CFRP truss for the CCAT 25 m diameter submillimeter-wave telescope

CCAT will be a 25 m diameter submillimeter-wave telescope that will operate inside a dome located on Cerro Chajnantor in the Atacama Desert. The telescope must have high aperture efficiency at a wavelength of 350 microns and good performance out to a wavelength of 200 microns. A conceptual design for a carbon fiber reinforced plastic (CFRP) truss and primary reflector support truss has been developed. This design yields a telescope with a net �½ wave front error of <10 microns using a lookup table to adjust the segment actuators to compensate for gravitational deflections. Minor corrections may be required to compensate for the expected 20 C temperature excursions. These can be handled using a coarse lookup table

The Cornell Caltech Atacama Telescope status and technical progress

Five partners have currently joined a Consortium to develop the Cornell Caltech Atacama Telescope (CCAT.) Included are Cornell University, the California Institute of Technology (Caltech), the University of Colorado at Boulder, the United Kingdom as represented by the Astronomy Technology Centre (ATC), and Canada as represented by the Universities of British Columbia and Waterloo. This consortium has continued work toward the design of the telescope and instrumentation, pursued fund raising, and further developed the science case for CCAT. An Engineering Design Phase is being planned for 2009-2011 with construction planned to begin shortly thereafter. CCAT continues as a wide field (20 arc min) FOV telescope operating from a shortest wavelength of 200µ. Testing has continued near the summit of Cerro Chajnantor in the Atacama Region of Chile above 5600 meters altitude and data indicates significantly lower water vapor in the seeing column than measured at the ALMA site on the plateau below. Work over the past two years has included research on manufacturing methods for optical segments, extensive study of mirror alignment sensing and control techniques, additional concepts for major structures, and further development of instrumentation

Measurements of Salinity in the Coastal Ocean: A Review of Requirements and Technologies

Salinity, a measure of the dissolved salts in seawater, is a fundamental property of seawater and basic to understanding biological and physical processes in coastal waters. In the open ocean long term salinity measurements are identified as necessary to understand global climate studies, hydrological cycle, and circulation. In the coastal oceans, information on salinity is critical to understanding biological effects on ecosystem function such as disease, nursery grounds, or harmful algal blooms and on physical processes such as freshwater runoff estuarine mixing, and coastal currents. While the importance of salinity is recognized, little attention has been given to making routine measurements as to the location and frequency of such measurements. These issues were addressed in a workshop concerned with salinity measurements in coastal oceans, requirements for such, and measurment technology

Radio Sources from a 31 GHz Sky Survey with the Sunyaev-Zel'dovich Array

We present the first sample of 31-GHz selected sources to flux levels of 1 mJy. From late 2005 to mid 2007, the Sunyaev-Zel'dovich Array (SZA) observed 7.7 square degrees of the sky at 31 GHz to a median rms of 0.18 mJy/beam. We identify 209 sources at greater than 5 sigma significance in the 31 GHz maps, ranging in flux from 0.7 mJy to ~200 mJy. Archival NVSS data at 1.4 GHz and observations at 5 GHz with the Very Large Array are used to characterize the sources. We determine the maximum-likelihood integrated source count to be N(>S) = (27.2 +- 2.5) deg^-2 x (S_mJy)^(-1.18 +- 0.12) over the flux range 0.7 - 15 mJy. This result is significantly higher than predictions based on 1.4-GHz selected samples, a discrepancy which can be explained by a small shift in the spectral index distribution for faint 1.4-GHz sources. From comparison with previous measurements of sources within the central arcminute of massive clusters, we derive an overdensity of 6.8 +- 4.4, relative to field sources.Comment: 13 pages, 5 figure

