Model of the polarized foreground diffuse Galactic emissions from 33 to 353 GHz

We present 3D models of the Galactic magnetic field including regular and turbulent components, and of the distribution of matter in the Galaxy including relativistic electrons and dust grains. By integrating along the line of sight, we construct maps of the polarized Galactic synchrotron and thermal dust emissions for each of these models. We perform a likelihood analysis to compare the maps of the Ka, Q, V and W bands of the Wilkinson Microwave Anisotropy Probe (Wmap) and the 353 GHz Archeops data to the models obtained by varying the pitch angle of the regular magnetic field, the relative amplitude of the turbulent magnetic field and the extrapolation spectral indices of the synchrotron and thermal dust emissions. The best-fit parameters obtained for the different frequency bands are very similar and globally the data seem to favor a negligible isotropic turbulent magnetic field component at large angular scales (an anisotropic line-of-sight ordered component can not be studied using these data). From this study, we conclude that we are able to propose a consistent model of the polarized diffuse Galac- tic synchrotron and thermal dust emissions in the frequency range from 33 to 353 GHz, where most of the CMB studies are performed and where we expect a mixture of these two main foreground emissions. This model can be very helpful to estimate the contamination by foregrounds of the polarized CMB anisotropies, for experiments like the Planck satellite.Comment: 22 pages, 4 figure

A Sunyaev-Zel'dovich map of the massive core in the luminous X-ray cluster RXJ1347-1145

We have mapped the Sunyaev-Zel'dovich decrement (hereafter SZ) in the direction of the most luminous X-ray cluster known to date, RXJ1347-1145, at z=0.451. This has been achieved with an angular resolution of about 23'' using the Diabolo photometer running on the IRAM 30 meter radio telescope. We present here a map of the cluster central region at 2.1mm. The Comptonization parameter towards the cluster center, \yc=(12.7^{+2.9}_{-3.1})\times 10^{-4}, corresponds to the deepest SZ decrement ever observed. Using the gas density distribution derived from X-ray data, this measurement implies a gas temperature \te=16.2 \pm 3.8 keV. The resulting total mass of the cluster is, under hydrostatic equilibrium, $M(r<1 Mpc)=(1.0 \pm 0.3) \times 10^{15} M_\odot$ for a corresponding gas fraction $f_{gas}(r<1 Mpc)=(19.5 \pm 5.8)$.Comment: 16 pages, 2 figures, accepted for publication in ApJ Letter

Search for grain growth towards the center of L1544

In dense and cold molecular clouds dust grains are surrounded by thick icy mantles. It is however not clear if dust growth and coagulation take place before the switch-on of a protostar. This is an important issue, as the presence of large grains may affect the chemical structure of dense cloud cores, including the dynamically important ionization fraction, and the future evolution of solids in protoplanetary disks. To study this further, we focus on L1544, one of the most centrally concentrated pre-stellar cores on the verge of star formation, and with a well-known physical structure. We observed L1544 at 1.2 and 2 mm using NIKA, a new receiver at the IRAM 30 m telescope, and we used data from the Herschel Space Observatory archive. We find no evidence of grain growth towards the center of L1544 at the available angular resolution. Therefore, we conclude that single dish observations do not allow us to investigate grain growth toward the pre-stellar core L1544 and high sensitivity interferometer observations are needed. We predict that dust grains can grow to 200 $\mu$m in size toward the central ~300 au of L1544. This will imply a dust opacity change by a factor of ~2.5 at 1.2 mm, which can be detected using the Atacama Large Millimeter and submillimeter Array (ALMA) at different wavelengths and with an angular resolution of 2".Comment: 12 pages, 14 figures. Accepted for publication in A&

A Characterization of the Diffuse Galactic Emissions in the Anticenter of the Galaxy

Using the Archeops and WMAP data, we perform a study of the anticenter Galactic diffuse emissions—thermal dust, synchrotron, free-free, and anomalous emissions—at degree scales. The high-frequency data are used to infer the thermal dust electromagnetic spectrum and spatial distribution allowing us to precisely subtract this component at lower frequencies. After subtraction of the thermal dust component, a mixture of standard synchrotron and free-free emissions does not account for the residuals at these low frequencies. Including the all-sky 408 MHz Haslam data we find evidence for anomalous emission with a spectral index of −2.5 in units. However, we are not able to provide coclusion regarding the nature of this anomalous emission in this region. For this purpose, data between 408 MHz and 20 GHz covering the same sky region are needed

