Cross-correlations as a cosmological carbon monoxide detector
  We present a new procedure to measure the large-scale carbon monoxide (CO)
emissions across cosmic history. As a tracer of large-scale structure (LSS),
the CO gas content as a function of redshift can be quantified by its
three-dimensional fluctuation power spectra. Furthermore, cross-correlating CO
emission with other LSS tracers offers a way to measure the emission as a
function of scale and redshift. Here we introduce the model relevant for such a
cross-correlation measurement between CO and other LSS tracers, and between
different CO rotational lines. We propose a novel use of Cosmic Microwave
Background (CMB) data and attempt to extract redshifted CO emissions embedded
in the Wilkinson Microwave Anisotropy Probe (WMAP) dataset. We cross-correlate
the all-sky WMAP7 data with LSS data sets, namely, the photometric quasar
sample and the luminous red galaxy sample from the Sloan Digital Sky Survey
Data Release 6 and 7 respectively. We are unable to detect a cross-correlation
signal with either CO(1-0) nor CO(2-1) lines, mainly due to the instrumental
noise in the WMAP data. However, we are able to rule out models more than three
times greater than our more optimistic model. We discuss the cross-correlation
signal from the thermal Sunyaev-Zeldovich effect and dust as potential
contaminants, and quantify their impact for our CO measurements. We discuss
forecasts for current CMB experiments and a hypothetical future CO focused
experiment, and propose to cross-correlate CO temperature data with the
Hobby-Eberly Telescope Dark Energy Experiment Ly-alpha-emitter sample, for
which a signal-to-noise ratio of 58 is possible.
