HI Intensity Mapping Research Articles

Modeling the Nonlinear Power Spectrum in Low-redshift H i Intensity Mapping

Abstract Neutral Hydrogen (H i) serves as a competitive tracer of the large scale structures, especially with the advent of more Intensity Mapping H i surveys. In this work, we present a simulation-based framework to forecast the H i power spectrum on non-linear scales (k ≳ 1 Mpc−1), as measured by interferometer arrays like MeerKAT in the low-redshift (z ≤ 1.0) universe. Building on a galaxy-based H i mock catalog, we meticulously consider various factors, including the emission line profiles of H i discs and some observational settings, and explore their impacts on the H i power spectrum. We find that the H i power spectrum is relatively insensitive to the profile shape of H i emission line at these scales, while showing a strong correlation with the profile width. We propose an empirical model to simulate the emission line profile width for each H i source. The resulting H i power spectrum is consistent with the results from the IllustrisTNG hydrodynamical simulation and follows the trend of the measurements obtained by MeerKAT at z ≈ 0.44, though with a significantly lower amplitude. We demonstrate how the HI abundance ΩHI and the amplitude parameter in our width model can be constrained with the MeerKAT measurements, though a strong degeneracy is uncovered. Our work shows the potential to constrain statistical properties of HI emission line profiles with future HI Intensity Mapping experiments.

The feasibility of weak lensing and 21cm intensity mapping cross-correlation measurements

ABSTRACT One of the most promising probes to complement current standard cosmological surveys is the H i intensity map, i.e. the distribution of temperature fluctuations in neutral hydrogen. In this paper we present calculations of the two-point function between HI (at redshift $z\lt 1$) and lensing convergence ($\kappa$). We also construct HI intensity maps from N-body simulations, and measure two-point functions between HI and lensing convergence. HI intensity mapping requires stringent removal of bright foregrounds, including emission from our Galaxy. The removal of large-scale radial modes during this HI foreground removal will reduce the HI-lensing cross-power spectrum signal, as radial modes are integrated to find the convergence; here we wish to characterize this reduction in signal. We find that after a simple model of foreground removal, the cross-correlation signal is reduced by $\sim$50–70 per cent; we present the angular and redshift dependence of the effect, which is a weak function of these variables. We then calculate S/N of $\kappa$HI detection, including cases with cut sky observations, and noise from radio and lensing measurements. We present Fisher forecasts based on the resulting two-point functions; these forecasts show that by measuring $\kappa \Delta {T}_\mathrm{HI}$ correlation functions in a sufficient number of redshift bins, constraints on cosmology and HI bias will be possible.

A wide-angle formulation of foreground filters for HI intensity mapping

Neutral hydrogen intensity mapping can in principle deliver rapid and large-volume cosmological surveys with exquisitely accurate redshifts that are determined directly from imaging. However, intensity maps suffer from very strong foreground contamination. Future surveys will require efficient data pipelines to remove the foregrounds and reveal the cosmological signal. It is expected that this cleaning will not remove the signal in substantial parts of the available Fourier space and that significant loss of signal due to imperfect cleaning will be confined to specific regions of Fourier space. This suggests a strategy which is useful for simplified estimates and rapid computations — i.e., to apply foreground filters that avoid the regions where loss of signal is significant. The standard Fourier-space power spectrum and foreground filters use a flat-sky approximation and thus exclude wide-angle correlations. We provide a new geometrical formulation of foreground filters in harmonic space, which naturally includes all wide-angle effects in the power spectrum. Foreground filtering leads to a loss of isotropy in Fourier space. In harmonic space this produces off-diagonal correlations. We derive analytical expressions for the generalised HI power spectrum and its cross-power with CMB lensing, for both single-dish and interferometer mode surveys. We show numerically that the off-diagonal contributions are negligible for the auto power. In the cross power, there is a non-negligible off-diagonal contribution, but only for a small interval of the largest available scales. For auto and cross power, the signal loss due to foreground avoidance decreases with increasing multipole (i.e. smaller scales), and the loss in interferometer mode is equal to, or slightly greater than, in single-dish mode. We find that the cross power in single-dish mode vanishes below a critical multipole, ℓ < ℓ 0. For an SKA-like survey, ℓ 0 ∼ 20 – 40 over redshifts z = 1 – 3. This feature is not seen in interferometer mode as the pertinent angular scales are larger than those allowed by the minimum baseline.