Dust in the diffuse ISM as revealed by DIRBE observations

The weekly averaged DIRBE full sky images have been processed to separate the various components contributing to the total brightness in the various bands. The zodiacal emission, which dominates at 12 and 25 μm and the zodiacal dust scattering at λ<5 μm are both accounted for using an empirical fit to the data. The diffuse stellar emission which dominates at λ<5 μm is determined using the shortest DIRBE photometric bands at 1.25 and 2.2 μm and a standard NIR extinction law. Preliminary results based on the first release of the DIRBE data have been presented in Bernard et al. 1994. When the zodiacal light and stellar emission are subtracted, significant emission remains above 2.2 μm, which follows the general distribution of the dust emission as seen in the IRAS bands. The DIRBE images therefore allow to extend our knowledge of the dust emission spectrum below 12 μm and above 100 μm. In the L(3.5 μm) and M(4.9 μm) bands, the dust emission can be seen not only toward the galactic plane but also in diffuse regions above the plane as well as toward closeby molecular complexes (ρ‐Ophiuchi, Orion, Taurus,...). The existence of NIR dust emission in cold and diffuse regions strongly suggests transiently heated small dust particles as the carrier. The dust NIR spectrum is generally consistent with the dust model of Désert et al. 1990. In particular, the dust emission increases from 4.9 to 3.5 μm, which can be attributed to the contribution of the 3.3 μm emission feature of Polycyclic Aromatic Hydrocarbons (PAH). Significant continuum emission, or other feature emission, is also required to explain the observed brightness in the L band and the AROME ballon experiment results at low galactic latitude

Simulations of the Microwave Sky and of its ``Observations''

Here follows a preliminary report on the construction of fake millimeter and sub-millimeter skies, as observed by virtual instruments, e.g. the COBRA/SAMBA mission, using theoretical modeling and data extrapolations. Our goal is to create maps as realistic as possible of the relevant physical contributions which may contribute to the detected signals. This astrophysical modeling is followed by simulations of the measurement process itself by a given instrumental configuration. This will enable a precise determination of what can and cannot be achieved with a particular experimental configuration, and provide a feedback on how to improve the overall design. It is a key step on the way to define procedures for the separation of the different physical processes in the future observed maps. Note that this tool will also prove useful in preparing and analyzing current (\eg\ balloon borne) Microwave Background experiments. Keywords: Cosmology -- Microwave Background Anisotropies.Comment: 6 pages of uuencoded compressed postscript (1.2 Mb uncompressed), to appear in the proceedings of the meeting "Far Infrared and Sub-millimeter Space Missions in the Next Decade'', Paris, France, Eds. M. Sauvage, Space Science Revie

Deep Galaxy survey at 6.75 micron with the ISO satellite

Deep 6.75um mid-IR ISOCAM observations were obtained of the Canada-France Redshift Survey (CFRS) 1415+52 field with the Infrared Space Observatory. The identification of the sources with optical counterparts is described in detail, and a classification scheme is devised which depends on the S/N of the detection and the inverse probability of chance coincidence. 83% of the 54 ISOCAM sources are identified with Iab<23.5 counterparts. The (I-K)ab colors, radio properties, spectrophotometric properties and frequency of nuclear activity of these counterparts differ on average from those of typical CFRS galaxies. CFRS spectra are available for 21 of the sources which have Iab <= 22.5 (including 7 stars). Most of the strongest sources are stars or AGN. Among the non--stellar counterparts with spectra, 40% are AGNs, and 53% are galaxies that display star formation activity and/or significant contributions of A stars. The ISOCAM sources also display an IR excess, even when compared with heavily-reddened local starburst galaxies. An upper limit of 30% of extragalactic ISO sources could be at z>1 of the 44 S6.75um > 150uJy sources which are non-stellar (7 "spectroscopic" and 3 "photometric" stars excluded)Comment: 13 pages, 12 figures. Accepted for publication in A

Gran Telescopio Canarias OSIRIS Transiting Exoplanet Atmospheric Survey: Detection of potassium in XO-2b from narrowband spectrophotometry

We present Gran Telescopio Canarias (GTC) optical transit narrow-band photometry of the hot-Jupiter exoplanet XO-2b using the OSIRIS instrument. This unique instrument has the capabilities to deliver high cadence narrow-band photometric lightcurves, allowing us to probe the atmospheric composition of hot Jupiters from the ground. The observations were taken during three transit events which cover four wavelengths at spectral resolutions near 500, necessary for observing atmospheric features, and have near-photon limited sub-mmag precisions. Precision narrow-band photometry on a large aperture telescope allows for atmospheric transmission spectral features to be observed for exoplanets around much fainter stars than those of the well studied targets HD209458b and HD189733b, providing access to the majority of known transiting planets. For XO-2b, we measure planet-to-star radius contrasts of R_pl/R_star=0.10508+/-0.00052 at 6792 Ang, 0.10640+/-0.00058 at 7582 Ang, and 0.10686+/-0.00060 at 7664.9 Ang, and 0.10362+/-0.00051 at 8839 Ang. These measurements reveal significant spectral features at two wavelengths, with an absorption level of 0.067+/-0.016% at 7664.9 Ang due to atmospheric potassium in the line core (a 4.1-sigma significance level), and an absorption level of 0.058+/-0.016% at 7582 Ang, (a 3.6-sigma significance level). When comparing our measurements to hot-Jupiter atmospheric models, we find good agreement with models which are dominated in the optical by alkali metals. This is the first evidence for potassium in an extrasolar planet, an element that has long been theorized along with sodium to be a dominant source of opacity at optical wavelengths for hot Jupiters.Comment: 11 pages, 6 figures, accepted in A&A, minor changes to wording, primarily section 4.2, and the title has also been slightly modifie