The Combined Array for Research in Millimeter-wave Astronomy (CARMA) is an array of 23 radio telescopes located at Cedar Flat, in the Inyo Mountains of California. The array is heterogeneous, consisting of six 10-m telescopes belonging to Caltech, nine 6-m telescopes from the Berkeley-Illinois-Maryland Association, and eight 3.5-m telescopes of The University of Chicago. Not all telescopes currently have the capability to observe at the same wavelength or frequency bandpasses simultaneously. The goal of being able to outfit all telescopes with receivers capable of observing at the same bandpass at the same time will soon be realized. A collaboration between Dr. John Carpenter of the California Institute of Technology and Dr. John Carlstrom of The University of Chicago will develop the digital correlators and receivers to fully integrate the CARMA telescopes into a single array that cross-correlates the signals from all 23 antennas simultaneously over the full 8 GHz IF bandwidth of the CARMA receivers. This will provide significantly enhanced observing capability and will enable new discoveries in cosmology (especially the study of galaxy clusters and the Sunyaev-Zel'dovich effect) and star formation (through the study of the chemistry and kinematics of molecular gas in star-forming regions). This work is being funded by NSF's Major Research Instrumentation program though the Division of Astronomical Sciences.
This award was used to enhance the capability of the Combined Array for Millimeter Astronomy (CARMA) located at Cedar Flat, near White Mountain in California. There are eight 3.5 m, nine 6 m, and six 10 m telescopes. The award was used to add state of the art receivers sensitive to centimenter-wave emission. The receivers were built at the University of Chicago, primarily by graduate students, in particular Zubair Abdulla, shown in the attached figure. The receivers are cooled to 10 degrees above absolute zero (10 Kelvin) to lower their noise. The primary science goal is to image the spectral distortion in the cosmic microwave background cause by its interaction with the hot gas associated with galaxy clusters. The cosmic microwave background is the fossil light from the big bang, which has been traveling to us for nearly 14 billion years. Galaxy clusters are the largest objects the universe has produced, with masses exceeding a thousand trillion times the mass of our sun. About 80% of this tremendous mass is dark matter, while most of the cluster's ordinary matter is contained in a hot 100 million degree gas. The galaxies (not shown here) account for only a small fraction of the mass, although they are the only component visible at optical wavelengths. The hot gas interacts with the cosmic microwave background causing a small distortion, which appears as a shadow at cm-wavelengths, known as the Sunyaev-Zel'dovich effect. By adding sensitive cm-wave receivers to CARMA, we are able to make detailed images of the Sunyaev-Zel'dovich effect. This data allows us to investigate the details of the galaxy cluster in a unique and complementary way to that done at other wavelengths. The figure shows the first CARMA 23 telescope arrray imaging of the Sunyaev-Zel'dovich effect, directed at the massive galaxy cluster MS0735. The Sunyaev-Zel'dovich imaging (blue in the figure) reveals the total energy and distribution of the hot gas. In addition the figure also shows the x-ray emission of the hot gas (pink), which is sensitive to the density of the gas, as well as the bright radio emission (green), which traces the very high energy jets of gas driven from a black hole in the central galaxy (much too small to be imaged). Understanding the structure of these most massive objects requires such multiwavelength observations and enables fundamental tests of the evolution of the universe.
