Detection of Anomalous Microwave Emission in the Pleiades Reflection Nebula with WMAP and the COSMOSOMAS Experiment

We present evidence for anomalous microwave emission (AME) in the Pleiades reflection nebula, using data from the seven-year release of the Wilkinson Microwave Anisotropy Probe (WMAP) and from the COSMOSOMAS experiment. The flux integrated in a 1-degree radius around R.A.=56.24^{\circ}, Dec.=23.78^{\circ} (J2000) is 2.15 +/- 0.12 Jy at 22.8 GHz, where AME is dominant. COSMOSOMAS data show no significant emission, but allow to set upper limits of 0.94 and 1.58 Jy (99.7% C.L.) respectively at 10.9 and 14.7 GHz, which are crucial to pin down the AME spectrum at these frequencies, and to discard any other emission mechanisms which could have an important contribution to the signal detected at 22.8 GHz. We estimate the expected level of free-free emission from an extinction-corrected H-alpha template, while the thermal dust emission is characterized from infrared DIRBE data and extrapolated to microwave frequencies. When we deduct the contribution from these two components at 22.8 GHz the residual flux, associated with AME, is 2.12 +/- 0.12 Jy (17.7-sigma). The spectral energy distribution from 10 to 60 GHz can be accurately fitted with a model of electric dipole emission from small spinning dust grains distributed in two separated phases of molecular and atomic gas, respectively. The dust emissivity, calculated by correlating the 22.8 GHz data with 100-micron data, is found to be 4.36+/-0.17 muK/MJy/sr, a value that is rather low compared with typical values in dust clouds. The physical properties of the Pleiades nebula indicate that this is indeed a much less opaque object than others were AME has usually been detected. This fact, together with the broad knowledge of the stellar content of this region, provides an excellent testbed for AME characterization in physical conditions different from those generally explored up to now.Comment: Accepted for publication in ApJ. 12 pages, 8 figure

interface trap state characterization of metal insulator semiconductor structures based on photosensitive organic materials

Abstract Flexible organic and printed electronics has led in the last years to exciting applications, especially for what concerns devices incorporating photosensitive materials. Among the latter, organic field-effect phototransistors are a promising technology because of the high light-sensitivity and the possibility of being integrated within more complex systems. Nevertheless, their optimization has not been thoroughly investigated and considerable variations are often observed in their behavior. In this framework, the most critical aspect is represented by the interface formed between the organic semiconductor and the employed dielectric layer. In our contribution, we have fabricated metal-insulator-semiconductor (MIS) structures based on the archetypal photosensitive organic materials poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PC 61 BM) on Silicon/SiO 2 substrates, exploiting their blend in a bulk heterojunction configuration. The MIS structures have been characterized by means of admittance spectroscopy to study the properties of the trap distribution at the interface between the organic semiconductors and the silicon oxide insulating layer. The complex behavior of the capacitance and loss diagrams has been interpreted with a simple electrical model to extract the density of the traps at the interface between the insulator and the semiconductor. It is shown that in the blend-based MIS device several peaks arise in the loss diagram with respect to the only P3HT MIS device. This could be attributed to a different interaction between the single species in the bulk heterojunction and the silicon oxide layer. Furthermore, the reported values of trap densities result in the range of those determined for analogous structures and materials

Enhanced Inflation in the Dirac-Born-Infeld framework

We consider the Einstein equations within the DBI scenario for a spatially flat Friedmann-Robertson-Walker (FRW) spacetime without a cosmological constant. We derive the inflationary scenario by applying the symmetry transformations which preserve the form of the Friedmann and conservation equations. These form invariance transformations generate a symmetry group parametrized by the Lorentz factor \ga. We explicitly obtain an inflationary scenario by the cooperative effect of adding energy density into the Friedmann equation. For the case of a constant Lorentz factor, and under the slow roll assumption, we find the transformation rules for the scalar and tensor power spectra of perturbations as well as their ratio under the action of the form invariance symmetry group. Within this case and due to its relevance for the inflationary paradigm, we find the general solution of the dynamical equations for a DBI field driven by an exponential potential and show a broad set of inflationary solutions. The general solution can be split into three subsets and all these behave asymptotically as a power law solution at early and at late times.Comment: 9 pages, revtex 4.

Cosmological hydrogen recombination: populations of the high level sub-states

We present results for the spectral distortions of the Cosmic Microwave Background (CMB) arising due to bound-bound transitions during the epoch of cosmological hydrogen recombination at frequencies down to nu~100MHz. We extend our previous treatment of the recombination problem now including the main collisional processes and following the evolution of all the hydrogen angular momentum sub-states for up to 100 shells. We show that, due to the low baryon density of the Universe, even within the highest considered shell full statistical equilibrium (SE) is not reached and that at low frequencies the recombination spectrum is significantly different when assuming full SE for n>2. We also directly compare our results for the ionization history to the output of the Recfast code, showing that especially at low redshifts rather big differences arise. In the vicinity of the Thomson visibility function the electron fraction differs by roughly -0.6% which affects the temperature and polarization power spectra by <~1%. Furthermore we shortly discuss the influence of free-free absorption and line broadening due to electron scattering on the bound-bound recombination spectrum and the generation of CMB angular fluctuations due to scattering of photons within the high shells.Comment: 12 pages, 11 figures, submitted to MNRAS, revised version, included two new figures, Sect. 3.4 adde