First detection of the Sunyaev Zel'dovich effect increment at λ < 650 μm

The Sunyaev-Zel'dovich (SZ) effect is a spectral distortion of the cosmic microwave background as observed through the hot plasma in galaxy clusters. This distortion is a decrement in the CMB intensity for λ > 1.3 mm, an increment at shorter wavelengths, and small again by λ ~ 250 μm. As part of the Herschel Lensing Survey (HLS) we have mapped 1E0657–56 (the Bullet cluster) with SPIRE with bands centered at 250, 350 and 500 μm and have detected the SZ effect at the two longest wavelengths. The measured SZ effect increment central intensities are ΔI_0 = 0.097 ± 0.019 MJy sr^-1 at 350 μm and ΔI_0 = 0.268 ± 0.031 MJy sr^-1 at 500 μm, consistent with the SZ effect spectrum derived from previous measurements at 2 mm. No other diffuse emission is detected. The presence of the finite temperature SZ effect correction is preferred by the SPIRE data at a significance of 2.1σ, opening the possibility that the relativistic SZ effect correction can be constrained by SPIRE in a sample of clusters. The results presented here have important ramifications for both sub-mm measurements of galaxy clusters and blank field surveys with SPIRE.

Analysis of the spectral response of fractal antennas related with its geometry and current paths

Fractal antennas have been proposed to improve the bandwidth of resonant structures and optical antennas. Their multiband characteristics are of interest in radiofrequency and microwave technologies. In this contribution we link the geometry of the current paths built-in the fractal antenna with the spectral response. We have seen that the actual currents owing through the structure are not limited to the portion of the fractal that should be geometrically linked with the signal. This fact strongly depends on the design of the fractal and how the different scales are arranged within the antenna. Some ideas involving materials that could actively respond to the incoming radiation could be of help to spectrally select the response of the multiband design.