Constraining the growth rate on linear scales by combining SKAO and DESI surveys

In the pursuit of understanding the large-scale structure of the Universe, the synergy between complementary cosmological surveys has proven to be a powerful tool. Using multiple tracers of the large-scale structure can significantly improve the constraints on cosmological parameters. We explore the potential of combining the Square Kilometre Array Observatory (SKAO) and the Dark Energy Spectroscopic Instrument (DESI) spectroscopic surveys to enhance precision on the growth rate of cosmic structures. We employ a multi-tracer Fisher analysis to estimate precision on the growth rate when using pairs of mock surveys that are based on SKAO and DESI specifications. The pairs are at both low and high redshifts. For SKA-MID, we use the HI galaxy and the HI intensity mapping samples. In order to avoid the complexities and uncertainties at small scales, we confine the analysis to scales where linear perturbations are reliable. The consequent loss of signal in each individual survey is mitigated by the gains from the multi-tracer. After marginalising over cosmological and nuisance parameters, we find a significant improvement in the precision on the growth rate.

Eliminating polarization leakage effect for neutral hydrogen intensity mapping with deep learning

ABSTRACT The neutral hydrogen (H i) intensity mapping (IM) survey is regarded as a promising approach for cosmic large-scale structure studies. A major issue for the H i IM survey is to remove the bright foreground contamination. A key to successfully removing the bright foreground is to well control or eliminate the instrumental effects. In this work, we consider the instrumental effects of polarization leakage and use the U-Net approach, a deep learning-based foreground removal technique, to eliminate the polarization leakage effect. The thermal noise is assumed to be a subdominant factor compared with the polarization leakage for future H i IM surveys and ignored in this analysis. In this method, the principal component analysis (PCA) foreground subtraction is used as a pre-processing step for the U-Net foreground subtraction. Our results show that the additional U-Net processing could either remove the foreground residual after the conservative PCA subtraction or compensate for the signal loss caused by the aggressive PCA pre-processing. Finally, we test the robustness of the U-Net foreground subtraction technique and show that it is still reliable in the case of existing constraint error on H i fluctuation amplitude.

Gravitational waves × HI intensity mapping: cosmological and astrophysical applications

Two of the most rapidly growing observables in cosmology and astrophysics are gravitational waves (GW) and the neutral hydrogen (HI) distribution.In this work, we investigate the cross-correlation between resolved gravitational wave detections and HI signal from intensity mapping (IM) experiments.By using a tomographic approach with angular power spectra, including all projection effects, we explore possible applications of the combination of the Einstein Telescope and the SKAO intensity mapping surveys.We focus on three main topics:(i) statistical inference of the observed redshift distribution of GWs;(ii) constraints on dynamical dark energy models as an example of cosmological studies;(iii) determination of the nature of the progenitors of merging binary black holes, distinguishing between primordial and astrophysical origin.Our results show that:(i) the GW redshift distribution can be calibrated with good accuracy at low redshifts, without any assumptions on cosmology or astrophysics, potentially providing a way to probe astrophysical and cosmological models;(ii) the constrains on the dynamical dark energy parameters are competitive with IM-only experiments, in a complementary way and potentially with less systematics;(iii) it will be possible to detect a relatively small abundance of primordial black holes within the gravitational waves from resolved mergers.Our results extend towards GW × IM the promising field of multi-tracing cosmology and astrophysics, which has the major advantage of allowing scientific investigations in ways that would not be possible by looking at single observables separately.

An HI intensity mapping survey with a Phased Array Feed

We report results from a neutral hydrogen (H i) intensity mapping survey conducted with a Phased Array Feed (PAF) on the Parkes telescope. The survey was designed to cover ∼ 380 deg2 over the redshift range 0.3 < z < 1 (a volume of ∼ 1.5 Gpc3) in four fields covered by the WiggleZ Dark Energy Survey. The results presented here target a narrow redshift range of 0.73 < z < 0.78 where the effect of radio frequency interference (RFI) was less problematic. The data reduction and simulation pipeline was described, with an emphasis on flagging of RFI and correction for signal loss in the data reduction process, particularly due to the foreground subtraction methodology. A cross-correlation signal was detected between the H i intensity maps and the WiggleZ redshift data, with a mean amplitude of ⟨ΔT b δ opt⟩ = 1.32 ± 0.42 mK (statistical errors only). A future Parkes cryogenic PAF is expected to detect the cross-correlation signal with higher accuracy than previously possible and allow measurement of the cosmic H i density at redshifts up to unity.

