Line-intensity mapping (LIM) of emission from star-forming galaxies can be used to measure the baryon acoustic oscillation (BAO) scale as far back as the epoch of reionization. This provides a ...standard cosmic ruler to constrain the expansion rate of the Universe at redshifts which cannot be directly probed otherwise. In light of growing tension between measurements of the current expansion rate using the local distance ladder and those inferred from the cosmic microwave background, extending the constraints on the expansion history to bridge between the late and early Universe is of paramount importance. Using a newly derived methodology to robustly extract cosmological information from LIM, which minimizes the inherent degeneracy with unknown astrophysics, we show that present and future experiments can gradually improve the measurement precision of the expansion rate history, ultimately reaching percent-level constraints on the BAO scale. Specifically, we provide detailed forecasts for the SPHEREx satellite, which will target the Hα and Lyman-α lines, for a near-future stage-2 experiment targeting CII, and for the ground-based COMAP instrument-as well as a future stage-3 experiment-that will target the CO rotational lines. Besides weighing in on the so-called Hubble tension, reliable LIM cosmic rulers can enable wide-ranging tests of dark matter, dark energy, and modified gravity.
Abstract
The study of molecular gas is crucial for understanding star formation, feedback and the broader ecosystem of a galaxy as a whole. However, we have limited understanding of its physics and ...distribution in all but the nearest galaxies. We present a new technique for studying the composition and distribution of molecular gas in high-redshift galaxies inaccessible to existing methods. Our proposed approach is an extension of carbon monoxide intensity mapping methods, which have garnered significant experimental interest in recent years. These intensity mapping surveys target the 115 GHz 12CO (1–0) line, but also contain emission from the substantially fainter 110 GHz 13CO (1–0) transition. The method leverages the information contained in the 13CO line by cross-correlating pairs of frequency channels in an intensity mapping survey. Since 13CO is emitted from the same medium as the 12CO, but saturates at a much higher column density, this cross-correlation provides valuable information about both the gas density distribution and isotopologue ratio, inaccessible from the 12CO alone. Using a simple model of these molecular emission lines, we show that a future intensity mapping survey can constrain the abundance ratio of these two species and the fraction of emission from optically thick regions to order ∼30 per cent. These measurements cannot be made by traditional CO observations, and consequently the proposed method will provide unique insight into the physics of star formation, feedback and galactic ecology at high redshifts.
We present a study of the feasibility of an intensity-mapping survey targeting the 115 GHz CO(1-0) rotational transition at z ~ 3. We consider four possible models and estimate the spatial and ...angular power spectra of CO fluctuations predicted by each of them. The frequency bandwidths of most proposed CO intensity mapping spectrographs are too small to use the Limber approximation to calculate the angular power spectrum, so we present an alternative method for calculating the angular power spectrum. The models we consider span two orders of magnitude in signal amplitude, so there is a significant amount of uncertainty in the theoretical predictions of this signal. We then consider a parametrized set of hypothetical spectrographs designed to measure this power spectrum and predict the signal-to-noise ratios (SNRs) expected under these models. With the spectrographs we consider we find that three of the four models give an SNR greater than 10 within one year of observation. We also study the effects on SNR of varying the parameters of the survey in order to demonstrate the importance of carefully considering survey parameters when planning such an experiment.
Observing AGN feedback with CO intensity mapping Breysse, Patrick C; Alexandroff, Rachael M
Monthly Notices of the Royal Astronomical Society,
11/2019, Letnik:
490, Številka:
1
Journal Article
Recenzirano
Odprti dostop
ABSTRACT Current models of galaxy formation require star formation in high-mass galaxies to be limited by poorly understood mechanisms of quasar feedback. Feedback processes can be studied by ...examining the molecular gas content of AGN hosts through the CO rotational ladder, but the complexity of these observations means that current data are limited to only extremely CO-bright objects. Upcoming CO intensity mapping experiments offer an opportunity for a less biased probe of quasar feedback. By correlating intensity maps with spectroscopic AGN surveys, we can obtain a measurement of the mean CO luminosity of a large population of quasars simultaneously. We show that experiments like COMAP, CCAT-prime, and CONCERTO have enough sensitivity to detect this cross-correlation if existing AGN observations are representative of the whole population, and to place interesting upper limits if they are not. Future surveys will be able to increase the precision of these measurements by orders of magnitude, allowing detailed studies of quasar properties across a wide range of cosmic history.
Canceling Out Intensity Mapping Foregrounds Breysse, Patrick C; Anderson, Christopher J; Berger, Philippe
Physical review letters,
12/2019, Letnik:
123, Številka:
23
Journal Article
Recenzirano
Intensity mapping of the 21 cm line has arisen as a powerful probe of the high-redshift Universe, but its potential is limited by extremely bright foregrounds and high source confusion. We propose a ...new analysis which can help solve both problems. From the combination of an intensity map with an overlapping galaxy survey, we construct a new one-point statistic which is unbiased by foregrounds and contains information left out of conventional analyses. We show that our method can measure the HI mass function with unprecedented precision using observations similar to recent 21 cm detections.
Abstract
In the next few years, intensity-mapping surveys that target lines such as CO, Lyα and C ii stand to provide powerful probes of high-redshift astrophysics. However, these line emissions are ...highly non-Gaussian, and so the typical power-spectrum methods used to study these maps will leave out a significant amount of information. We propose a new statistic, the probability distribution of voxel intensities, which can access this extra information. Using a model of a CO intensity map at z ∼ 3 as an example, we demonstrate that this voxel intensity distribution (VID) provides substantial constraining power beyond what is obtainable from the power spectrum alone. We find that a future survey is similar to the planned CO Mapping Array Pathfinder (COMAP). Full experiment could constrain the CO luminosity function to the order of ∼10 per cent. We also explore the effects of contamination from continuum emission, interloper lines and gravitational lensing on our constraints and find that the VID statistic retains significant constraining power even in pessimistic scenarios.
We demonstrate how cosmic star formation history can be measured with one-point statistics of carbon-monoxide intensity maps. Using a P(D) analysis, the luminosity function of CO-emitting sources can ...be inferred from the measured one-point intensity PDF. The star formation rate density (SFRD) can then be obtained, at several redshifts, from the CO luminosity density. We study the effects of instrumental noise, line foregrounds, and target redshift, and obtain constraints on the CO luminosity density of the order of 10 per cent. We show that the SFRD uncertainty is dominated by that of the model connecting CO luminosity and star formation. For pessimistic estimates of this model uncertainty, we obtain an error of the order of 50 per cent on SFRD for surveys targeting redshifts between two and seven with reasonable noise and foregrounds included. However, comparisons between intensity maps and galaxies could substantially reduce this model uncertainty. In this case, our constraints on SFRD at these redshifts improve to roughly 5 − 10 per cent, which is highly competitive with current measurements.
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