COMAP Early Science. VII. Prospects for CO Intensity Mapping at Reionization

et al. 2022

ApJ

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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 k = 0.051–0.62 Mpc−1, we estimate P CO(k) = −2. 7 ± 1.7 × 104 μK2 Mpc3, the first direct 3D constraint on the clustering component of the CO(1–0) power spectrum in the literature.

Section: Introductionmentioning

confidence: 99%

COMAP Early Science. IV. Power Spectrum Methodology and Results

Ihle

Borowska

et al. 2022

ApJ

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“…Key requirements for the instrument have been informed by continuing theoretical simulations (Breysse et al 2022;Chung et al 2022), while the pipeline analysis (Foss et al 2022) and science data processing (Ihle et al 2022;Rennie et al 2022) have been crucial in evaluating performance, detecting problems, and verifying fixes. Since the first season of observations, several improvements have been made, such as upgrading LNA modules, installing two-stage polarizers on all feeds, and repairing faulty components.…”

Section: Discussionmentioning

confidence: 99%

COMAP Early Science. II. Pathfinder Instrument

Lamb

Woody

et al. 2022

ApJ

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Line intensity mapping (LIM) is a new technique for tracing the global properties of galaxies over cosmic time. Detection of the very faint signals from redshifted carbon monoxide (CO), a tracer of star formation, pushes the limits of what is feasible with a total-power instrument. The CO Mapping Project Pathfinder is a first-generation instrument aiming to prove the concept and develop the technology for future experiments, as well as delivering early science products. With 19 receiver channels in a hexagonal focal plane arrangement on a 10.4 m antenna and an instantaneous 26–34 GHz frequency range with 2 MHz resolution, it is ideally suited to measuring CO (J = 1–0) from z ∼ 3. In this paper we discuss strategies for designing and building the Pathfinder and the challenges that were encountered. The design of the instrument prioritized LIM requirements over those of ancillary science. After a couple of years of operation, the instrument is well understood, and the first year of data is already yielding useful science results. Experience with this Pathfinder will guide the design of the next generations of experiments.

“…In addition to our fiducial model, which, as we noted toward the end of Section 2.2, is a conservative estimate by the very nature of data-driven priors based on direct-detection measurements, we also consider the signal estimate derived from the empirical CO model of Keating et al (2020a). This model, which we label "Li et al (2016)- Keating et al (2020a)" to distinguish it from the COPSS-based shot-noise estimate also calculated by Keating et al (2020a), is also one of the primary models that Breysse et al (2022a) use for COMAP forecasts beyond the Pathfinder. The model borrows the general approach of Li et al (2016), which composes the simulationand data-driven halo mass-SFR connection from Behroozi et al (2013aBehroozi et al ( , 2013b with an empirical IR-CO luminosity fit but uses newer (albeit exclusively local) IR-CO correlation fits from Kamenetzky et al (2016).…”

Section: Current Predictions For Detection Significancementioning

confidence: 99%

“…However, our priors around the CO model are fairly loose, whereas some real-world analyses like those of Keating et al (2020a) or some Fisher analyses like those of Breysse et al (2022a) make stronger assumptions about the shape of the L(M h ) relation-which then completely determines at least the line bias -and constrain only the overall normalization of L(M h ). In our Fisher forecastʼs parameter space this would be equivalent to imposing very narrow priors on b.…”

Section: Current Predictions For Detection Significancementioning

confidence: 99%

“…Other papers associated with these results 17 describe the instrument (Lamb et al 2022), data processing and mapmaking procedures (Foss et al 2022), and power spectrum methodology and results (Ihle et al 2022). This paper aims to convert these measurements into astrophysical inferences and consider forecasts for the remainder of the initial 5 yr Pathfinder campaign, with a separate paper by Breysse et al (2022a) considering potential realizations of COMAP beyond the Pathfinder.…”

Section: Introductionmentioning

confidence: 99%

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COMAP Early Science. V. Constraints and Forecasts at z ∼ 3

Chung

Breysse

et al. 2022

ApJ

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We present the current state of models for the z ∼ 3 carbon monoxide (CO) line intensity signal targeted by the CO Mapping Array Project (COMAP) Pathfinder in the context of its early science results. Our fiducial model, relating dark matter halo properties to CO luminosities, informs parameter priors with empirical models of the galaxy–halo connection and previous CO (1–0) observations. The Pathfinder early science data spanning wavenumbers k = 0.051–0.62 Mpc−1 represent the first direct 3D constraint on the clustering component of the CO (1–0) power spectrum. Our 95% upper limit on the redshift-space clustering amplitude A clust ≲ 70 μK2 greatly improves on the indirect upper limit of 420 μK2 reported from the CO Power Spectrum Survey (COPSS) measurement at k ∼ 1 Mpc−1. The COMAP limit excludes a subset of models from previous literature and constrains interpretation of the COPSS results, demonstrating the complementary nature of COMAP and interferometric CO surveys. Using line bias expectations from our priors, we also constrain the squared mean line intensity–bias product, Tb 2 ≲ 50 μK2, and the cosmic molecular gas density, ρ H2 < 2.5 × 108 M ⊙ Mpc−3 (95% upper limits). Based on early instrument performance and our current CO signal estimates, we forecast that the 5 yr Pathfinder campaign will detect the CO power spectrum with overall signal-to-noise ratio of 9–17. Between then and now, we also expect to detect the CO–galaxy cross-spectrum using overlapping galaxy survey data, enabling enhanced inferences of cosmic star formation and galaxy evolution history.