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Register a new userCosmological parameter forecasts for HI intensity mapping experiments using the angular power spectrum
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Added by
Lucas Collis Olivari
Publication date
2017
fields
Physics
and research's language is
English
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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 $Delta u = [350, 1050]$ MHz) and $2%$ for $0 < z < 0.49$ (i.e., $Delta u = [950, 1421]$ MHz). Extending the model to include the sum of neutrino masses yields a $95%$ upper limit of $sum m_ u < 0.24$ eV for BINGO and $sum m_ u < 0.08$ 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.
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We assess the performance of the multipole expansion formalism in the case of single-dish HI intensity mapping, including instrumental and foreground removal effects. This formalism is used to provide MCMC forecasts for a range of HI and cosmological parameters, including redshift space distortions and the Alcock-Paczynski effect. We first determine the range of validity of our power spectrum modelling by fitting to simulation data, concentrating on the monopole, quadrupole, and hexadecapole contributions. We then show that foreground subtraction effects can lead to severe biases in the determination of cosmological parameters, in particular the parameters relating to the transverse BAO rescaling, the growth rate and the HI bias ($alpha_perp$, $overline{T}_text{HI} fsigma_8$, and $overline{T}_text{HI} b_text{HI} sigma_8$, respectively). We attempt to account for these biases by constructing a 2-parameter foreground modelling prescription, and find that our prescription leads to unbiased parameter estimation at the expense of increasing the estimated uncertainties on cosmological parameters. In addition, we confirm that instrumental and foreground removal effects significantly impact the theoretical covariance matrix, and cause the covariance between different multipoles to become non-negligible. Finally, we show the effect of including higher-order multipoles in our analysis, and how these can be used to investigate the presence of instrumental and systematic effects in HI intensity mapping data.
Intensity mapping (IM) with neutral hydrogen is a promising avenue to probe the large scale structure of the Universe. In this paper, we demonstrate that using the 64-dish MeerKAT radio telescope as a connected interferometer, it is possible to make a statistical detection of HI in the post-reionization Universe. With the MIGHTEE (MeerKAT International GHz Tiered Extragalactic Exploration) survey project observing in the L-band ($856 < u < 1712$ MHz, $z < 0.66$), we can achieve the required sensitivity to measure the HI IM power spectrum on quasi-linear scales, which will provide an important complementarity to the single-dish IM MeerKAT observations. We present a purpose-built simulation pipeline that emulates the MIGHTEE observations and forecast the constraints that can be achieved on the HI power spectrum at $z = 0.27$ for $k > 0.3$ $rm{Mpc}^{-1}$ using the foreground avoidance method. We present the power spectrum estimates with the current simulation on the COSMOS field that includes contributions from HI, noise and point source models constructed from the observed MIGHTEE data. The results from our textit{visibility} based pipeline are in qualitative agreement to the already available MIGHTEE data. This paper demonstrates that MeerKAT can achieve very high sensitivity to detect HI with the full MIGHTEE survey on quasi-linear scales (signal-to-noise ratio $> 7$ at $k=0.49$ $rm{Mpc}^{-1}$) which are instrumental in probing cosmological quantities such as the spectral index of fluctuation, constraints on warm dark matter, the quasi-linear redshift space distortions and the measurement of the HI content of the Universe up to $zsim 0.5$.
The 21-cm line of neutral hydrogen (HI) opens a new avenue in our exploration of the Universes structure and evolution. It provides complementary data with different systematics, which aim to improve our current understanding of the $Lambda$CDM model. Among several radio cosmological surveys designed to measure this line, BINGO is a single dish telescope mainly designed to detect Baryon Acoustic Oscillations (BAO) at low redshifts ($0.127 < z < 0.449$). Our goal is to assess the capabilities of the fiducial BINGO setup to constrain the cosmological parameters and analyse the effect of different instrument configurations. We will use the 21-cm angular power spectra to extract information about the HI signal and the Fisher matrix formalism to study BINGO projected constraining power. We use the Phase 1 fiducial configuration of the BINGO telescope to perform our cosmological forecasts. In addition, we investigate the impact of several instrumental setups and different cosmological models. Combining BINGO with Planck temperature and polarization data, we project a $1%$ and a $3%$ precision measurement at $68%$ CL for the Hubble constant and the dark energy (DE) equation of state (EoS), respectively, within the wCDM model. Assuming a CPL parametrization, the EoS parameters have standard deviations given by $sigma_{w_0} = 0.30$ and $sigma_{w_a} = 1.2$. We find that BINGO can also help breaking degeneracies in alternative models, which improves the cosmological constraints significantly. Moreover, we can access information about the HI density and bias, obtaining $sim 8.5%$ and $sim 6%$ precision, respectively, assuming they vary with redshift at three independent bins. The fiducial BINGO configuration will be able to extract significant information from the HI distribution and provide constraints competitive with current and future cosmological surveys. (Abridged)
We forecast ability of dedicated 21 cm intensity mapping experiments to constraint primordial non-Gaussianity using power spectrum and bispectrum. We model the signal including the non-linear biasing expansion using a generalized halo model approach. We consider the importance of foreground filtering scale and of the foreground wedge. We find that the current generation intensity mapping experiments like CHIME do not posses sufficient sensitivity to be competitive with the existing limits. On the other hand, upcoming experiments like HIRAX can improve the current constraints and the proposed PUMA experiment can substantially improve them, reaching sensitivities below $sigma (f_{rm NL})<5$ for equilateral and orthogonal configurations and $sigma( f_{rm NL}) < 1$ for the local shape if good foreground control is achieved.
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 $zsim3$ serving as our primary case study, we expect a $sim10%$ attenuation of the spherically averaged power spectrum on average at relevant scales of $kapprox0.2$-$0.3$ Mpc$^{-1}$, compared to $sim25%$ for the interferometric Millimetre-wave Intensity Mapping Experiment (mmIME) targeting shot noise from CO lines at $zsim1$-$5$ at scales of $kgtrsim1$ Mpc$^{-1}$. 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.
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