Synergies across the spectrum for particle dark matter indirect detection: how HI intensity mapping meets gamma rays

Neutral hydrogen (HI) intensity mapping traces the large-scale distribution of matter in the Universe and therefore should correlate with the gamma-ray emission originated from particle dark matter annihilation or from active galactic nuclei and star-forming galaxies, since the related processes occur in the same cosmic structures hosting HI. In this paper, we derive the cross-correlation signal between the brightness temperature of the 21-cm line emission of the HI spin-flip transition in the Universe and the unresolved gamma-ray background. Specifically, we derive forecasts for the cross-correlation signal by focussing on the opportunities offered by the combination of the Fermi-Large Area Telescope (LAT) gamma-ray sensitivity with the expectations of the HI intensity mapping measurements from future radio telescopes, for which we concentrate on the Square Kilometre Array (SKA) and MeerKAT, one of its precursors. We find that the combination of MeerKAT with the current Fermi-LAT statistics has the potential to provide a first hint of the cross-correlation signal originated by astrophysical sources, with a signal-to-noise ratio (SNR) of 3.7. With SKA Phase 1 and SKA Phase 2, the SNR is predicted to increase up to 5.7 and 8.2, respectively. The bounds on dark matter properties attainable with SKA combined with the current statistics of Fermi-LAT are predicted to be comparable to those obtained from other techniques able to explore the unresolved components of the gamma-ray background. The enhanced capabilities of SKA Phase 2, combined with a future generation gamma-ray telescope with improved specifications, can allow us to investigate the whole mass window for weakly interacting massive particles up to the TeV scale.

Cosmology with Phase 1 of the Square Kilometre Array Red Book 2018: Technical specifications and performance forecasts

Abstract We present a detailed overview of the cosmological surveys that we aim to carry out with Phase 1 of the Square Kilometre Array (SKA1) and the science that they will enable. We highlight three main surveys: a medium-deep continuum weak lensing and low-redshift spectroscopic HI galaxy survey over 5 000 deg2; a wide and deep continuum galaxy and HI intensity mapping (IM) survey over 20 000 deg2 from $z = 0.35$ to 3; and a deep, high-redshift HI IM survey over 100 deg2 from $z = 3$ to 6. Taken together, these surveys will achieve an array of important scientific goals: measuring the equation of state of dark energy out to $z \sim 3$ with percent-level precision measurements of the cosmic expansion rate; constraining possible deviations from General Relativity on cosmological scales by measuring the growth rate of structure through multiple independent methods; mapping the structure of the Universe on the largest accessible scales, thus constraining fundamental properties such as isotropy, homogeneity, and non-Gaussianity; and measuring the HI density and bias out to $z = 6$ . These surveys will also provide highly complementary clustering and weak lensing measurements that have independent systematic uncertainties to those of optical and near-infrared (NIR) surveys like Euclid, LSST, and WFIRST leading to a multitude of synergies that can improve constraints significantly beyond what optical or radio surveys can achieve on their own. This document, the 2018 Red Book, provides reference technical specifications, cosmological parameter forecasts, and an overview of relevant systematic effects for the three key surveys and will be regularly updated by the Cosmology Science Working Group in the run up to start of operations and the Key Science Programme of SKA1.

Forecasts of cosmological constraints from HI intensity mapping with FAST, BINGO and SKA-I

We forecast the cosmological constraints of the neutral hydrogen (Hi) intensity mapping (IM) technique with radio telescopes by assuming 1-year of observational time. The current and future radio telescopes that we consider here are Five-hundred-meter Aperture Spherical radio Telescope (FAST), Baryon acoustic oscillations In Neutral Gas Observations (BINGO), and Square Kilometre Array phase I (SKA-I) single-dish experiments. We also forecast the combined constraints of the three radio telescopes with Planck. We find that the 1σ errors of (w0, wa) for BINGO, FAST and SKA-I with respect to the fiducial values are respectively, (0.9293, 3.5792), (0.4083, 1.5878) and (0.3158, 0.4622). This is equivalent to (56.04%, 55.64%) and (66.02%, 87.09%) improvements in constraining (w0, wa) for FAST and SKA-I respectively relative to BINGO. Simulations further show that SKA-I will put more stringent constraints than both FAST and BINGO when each of the experiments is combined with Planck measurements. The 1σ errors for (w0, wa), BINGO + Planck, FAST + Planck and SKA-I + Planck covariance matrices are respectively (0.0832, 0.3520), (0.0791, 0.3313) and (0.0678, 0.2679) implying there is an improvement in (w0, wa) constraints of (4.93%, 5.88%) for FAST + Planck relative to BINGO + Planck and an improvement of (18.51%, 23.89%) in constraining (w0, wa) for SKA-I + Planck relative to BINGO + Planck. We also compared the performance of Planck data plus each single-dish experiment relative to Planck alone, and find that the reduction in (w0, wa) 1σ errors for each experiment plus Planck, respectively, imply the (w0, wa) constraints improvement of (22.96%, 8.45%), (26.76%, 13.84%) and (37.22%, 30.33%) for BINGO + Planck, FAST + Planck and SKA-I + Planck relative to Planck alone. For the nine cosmological parameters in consideration, we find that there is a trade-off between SKA-I and FAST in constraining cosmological parameters, with each experiment being more superior in constraining a particular set of parameters.

