We present the detailed science case, and brief descriptions of the telescope design, site, and first light instrument plans for a new ultra-wide field submillimeter observatory, CCAT-prime, that we are constructing at a 5600 m elevation site on Cerro Chajnantor in northern Chile. Our science goals are to study star and galaxy formation from the epoch of reionization to the present, investigate the growth of structure in the Universe, improve the precision of B-mode CMB measurements, and investigate the interstellar medium and star formation in the Galaxy and nearby galaxies through spectroscopic, polarimetric, and broadband surveys at wavelengths from 200 m to 2 mm. These goals are realized with our two first light instruments, a large field-of-view (FoV) bolometer-based imager called Prime-Cam (that has both camera and an imaging spectrometer modules), and a multi-beam submillimeter heterodyne spectrometer, CHAI. CCAT-prime will have very high surface accuracy and very low system emissivity, so that combined with its wide FoV at the unsurpassed CCAT site our telescope/instrumentation combination is ideally suited to pursue this science. The CCAT-prime telescope is being designed and built by Vertex Antennentechnik GmbH. We expect to achieve first light in the spring of 2021.
Due to the recent dramatic technological advances, infrared interferometry can now be applied to new classes
of objects, resulting in exciting new science prospects, for instance, in the area of high-mass star formation.
Although extensively studied at various wavelengths, the process through which massive stars form is still only
poorly understood. For instance, it has been proposed that massive stars might form like low-mass stars by mass
accretion through a circumstellar disk/envelope, or otherwise by coalescence in a dense stellar cluster. Therefore,
clear observational evidence, such as the detection of disks around high-mass young stellar objects (YSOs), is
urgently needed in order to unambiguously identify the formation mode of the most massive stars.
After discussing the technological challenges which result from the special properties of these objects, we
present first near-infrared interferometric observations, which we obtained on the massive YSO IRAS 13481-6124
using VLTI/AMBER infrared long-baseline interferometry and NTT speckle interferometry. From our extensive
data set, we reconstruct a model-independent aperture synthesis image which shows an elongated structure with
a size of ~ 13 x 19 AU, consistent with a disk seen under an inclination of - 45°. The measured wavelengthdependent
visibilities and closure phases allow us to derive the radial disk temperature gradient and to detect a
dust-free region inside of 9.5 AU from the star, revealing qualitative and quantitative similarities with the disks
observed in low-mass star formation. In complementary mid-infrared Spitzer and sub-millimeter APEX imaging
observations we detect two bow shocks and a molecular outflow, which are oriented perpendicular to the disk
plane and indicate the presence of a bipolar outflow emanating from the inner regions of the system.
We report on developments of submillimeter heterodyne arrays for high resolution spectroscopy with APEX. Shortly, we will operate
state-of-the-art instruments in all major atmospheric windows accessible from Llano de Chajnantor. CHAMP+, a dual-color 2×7 element heterodyne array for operation in the 450 μm and 350 μm atmospheric windows is in operation since late 2007. With its
state-of-the-art SIS detectors and wide tunable local oscillators, its cold optics with single sideband filters and with 3 GHz of processed IF bandwidth per pixel, CHAMP+ does provide outstanding observing capabilities. The Large APEX sub-Millimeter Array (LAsMA) is in the final design phase, with an installation goal in 2009. The receiver will operate 7 and 19 pixels in the lower submillimeter windows, 285-375 GHz and 385-520 GHz, respectively. The front-ends are served by an array of digital wideband Fast Fourier Transform spectrometers currently processing up to 32×1.5 (optionally 1.8) GHz of bandwidth. For CHAMP+, we process 2.8 GHz of instantaneous bandwidth (in 16.4 k channels) for each of the 14 pixels.
APEX, the Atacama Pathfinder Experiment, has been successfully commissioned and is in operation now. This novel submillimeter telescope is located at 5107 m altitude on Llano de Chajnantor in the Chilean High Andes, on what is considered one of the world's outstanding sites for submillimeter astronomy. The primary reflector with 12 m diameter has been carefully adjusted by means of holography. Its surface smoothness of 17-18 μm makes APEX suitable for observations up to 200 μm, through all atmospheric submm windows accessible from the ground.
With ESO and Onsala Space Observatory as partners, the Max-Planck-Institut for Radioastronomie (MPIfR) is building a submillimeter telescope of 12 m diameter (APEX), to be placed on the ALMA site (Chajnantor) in Chile. The telescope will be a modified copy of that ALMA prototype antenna, which has been designed by Vertex. First light is foreseen for 2003. As a result of the excellent atmospheric conditions of the site, APEX will offer unique opportunities for submm astronomy in the southern hemisphere. Many kinds of astronomical reseach projects benefit from large format bolometer arrays, especially the search for early galaxies and QSOs at very high redshifts. Designed for this purpose, LABOCA, the large bolometer camera, will operate at a wavelength of 870 μm and is planned to be operational soon after first light of APEX.
A 16-element SIS heterodyne array for operation in the 625 micrometer atmospheric window is under development at the MPIfR. The array consists of 2 X 8 elements with closest feasible spacing of the pixels on the sky ((root)2 (DOT) (Theta) <SUB>mb</SUB>). The L.O. tuning range covers the astronomically important CI and the CO(4-3) transitions, and an IF bandwidth of 2 GHz (1200 kms<SUP>-1</SUP>) will permit mapping of extragalactic systems. For best system sensitivity the design allows for cold optics ( 15K) and single-sideband operation. The frontend will be linked to a flexible autocorrelator, with a maximum bandwidth of 2 GHz (2048 channels) for each of the 16 modules. In the high-resolution mode, 500 MHz of bandwidth can be operated with 8192 channels of 61 kHz spectral resolution. System components are currently undergoing final integration and critical evaluation in our laboratories. First astronomical commissioning is scheduled for later this year. The sensitivity expected with CHAMP, for e.g. carbon studies, will be unparalleled. With the full array in SSB operation the mapping speed will be enhanced by a factor of 50 - 100 compared to current single-pixel detectors.