The Cornell Caltech Atacama Telescope status and technical progress

Five partners have currently joined a Consortium to develop the Cornell Caltech Atacama Telescope (CCAT.) Included are Cornell University, the California Institute of Technology (Caltech), the University of Colorado at Boulder, the United Kingdom as represented by the Astronomy Technology Centre (ATC), and Canada as represented by the Universities of British Columbia and Waterloo. This consortium has continued work toward the design of the telescope and instrumentation, pursued fund raising, and further developed the science case for CCAT. An Engineering Design Phase is being planned for 2009-2011 with construction planned to begin shortly thereafter. CCAT continues as a wide field (20 arc min) FOV telescope operating from a shortest wavelength of 200µ. Testing has continued near the summit of Cerro Chajnantor in the Atacama Region of Chile above 5600 meters altitude and data indicates significantly lower water vapor in the seeing column than measured at the ALMA site on the plateau below. Work over the past two years has included research on manufacturing methods for optical segments, extensive study of mirror alignment sensing and control techniques, additional concepts for major structures, and further development of instrumentation

Atmospheric phase correction using CARMA-PACS: high angular resolution observations of the FU Orionis star PP 13S*

We present 0".15 resolution observations of the 227 GHz continuum emission from the circumstellar disk around the FU Orionis star PP 13S*. The data were obtained with the Combined Array for Research in Millimeter-wave Astronomy (CARMA) Paired Antenna Calibration System (C-PACS), which measures and corrects the atmospheric delay fluctuations on the longest baselines of the array in order to improve the sensitivity and angular resolution of the observations. A description of the C-PACS technique and the data reduction procedures are presented. C-PACS was applied to CARMA observations of PP 13S*, which led to a factor of 1.6 increase in the observed peak flux of the source, a 36% reduction in the noise of the image, and a 52% decrease in the measured size of the source major axis. The calibrated complex visibilities were fitted with a theoretical disk model to constrain the disk surface density. The total disk mass from the best-fit model corresponds to 0.06 M_⊙, which is larger than the median mass of a disk around a classical T Tauri star. The disk is optically thick at a wavelength of 1.3 mm for orbital radii less than 48 AU. At larger radii, the inferred surface density of the PP 13S* disk is an order of magnitude lower than that needed to develop a gravitational instability

CARMA Measurements of the Sunyaev-Zel'dovich Effect in RXJ1347.5-1145

We demonstrate the Sunyaev-Zel'dovich (SZ) effect imaging capabilities of the Combined Array for Research in Millimeter-wave Astronomy (CARMA) by presenting an SZ map of the galaxy cluster RXJ1347.5-1145. By combining data from multiple CARMA bands and configurations, we are able to capture the structure of this cluster over a wide range of angular scales, from its bulk properties to its core morphology. We find that roughly 9% of this cluster's thermal energy is associated with sub-arcminute-scale structure imparted by a merger, illustrating the value of high-resolution SZ measurements for pursuing cluster astrophysics and for understanding the scatter in SZ scaling relations. We also find that the cluster's SZ signal is lower in amplitude than suggested by a spherically-symmetric model derived from X-ray data, consistent with compression along the line of sight relative to the plane of the sky. Finally, we discuss the impact of upgrades currently in progress that will further enhance CARMA's power as an SZ imaging instrument.Comment: 8 pages, 6 figure

Joint analysis of X-ray and Sunyaev Zel'dovich observations of galaxy clusters using an analytic model of the intra-cluster medium

We perform a joint analysis of X-ray and Sunyaev Zel'dovich (SZ) effect data using an analytic model that describes the gas properties of galaxy clusters. The joint analysis allows the measurement of the cluster gas mass fraction profile and Hubble constant independent of cosmological parameters. Weak cosmological priors are used to calculate the overdensity radius within which the gas mass fractions are reported. Such an analysis can provide direct constraints on the evolution of the cluster gas mass fraction with redshift. We validate the model and the joint analysis on high signal-to-noise data from the Chandra X-ray Observatory and the Sunyaev-Zel'dovich Array for two clusters, Abell 2631 and Abell 2204.Comment: ApJ in pres