Constraints on the growth rate using the observed galaxy power spectrum

The large-scale structure growth index γ provides a consistency test of the standard cosmology and is a potential indicator of modified gravity. We investigate the constraints on γ from next-generation spectroscopic surveys, using the power spectrum that is observed in redshift space, i.e., the angular power spectrum. The angular power spectrum avoids the need for an Alcock-Packzynski correction. It also naturally incorporates cosmic evolution and wide-angle effects, without any approximation. We include the cross-correlations between redshift bins, using a hybrid approximation when the total number of bins is computationally unfeasible. We show that the signal-to-noise on γ increases as the redshift bin-width is decreased. Shot noise per bin also increases—but this is compensated by the increased number of auto- and cross-spectra. In our forecasts, we marginalise over the amplitude of primordial fluctuations and other standard cosmological parameters, including the dark energy equation of state parameter, as well as the clustering bias. Neglecting cross-bin correlations increases the errors by ∼40–150%. Using only linear scales, we find that a DESI-like BGS survey and an HI intensity mapping survey with the SKA1 precursor MeerKAT deliver similar errors of ∼4–6%, while a Euclid-like survey and an SKA1 intensity mapping survey give ∼3% errors.

A first quantification of the effects of absorption for H I intensity mapping experiments

Context. HI intensity mapping (IM) will be used to do precision cosmology, using many existing and upcoming radio observatories. It will measure the integrated HI 21 cm emission signal from “voxels” of the sky at different redshifts. The signal will be contaminated due to absorption, the largest component of which will be the flux absorbed by the HI emitting sources themselves from the potentially bright flux incident on them from background radio continuum sources. Aims. We, for the first time, provide a quantitative estimate of the magnitude of the absorbed flux compared to the emitted HI flux. The ratio of the two fluxes was calculated for various voxels placed at redshifts between 0.1 and 2.5. Methods. We used a cosmological sky simulation of the atomic HI emission line, and summed over the emitted and absorbed fluxes for all sources within voxels at different redshifts. In order to determine the absorbed flux, for each HI source the flux incident from background radio continuum sources was estimated by determining the numbers, sizes, and redshift distribution of radio continuum sources that lie behind it, based on existing observations and simulations. The amount of this incident flux that is absorbed by each HI source was calculated using a relation between integrated optical depth with HI column density determined using observations of damped Lyman-α systems (DLAs) and sub-DLAs. Results. We find that for the same co-moving volume of sky, the HI emission decreases quickly with increasing redshift, while the absorption varies much less with redshift and follows the redshift distribution of faint sources that dominate the number counts of radio continuum sources. This results in the fraction of absorption compared to emission to be negligible in the nearby Universe (up to a redshift of ∼0.5), increases to about 10% at a redshift of one, and continues to increase to about 30% up to a redshift of 2.5. These numbers can vary significantly due to the uncertainty on the exact form of the following relations: firstly, the number counts of radio continuum sources at sub-mJy flux densities; secondly, the relation between integrated optical depth and HI column density of HI sources; and thirdly, the redshift distribution of radio continuum sources up to the highest redshifts. Conclusions. Absorption of the flux incident from background radio continuum sources might become an important contaminant to HI IM signals beyond redshifts of 0.5. The impact of absorption needs to be quantified more accurately using inputs from upcoming deep surveys of radio continuum sources, H I absorption, and HI emission with the Square Kilometre Array and its precursors.

