CARA Science: CMBR Figures


Figure 1


Click to retrieve larger image.

Image of anisotropy in the Cosmic Microwave Background (CMB) measured by the CARA's Python telescope at the South Pole. The top image shows structure in the CMB coded with red for hot spots and blue for cold spots. The lower panel shows the signal to noise ratio for the features in the top plot indicating that the structure is indeed real and not an artifact of noise. The CMB provides a snapshot of the universe when it was only 300,000 years old, revealing the structure which eventually evolves into the rich structure seen in the present universe which is roughly 50,000 times older (Coble et al. 1999, Coble 1999).

Figure 2

Measurements of the CMB power spectrum made using Python and Viper. The Python flat band power points (* symbols) are simultaneously estimated in 7 l bands including the cross-modulation theory and noise covariances (Coble et al. 1999, Coble 1999). The Python data provide an important link between the COBE data at large angular scales and data from instruments at intermediate scales such as CARA instruments Viper and DASI. The five Viper data points (open square symbols) represent the first results from Viper. The Viper data continue to accumulate. Taken together, the Python and Viper data show that the power spectrum has a peak near l = 200, the location expected for a geometrically flat universe. Einstein showed that for a critical matter density of the universe, the geometry of the universe would be flat. Direct measurements of the matter density, however, indicate that it is only equal to one third of the critical value. The Python and Viper data thus strongly indicate that another form of energy must exist and dominates the present energy density of the universe.

Figure 3

Viper Sunyaev-Zeldovic effect image of A3667. The gravitational pull of dark matter within a cluster of galaxies traps a hot gas of electrons. These electrons scatter off protons creating x-ray emission, shown here as contours. The x-ray emission is brightest at the center. The electrons also scatter cosmic microwave background (CMB) photons, producing a dimming shown here as a blue color. This CMB dimming is known as the Sunyaev-Zel'dovich effect (SZE). By carefully mapping both the x-ray emission and the SZE we can determine the distance to the cluster which allows us to determine the expansion speed of the universe. The cluster, known as A3667, is the first to be mapped in SZE using the Viper telescope. Hundreds of galaxies are also trapped in the cluster gravitational potential, but they are not visible at these wavelengths.

Figure 4


Click to retrieve larger image.

Undergraduate REU student Jon Mitchell (UCSB) uses the numerical mill as a coordinate measuring machine to test the shape of the ACBAR tertiary mirror, which was made in the UCSB shop and polished by Jon. After taking several hundred points, Jon solves for the best fit parameters for the mirror to quantify the rms surface accuracy.

Figure 5

A photograph of a complete set of feed horns for the 16 element ACBAR bolometer array. The feed horns cover four separate mm & submm bands to provide excellent sensitivity to the Cosmic Microwave Background (CMB) radiation and the abililty to differentiate the weak CMB signals from emission from Earth's atmosphere and interstellar dust. ACBAR will be used on the South Pole 2.1 m Viper telescope.

Figure 6

figure

The Degree Angular Scale Interferometer (DASI) assembled at the University of Chicago for testing. DASI is a 13-element interferometric array designed to obtain highly sensitive and detailed images of anisotropy in the cosmic microwave background (CMB) and to determine its angular power spectrum. The data will allow a direct view of the universe when only 300,000 years old, roughly one part in 50,000 of its present age. The structures imaged by DASI will be representative of the seeds of all the structure found in the universe today. DASI will be deployed to the NSF Amundsen-Scott research station at the South Pole in December 1999.