2 research outputs found
COMAP Early Science: IV. Power Spectrum Methodology and Results
We present the power spectrum methodology used for the first-season COMAP
analysis, and assess the quality of the current data set. The main results are
derived through the Feed-feed Pseudo-Cross-Spectrum (FPXS) method, which is a
robust estimator with respect to both noise modeling errors and experimental
systematics. We use effective transfer functions to take into account the
effects of instrumental beam smoothing and various filter operations applied
during the low-level data processing. The power spectra estimated in this way
have allowed us to identify a systematic error associated with one of our two
scanning strategies, believed to be due to residual ground or atmospheric
contamination. We omit these data from our analysis and no longer use this
scanning technique for observations. We present the power spectra from our
first season of observing and demonstrate that the uncertainties are
integrating as expected for uncorrelated noise, with any residual systematics
suppressed to a level below the noise. Using the FPXS method, and combining
data on scales we estimate , the first direct 3D
constraint on the clustering component of the CO(1-0) power spectrum in the
literature.Comment: Paper 4 of 7 in series. 18 pages, 11 figures, as accepted in Ap
A Model of Spectral Line Broadening in Signal Forecasts for Line-intensity Mapping Experiments
Line-intensity mapping observations will find fluctuations of integrated line
emission are attenuated by varying degrees at small scales due to the width of
the line emission profiles. This attenuation may significantly impact estimates
of astrophysical or cosmological quantities derived from measurements. We
consider a theoretical treatment of the effect of line broadening on both the
clustering and shot-noise components of the power spectrum of a generic
line-intensity power spectrum using a halo model. We then consider possible
simplifications to allow easier application in analysis, particularly in the
context of inferences that require numerous, repeated, fast computations of
model line-intensity signals across a large parameter space. For the CO Mapping
Array Project (COMAP) and the CO(1-0) line-intensity field at serving
as our primary case study, we expect a attenuation of the
spherically averaged power spectrum on average at relevant scales of
- Mpc, compared to for the interferometric
Millimetre-wave Intensity Mapping Experiment (mmIME) targeting shot noise from
CO lines at - at scales of Mpc. We also consider
the nature and amplitude of errors introduced by simplified treatments of line
broadening, and find that while an approximation using a single effective
velocity scale is sufficient for spherically-averaged power spectra, a more
careful treatment is necessary when considering other statistics such as higher
multipoles of the anisotropic power spectrum or the voxel intensity
distribution.Comment: 24 pages + appendix and bibliography (33 pages total), 16 figures, 2
tables; accepted for publication in Ap