Dust emission in massive star-forming regions with PRONAOS: the Orion and M17 molecular clouds

The balloon-borne submillimeter instrument PRONAOS has observed one square degree areas towards the Orion and M17 molecular clouds. The 2' - 3.5' resolution maps obtained in four wide wavelength bands between 200 microns and 600 microns, exhibit the dust distribution in these regions. We analyze the temperature and spectral index of the dust, and we show the anticorrelation between these two parameters. We derive estimations of the ISM column densities and masses in these regions.Comment: 1 fig. JPEG, to appear in the proc. of the Infrared and Submm Space Astronomy coll., held in memory of Guy Serra, Toulouse, June 11-13, 200

How to make CMB maps from huge timelines with small computers

We present in this article two different ways to make CMB maps in practice, from large timelines. One is to make a simple destriping, fitting the data and using the scan intercepts to remove the low frequency noise (stripes). The second, optimal, is to resolve linearly the map-making problem, which in case of big timelines must be simplified and changed from matrices to vectors for the calculations. Assuming few conditions on the noise, it is possible to make fast map-making tools.Comment: 1 fig., proceeding of the "Mining the Sky" conference in Garching, Germany, 200

Map-making methods for Cosmic Microwave Background experiments

The map-making step of Cosmic Microwave Background data analysis involves linear inversion problems which cannot be performed by a brute force approach for the large timelines of today. We present in this article optimal vector-only map-making methods, which are an iterative COBE method, a Wiener direct filter and a Wiener iterative method. We apply these methods on diverse simulated data, and we show that they produce very well restored maps, by removing nearly completely the correlated noise which appears as intense stripes on the simply pixel-averaged maps. The COBE iterative method can be applied to any signals, assuming the stationarity of the noise in the timeline. The Wiener methods assume both the stationarity of the noise and the sky, which is the case for CMB-only data. We apply the methods to Galactic signals too, and test them on balloon-borne experiment strategies and on a satellite whole sky survey.Comment: 8 pages without the figures, 11 JPEG figures out of the text, MNRAS, in pres

Submillimeter dust emission of the M17 complex measured with PRONAOS

We map a 50' x 30' area in and around the M17 molecular complex with the French submillimeter balloon-borne telescope PRONAOS, in order to better understand the thermal emission of cosmic dust and the structure of the interstellar medium. The PRONAOS-SPM instrument has an angular resolution of about 3', corresponding to a size of 2 pc at the distance of this complex, and a high sensitivity up to 0.8 MJy/sr. The observations are made in four wide submillimeter bands corresponding to effective wavelengths of 200, 260, 360 and 580 um. Using an improved map-making method for PRONAOS data, we map the M17 complex and faint condensations near the dense warm core. We derive maps of both the dust temperature and the spectral index, which vary over a wide range, from about 10 K to 100 K for the temperature and from about 1 to 2.5 for the spectral index. We show that these parameters are anticorrelated, the cold areas (10-20 K) having a spectral index around 2, whereas the warm areas have a spectral index between 1 and 1.5. We discuss possible causes of this effect, and we propose an explanation involving intrinsic variations of the grain properties. Indeed, to match the observed spectra with two dust components having a spectral index equal to 2 leads to very large and unlikely amounts of cold dust. We also give estimates of the column densities and masses of the studied clumps. Three cold clumps (14-17 K) could be gravitationally unstable.Comment: 16 pages, 4 figures, accepted June 2002 in Astronomy & Astrophysic

Planck LFI-only mission extension

The main reason for the extension of the Planck mission beyond the lifetime of the 0.1-K dilution cooler is to obtain further data which will improve our understanding of systematic effects. In the present report, we justify the continuation of the current scanning strategy in order to obtain a sixth survey, allowing for better sensitivity and further “jackknife” (survey difference) tests. The fifth survey is already improving the estimates of the polarisation leakage for two of the LFI horns, and this improvement will continue with the sixth survey during the extension. In addition, we confirm the “deep rings” scanning strategy to improve mapping of the beams using radio sources, specifically Jupiter and the Crab Nebula. We propose to maintain the current spin rate: no other changes are foreseen, except the possibility to increase the sampling of some house-keeping data

Construction optimale d'images bolométriques (contribution à l'étude du milieu interstellaire et du rayonnement fossile)

TOULOUSE3-BU Sciences (315552104) / SudocMEUDON-Observatoire (920482302) / SudocSudocFranceF