The full-sky angular bispectrum in redshift space

We compute the redshift-dependent angular bispectrum of galaxy number counts at tree-level, including nonlinear clustering bias and estimating numerically for the first time the effect of redshift space distortions (RSD). We show that for narrow redshift bins the amplitude of nonlinear RSD is comparable with the matter density perturbations. While our numerical results only include terms relevant on sub-horizon scales, the formalism can readily be extended to the full tree-level bispectrum. Our approach does not rely on the flat-sky approximation and it can be easily generalized to different sources by including the appropriate bias expansion. We test the accuracy of Limber approximation for different z-bins. We highlight the subtle but relevant differences in the angular bispectrum of galaxy number counts with respect to CMB, due to the different scale dependence of perturbations. Our formalism can also be directly applied to the angular HI intensity mapping bispectrum.

Cosmology in the era of Euclid and the Square Kilometre Array

Theoretical uncertainties on non-linear scales are among the main obstacles to exploit the sensitivity of forthcoming galaxy and hydrogen surveys like Euclid or the Square Kilometre Array (SKA). Here, we devise a new method to model the theoretical error that goes beyond the usual cut-off on small scales. The advantage of this more efficient implementation of the non-linear uncertainties is tested through a Markov-Chain-Monte-Carlo (MCMC) forecast of the sensitivity of Euclid and SKA to the parameters of the standard ΛCDM model, including massive neutrinos with total mass Mν, and to 3 extended scenarios, including 1) additional relativistic degrees of freedom (ΛCDM + Mν + Neff), 2) a deviation from the cosmological constant (ΛCDM + Mν + w0), and 3) a time-varying dark energy equation of state parameter (ΛCDM + Mν + (w0,wa )). We compare the sensitivity of 14 different combinations of cosmological probes and experimental configurations. For Euclid combined with Planck, assuming a plain cosmological constant, our method gives robust predictions for a high sensitivity to the primordial spectral index ns (σ(ns)=0.00085), the Hubble constant H0 (σ(H0)=0.141 km/s/Mpc), the total neutrino mass Mν (σ(Mν)=0.020 eV). Assuming dynamical dark energy we get σ(Mν)=0.030 eV for the mass and (σ(w0), σ(wa)) = (0.0214, 0.071) for the equation of state parameters. The predicted sensitivity to Mν is mostly stable against the extensions of the cosmological model considered here. Interestingly, a significant improvement of the constraints on the extended model parameters is also obtained when combining Euclid with a low redshift HI intensity mapping survey by SKA1, demonstrating the importance of the synergy of Euclid and SKA.

Intensity mapping cross-correlations II: HI halo models including shot noise

HI intensity mapping data traces the large-scale structure matter distribution using the integrated emission of neutral hydrogen gas (HI). The cross-correlation of the intensity maps with optical galaxy surveys can mitigate foreground and systematic effects, but has been shown to significantly depend on galaxy evolution parameters of the HI and the optical sample. Previously, we have shown that the shot noise of the cross-correlation scales with the HI content of the optical samples, such that the shot noise estimation infers the average HI masses of these samples. In this article, we present an adaptive framework for the cross-correlation of HI intensity maps with galaxy samples using our implementation of the halo model formalism (Murray et al 2018, in prep) which utilises the halo occupation distribution of galaxies to predict their power spectra. We compare two HI population models, tracing the spatial halo and the galaxy distribution respectively, and present their auto- and cross-power spectra with an associated galaxy sample. We find that the choice of the HI model and the distribution of the HI within the galaxy sample have minor significance for the shape of the auto- and cross-correlations, but highly impact the measured shot noise amplitude of the estimators, a finding we confirm with simulations. We demonstrate parameter estimation of the HI halo occupation models and advocate this framework for the interpretation of future experimental data, with the prospect of determining the HI masses of optical galaxy samples via the cross-correlation shot noise.

H iintensity mapping for clustering-based redshift estimation

Precision cosmology requires accurate galaxy redshifts, but next generation optical surveys will observe unprecedented numbers of resolved galaxies, placing strain on the amount of spectroscopic follow-up required. We show how useful information can be gained on the redshift distributions of optical galaxy samples from spatial cross-correlations with intensity maps of unresolved HI (21cm) spectral line emission. We construct a redshift distribution estimator, which we test using simulations. We utilise the S3-SAX catalogue which includes HI emission information for each galaxy, which we use to construct HI intensity maps. We also make use of simulated LSST and Euclid-like photometry enabling us to apply the HI clustering calibration to realistic simulated photometric redshifts. While taking into account important limitations to HI intensity mapping such as lost k-modes from foreground cleaning and poor angular resolution due to large receiver beams, we show that excellent constraints on redshift distributions can be provided for an optical photometric sample.

