arXiv subjects

R. Caldwell

Publications and source records attributed to R. Caldwell.

4 recordsLinked to original sources

arXiv2002

Cosmological Parameters, Dark Energy and Large Scale Structure

We review the current status of cosmological parameters, dark energy and large-scale structure, from a theoretical and observational perspective. We first present the basic cosmological parameters and discuss how they are measured with different observational techniques. We then describe the recent evidence for dark energy from Type Ia supernovae. Dynamical models of the dark energy, quintessence, are then described, as well as how they relate to theories of gravity and particle physics. The basic theory of structure formation via gravitational instability is then reviewed. Finally, we describe new observational probes of the large-structure of the universe, and how they constrain cosmological parameters.

astro-ph↗

arXiv2001

The QMAP and MAT/TOCO Experiments for Measuring Anisotropy in the Cosmic Microwave Background

We describe two related experiments that measured the anisotropy in the cosmic microwave background (CMB). QMAP was a balloon-borne telescope that flew twice in 1996, collecting data on degree angular scales with an array of six high electron mobility transistor-based amplifiers (HEMTs). QMAP was the first experiment to use an interlocking scan strategy to directly produce high signal-to-noise CMB maps. The QMAP gondola was then refit for ground based work as the MAT/TOCO experiment. Observations were made from 5200 m on Cerro Toco in Northern Chile in 1997 and 1998 using time-domain beam synthesis. MAT/TOCO was the first experiment to see both the rise and fall of the CMB angular spectrum, thereby localizing the position of the first peak to l_{peak}=216 +/- 14. In addition to describing the instruments, we discuss the data selection methods, checks for systematic errors, and we compare the MAT/TOCO results to those from recent experiments. We also correct the data to account for an updated calibration and a small contribution from foreground emission. We find the amplitude of the first peak for l between 160 and 240 to be T_{peak}=80.9 +/- 3.4 +/- 5.1 uK, where the first error is statistical and the second is from calibration.

astro-ph↗

arXiv2000

Galactic Observations at 31, 42 and 144~GHz with the Mobile Anisotropy Telescope

We present multi-frequency maps of a portion of the Galactic Plane centered on a declination of -60 degrees with resolutions ranging from 0.2 to 0.9 degrees. The maps are optimized to detect unresolved source emission and are cross-calibrated against the planet Jupiter. We discuss six millimeter-bright regions, three of which are visible in all bands, and list measured flux densities. Variability is limited to less than 3.8% for all sources seen at 31 and 42 GHz and less than 10% at 144 GHz. Fractional polarization limits smaller than 0.08 are measured for all sources seen at 31 and 42 GHz. No fractional polarization limits are reported at 144 GHz.

astro-ph↗

arXiv1999

A Measurement of the Angular Power Spectrum of the CMB from l = 100 to 400

We report on a measurement of the angular spectrum of the CMB between $l\approx 100$ and $l\approx 400$ made at 144 GHz from Cerro Toco in the Chilean altiplano. When the new data are combined with previous data at 30 and 40 GHz, taken with the same instrument observing the same section of sky, we find: 1) a rise in the angular spectrum to a maximum with $δT_l \approx 85~μ$K at $l\approx 200$ and a fall at $l>300$, thereby localizing the peak near $l\approx 200$; and 2) that the anisotropy at $l\approx 200$ has the spectrum of the CMB.

astro-ph↗