Cornell Caltech Atacama Telescope Research Articles

Demonstrating the feasibility of line intensity mapping using mock data of galaxy clustering from simulations

Visbal & Loeb (2010) have shown that it is possible to measure theclustering of galaxies by cross correlating the cumulative emissionfrom two different spectral lines which originate at the sameredshift. Through this cross correlation, one can study galaxieswhich are too faint to be individually resolved. This technique, knownas intensity mapping, is a promising probe of the global properties ofhigh redshift galaxies. Here, we test the feasibility of suchmeasurements with synthetic data generated from cosmological darkmatter simulations. We use a simple prescription for associatinggalaxies with dark matter halos and create a realization of emittedradiation as a function of angular position and wavelength over apatch of the sky. This is then used to create synthetic data forthree different hypothetical instruments, one aboard the SpaceInfrared Telescope for Cosmology and Astrophysics (SPICA), anotherconsisting of a pair of ground based radio telescopes designed tomeasure the CO(1-0) and CO(2-1) emission lines, and one on the CornellCaltech Atacama Telescope (CCAT). We find that the line cross powerspectrum can be measured accurately from the synthetic data witherrors consistent with the analytical prediction of Visbal & Loeb(2010). Removal of astronomical backgrounds and masking bright lineemission from foreground contaminating galaxies do not preventaccurate cross power spectrum measurements.

Measuring the 3D clustering of undetected galaxies through cross correlation of their cumulative flux fluctuations from multiple spectral lines

We discuss a method for detecting the emission from high redshiftgalaxies by cross correlating flux fluctuations from multiple spectrallines. If one can fit and subtract away the continuum emission with asmooth function of frequency, the remaining signal containsfluctuations of flux with frequency and angle from line emittinggalaxies. Over a particular small range of observed frequencies,these fluctuations will originate from sources corresponding to aseries of different redshifts, one for each emission line. It ispossible to statistically isolate the fluctuations at a particularredshift by cross correlating emission originating from the sameredshift, but in different emission lines. This technique will allowdetection of clustering fluctuations from the faintest galaxies whichindividually cannot be detected, but which contribute substantially tothe total signal due to their large numbers. We describe thesefluctuations quantitatively through the line cross power spectrum. Asan example of a particular application of this technique, we calculatethe signal-to-noise ratio for a measurement of the cross powerspectrum of the OI(63 μm) and OIII(52 μm) fine structure lineswith the proposed Space Infrared Telescope for Cosmology andAstrophysics (SPICA). We find that the cross power spectrum can bemeasured beyond a redshift of z = 8. Such observations couldconstrain the evolution of the metallicity, bias, and duty cycle offaint galaxies at high redshifts and may also be sensitive to thereionization history through its effect on the minimum mass ofgalaxies. As another example of this technique, we calculate thesignal-to-noise ratio for the cross power spectrum of CO line emissionmeasured with a large ground based telescope like the Cornell CaltechAtacama Telescope (CCAT) and 21-cm radiation originating from hydrogenin galaxies after reionization with an interferometer similar in scaleto the Murchison Widefield Array (MWA), but optimized forpost-reionization redshifts.

Atmospheric Transmission at Dome C between 0 and 10 THz

We present model calculations of the atmospheric transmission for DOME C in Antarctica for frequencies up to 10THz (30 μm) using the forward model MOLIERE-5. Measurements of precipitable water vapor (pwv), obtained by the SUMMIT radiometer installed at the Concordia station during 2008 and working at a wavelength of 200μm, are translated into atmospheric transmission using MOLIERE. Quartiles of transmission, calculated from 200μm data are extrapolated to 350 μm and compared to the CCAT (Cornell-Caltech Atacama Telescope) site in Chile. It turns out that for 25% of the time at DOME C (CCAT), the transmission is around 20% (5%) at 200μm. This corresponds to a pwv of 0.18mm for DOME C. At 350μm, for 50% of time at DOME C (CCAT) the transmission is around 55% (25%). This corresponds to a pwv of 0.22mm for DOME C. These results show that DOME C is one of the best observing sites on Earth for submm-astronomy with respect to high atmospheric transmission over long time periods

Simulations of the Sunyaev-Zel'dovich effect from quasars

Quasar feedback has most likely a substantial but only partially understood impact on the formation of structure in the universe. A potential direct probe of this feedback mechanism is the Sunyaev-Zel'dovich (SZ) effect: energy emitted from quasar heats the surrounding intergalactic medium and induces a distortion in the microwave background radiation passing through the region. Here, we examine the formation of such hot quasar bubbles using a cosmological hydrodynamic simulation which includes a self-consistent treatment of black hole growth and associated feedback, along with radiative gas cooling and star formation. From this simulation, we construct microwave maps of the resulting SZ effect around black holes with a range of masses and redshifts. The size of the temperature distortion scales approximately with black hole mass and accretion rate, with a typical amplitude up to a few micro-Kelvin on angular scales around 10 arcsec. We discuss prospects for the direct detection of this signal with current and future single-dish and interferometric observations, including Atacama Large Millimetre Array (ALMA) and Cornell Caltech Atacama Telescope (CCAT). These measurements will be challenging, but will allow us to characterize the evolution and growth of supermassive black holes and the role of their energy feedback on galaxy formation.