Potential impact of global navigation satellite services on total power H i intensity mapping surveys

Future total-power single-dish HI intensity mapping (HI IM) surveys have the potential to provide unprecedented insight into late time ($z < 1$) cosmology that are competitive with Stage IV dark energy surveys. However, redshifts between $0 < z < 0.2$ lie within the transmission bands of global navigation satellite services (GNSS), and even at higher redshifts out-of-band leakage from GNSS satellites may be problematic. We estimate the impact of GNSS satellites on future single-dish HI IM surveys using realistic estimates of both the total power and spectral structure of GNSS signals convolved with a model SKA beam. Using a simulated SKA HI IM survey covering 30000 sq. deg. of sky and 200 dishes, we compare the integrated GNSS emission on the sky with the expected HI signal. It is found that for frequencies $> 950$ MHz the emission from GNSS satellites will exceed the expected HI signal for all angular scales to which the SKA is sensitive when operating in single-dish mode.

Impact of simulated 1/f noise for HI intensity mapping experiments

Cosmology has entered an era where the experimental limitations are not due to instrumental sensitivity but instead due to inherent systematic uncertainties in the instrumentation and data analysis methods. The field of HI intensity mapping (IM) is still maturing, however early attempts are already systematics limited. One such systematic limitation is 1/f noise, which largely originates within the instrumentation and manifests as multiplicative gain fluctuations. To date there has been little discussion about the possible impact of 1/f noise on upcoming single-dish HI IM experiments such as BINGO, FAST or SKA. Presented in this work are Monte-Carlo end-to-end simulations of a 30 day HI IM survey using the SKA-MID array covering a bandwidth of 950 and 1410 MHz. These simulations extend 1/f noise models to include not just temporal fluctuations but also correlated gain fluctuations across the receiver bandpass. The power spectral density of the spectral gain fluctuations are modelled as a power-law, and characterised by a parameter $\beta$. It is found that the degree of 1/f noise frequency correlation will be critical to the success of HI IM experiments. Small values of $\beta$ ($\beta$ < 0.25) or high correlation is preferred as this is more easily removed using current component separation techniques. The spectral index of temporal fluctuations ($\alpha$) is also found to have a large impact on signal-to-noise. Telescope slew speed has a smaller impact, and a scan speed of 1 deg s$^{-1}$ should be sufficient for a HI IM survey with the SKA.

Constraining the interaction between dark sectors with future HI intensity mapping observations

We study a model of interacting dark matter and dark energy, in which the two components are coupled. We calculate the predictions for the 21-cm intensity mapping power spectra, and forecast the detectability with future single-dish intensity mapping surveys (BINGO, FAST and SKA-I). Since dark energy is turned on at $z\sim 1$, which falls into the sensitivity range of these radio surveys, the HI intensity mapping technique is an efficient tool to constrain the interaction. By comparing with current constraints on dark sector interactions, we find that future radio surveys will produce tight and reliable constraints on the coupling parameters.

Cosmological parameter forecasts for H i intensity mapping experiments using the angular power spectrum

HI intensity mapping is a new observational technique to survey the large-scale structure of matter using the 21 cm emission line of atomic hydrogen (HI). In this work, we simulate BINGO (BAO from Integrated Neutral Gas Observations) and SKA (Square Kilometre Array) phase-1 dish array operating in auto-correlation mode. For the optimal case of BINGO with no foregrounds, the combination of the HI angular power spectra with Planck results allows $w$ to be measured with a precision of $4\%$, while the combination of the BAO acoustic scale with Planck gives a precision of $7\%$. We consider a number of potentially complicating effects, including foregrounds and redshift dependent bias, which increase the uncertainty on $w$ but not dramatically; in all cases the final uncertainty is found to be $\Delta w < 8\%$ for BINGO. For the combination of SKA-MID in auto-correlation mode with Planck, we find that, in ideal conditions, $w$ can be measured with a precision of $4\%$ for the redshift range $0.35 < z < 3$ (i.e., for the bandwidth of $\Delta \nu = [350, 1050]$ MHz) and $2\%$ for $0 < z < 0.49$ (i.e., $\Delta \nu = [950, 1421]$ MHz). Extending the model to include the sum of neutrino masses yields a $95\%$ upper limit of $\sum m_\nu < 0.24$ eV for BINGO and $\sum m_\nu < 0.08$ eV for SKA phase 1, competitive with the current best constraints in the case of BINGO and significantly better than them in the case of SKA.