSMOSOMAS Experiment

We present direct evidence for anomalous microwave emission in the Perseus molecular cloud, which shows a clear rising spectrum from 11 to 17 GHz in the data from the COSMOSOMAS experiment. By extending the frequency coverage using W ilkinson Microwave Anisotropy Probe maps convolved with the COSMOSOMAS scanning pattern, we reveal a peak flux density of 42 ± 4 Jy at 22 GHz integrated over an extended area of 165 × 10 centered on R.A. = 554 ± 01 and decl. = +318 ± 01 (J2000). The flux density that we measure at this frequency is nearly an order of magnitude higher than can be explained in terms of normal Galactic emission processes (synchrotron, free-free, and thermal dust). An extended IRAS dust feature, G159.6-18.5, is found near this position, and no bright unresolved source that could be an ultracompact H II region or gigahertz-peaked source could be found. An adequate fit for the spectral density distribution can be achieved from 10 to 50 GHz by including a very significant contribution from electric dipole emission from small spinning dust grains.

The Tenerife Cosmic Microwave Background Maps: Observations and First Analysis

The results of the Tenerife cosmic microwave background (CMB) experiments are presented. These observations cover 5000 and 6500 deg2 on the sky at 10 and 15 GHz, respectively, centered on decl. ~ +35°. The experiments are sensitive to multipoles l = 10-30 that correspond to the Sachs-Wolfe plateau of the CMB power spectra. The sensitivity values of the data are ~31 and ~12 μK at 10 and 15 GHz, respectively, in a beam-size region (5° × 5°). The data at 15 GHz show clear detection of structure at high Galactic latitude; the results at 10 GHz are compatible with these, but at lower significance. A likelihood analysis of the 10 and 15 GHz data at high Galactic latitude, assuming a flat CMB band power spectrum, gives a signal ΔTl = 30 μK (68% C.L.). Including the possible contaminating effect due to the diffuse Galactic component, the CMB signal is ΔTl = 30 μK. These values are stable against the Galactic cut chosen. Assuming a Harrison-Zeldovich spectrum for the primordial fluctuations, the above values imply an expected quadrupole Qrms-ps = 20 μK, which agrees with previous results from these experiments, and which are compatible with the COBE DMR data in the case of the standard inflationary cold dark matter models.

COSMOSOMAS: a circular scanning instrument to map the sky at centimetric wavelengths

We describe the first instrument of a cosmic microwave background experiment for mapping cosmological structures on medium angular scales (the COSMOSOMAS experiment) and diffuse Galactic emission. The instrument is located at Teide Observatory (Tenerife) and is based on a circular scanning sky strategy. It consists of a 1-Hz spinning flat mirror directing the sky radiation into a 1.8-m off-axis paraboloidal antenna, which focuses it on to a cryogenically cooled HEMT-based receiver operating in the frequency range 12–18xa0GHz. n n n nThe signal is split by a set of three filters, allowing simultaneous observations at 13, 15 and 17xa0GHz, each with a 1-GHz bandpass. A 1°–5° resolution sky map complete in right ascension and covering 20° in declination is obtained each day at these frequencies. The observations presented here correspond to the first months of operation, which have provided a map of 9000xa0deg2 on the sky centred at Dec.=+31° with sensitivities of 140, 150 and 250xa0μK per beam area in the channels at 13, 15 and 17xa0GHz, respectively. We discuss the design and performance of the instrument, the atmospheric effects, the reliability of the data obtained and prospects of achieving a sensitivity of 30xa0μK per beam in 2 years of operation.

A 33-GHz Very Small Array survey of the Galactic plane from l = 27{\deg} to 46{\deg}

The Very Small Array (VSA) has been used to survey the l = 27 to 46 deg, |b|<4 deg region of the Galactic plane at a resolution of 13 arcmin. The survey consists of 44 pointings of the VSA, each with a r.m.s. sensitivity of ~90 mJy/beam. These data are combined in a mosaic to produce a map of the area. The majority of the sources within the map are HII regions. We investigated anomalous radio emission from the warm dust in 9 HII regions of the survey by making spectra extending from GHz frequencies to the FIR IRAS frequencies. Acillary radio data at 1.4, 2.7, 4.85, 8.35, 10.55, 14.35 and 94 GHz in addition to the 100, 60, 25 and 12 micron IRAS bands were used to construct the spectra. From each spectrum the free-free, thermal dust and anomalous dust emission were determined for each HII region. The mean ratio of 33 GHz anomalous flux density to FIR 100 micron flux density for the 9 selected HII regions was 1.10 +/-0.21x10^(-4). When combined with 6 HII regions previously observed with the VSA and the CBI, the anomalous emission from warm dust in HII regions is detected with a 33 GHz emissivity of 4.65 +/- 0.4 micro K/ (MJy/sr) at 11.5{sigma}. The anomalous radio emission in HII regions is on average 41+/-10 per cent of the radio continuum at 33 GHz.

The QUIJOTE-CMB Experiment: Progress Report

RICARDO GENOVA-SANTOS1∗, R. REBOLO1, J.A. RUBINO-MARTIN1, M. AGUIAR1, F. GOMEZ-RENASCO1, J.M. HERREROS1, S. HILDEBRANDT1, R. HOYLAND1, C. LOPEZ-CARABALLO1, R. RODRIGUEZ1, M. TUCCI1, E. MARTINEZ-GONZALEZ2, R.B. BARREIRO2, F.J. CASAS2, R. FERNANDEZ-COBOS2, D. HERRANZ2, M. LOPEZ-CANIEGO2, P. VIELVA2, E. ARTAL3, B. AJA3, J.L. CANO3, L. DE LA FUENTE3, A. MEDIAVILLA3, J.P. PASCUAL3, E. VILLA3, L. PICCIRILLO4, R. BATTYE4, R. DAVIES4, R. DAVIS4, C. DICKINSON4, B. MAFFEI4, G. PISANO4, R.A. WATSON4, M. BROWN5, A. CHALLINOR5, K. GRAINGE5, M. HOBSON5, A. LASENBY5, R. SAUNDERS5, P. SCOTT5, J. ARINO6, B. ETXEITA6, A. GOMEZ6, C. GOMEZ6, G. MURGA6, J. PAN6, R. SANQUIRCE6 and A. VIZCARGUENAGA6 1 Instituto de Astrofisica de Canarias, C/Via Lactea, s/n, 38200 La Laguna, Tenerife, Spain

New Results on CMB Structure From the Tenerife Experiments

Temperature fluctuations in the CMB (Cosmic Microwave Background) are a key prediction of cosmological models of structure formation in the early Universe. Observations at the Teide Observatory, Tenerife using radiometers operating at 10, 15 and 33 GHz have revealed individual hot and cold features in the microwave sky at high Galactic latitudes. These well-defined features are not atmospheric or Galactic in origin; they represent the first detection of individual primordial fluctuations in the CMB. Their intensity is defined by an intrinsic rms amplitude of 54-10 +14 µK for a model with a coherence angle of 4°. The expected quadrupole term for a Harrison-Zel’dovich spectrum is Q RMS—PS = 26 ± 6 µK. When our data at Dec=+40° are compared with the COBE DMR two-year data, the presence of individual features is confirmed. New experiments to detect structure on smaller scales are described.

MAPPING WITH THE JODRELL BANK-TENERIFE RADIOMETERS

Following the first identification in 1967 of the cosmic microwave background) (CMB) and the detection of the dipole component2j3) due to the Local Group motion, there has been a N 25 year search for intrinsic structure in the CMB. The earliest predictions4) suggested that rms values of ATIT for this structure might be of order (where T is the mean temperature of 2.7 K). As experimental limits on ATIT were pushed successively lower, theoretical models for CMB structure were refined to match the observations. The recent unambiguous detection of CMB s t r ~ c t u r e ~ ~ ) confirmed by independent experiments has established the fluctuation amplitude to be ATIT N on scales of several degrees and larger. The subject is now ready to move on to the mapping of individual structures in the CMB to provide the basic observational input to cosmogony. On the angular scales investigated in the Tenerife experiments, the main contribution to the CMB structure is the Sachs-Wolfe effectg) in which the CMB intensity is affected by the gravitational potential of large-scale mass concentrations in front of the last-scattering surface. In contrast to this scalar contribution, there is a possible tensor contribution) t o the CMB structure arising from gravitational radiation originating in the inflationary era. The weakness of the intrinsic signals (rms N 30 50 ILK) requires a careful assessment of the systematic effects. These can arise from the environment of the experiment, the atmosphere, solar system objects (Earth, Moon and Sun), the Galaxy and celestial point sources. The contribution of the effects related to the environment and the solar system objects can be established over long observing periods (ideally years) while the extra-solar system contribution is determined from observations covering a sufficiently wide range of frequencies. The ultimate confirmation conies from a comparison of independent experiments over a wide frequency range.