[Paper Review] MeerKLASS: MeerKAT Large Area Synoptic Survey

Mário G. Santos, M. E. Cluver+36 more|arXiv (Cornell University)|Sep 18, 2017

Spectroscopy and Chemometric AnalysesChemistry66 citations

TL;DR

MeerKLASS proposes a wide-area MeerKAT survey (~4000 deg2 over ~4000 hours) to pioneer HI intensity mapping and continuum galaxy studies, enabling early BAO/RSD detection, multi-tracer PNG constraints, and transformational multi-wavelength insights ahead of SKA1-MID.

ABSTRACT

We discuss the ground-breaking science that will be possible with a wide area survey, using the MeerKAT telescope, known as MeerKLASS (MeerKAT Large Area Synoptic Survey). The current specifications of MeerKAT make it a great fit for science applications that require large survey speeds but not necessarily high angular resolutions. In particular, for cosmology, a large survey over $\sim 4,000 \, { m deg}^2$ for $\sim 4,000$ hours will potentially provide the first ever measurements of the baryon acoustic oscillations using the 21cm intensity mapping technique, with enough accuracy to impose constraints on the nature of dark energy. The combination with multi-wavelength data will give unique additional information, such as exquisite constraints on primordial non-Gaussianity using the multi-tracer technique, as well as a better handle on foregrounds and systematics. Such a wide survey with MeerKAT is also a great match for HI galaxy studies, providing unrivalled statistics in the pre-SKA era for galaxies resolved in the HI emission line beyond local structures at z > 0.01. It will also produce a large continuum galaxy sample down to a depth of about 5\,$μ$Jy in L-band, which is quite unique over such large areas and will allow studies of the large-scale structure of the Universe out to high redshifts, complementing the galaxy HI survey to form a transformational multi-wavelength approach to study galaxy dynamics and evolution. Finally, the same survey will supply unique information for a range of other science applications, including a large statistical investigation of galaxy clusters as well as produce a rotation measure map across a huge swathe of the sky. The MeerKLASS survey will be a crucial step on the road to using SKA1-MID for cosmological applications and other commensal surveys, as described in the top priority SKA key science projects (abridged).

Motivation & Objective

• Motivate a wide-area MeerKAT survey to enable pioneering cosmology and galaxy evolution studies.
• Forecast the capability to detect HI 21cm intensity mapping signals, BAO, and RSDs.
• Assess multi-tracer constraints on primordial non-Gaussianity and cross-correlations with CMB.
• Demonstrate the continuum survey’s potential to constrain dark energy with high redshift radio galaxies.
• Explore HI galaxy evolution, clusters, and AGN demographics through a large, multi-wavelength capable survey.

Proposed method

• Adopt single-dish auto-correlation and interferometric data from MeerKAT for a ~4000 hr, ~4000 deg2 survey.
• Model HI intensity mapping signal with a prescribed M_HI(M) halo model to derive the HI brightness temperature, bias, and Omega_HI evolution.
• Forecast HI power spectrum P^HI(z,k,μ) including redshift-space distortions and use Fisher analysis to estimate constraints on Omega_HI b_HI.
• Evaluate cross-correlation opportunities with optical surveys (DES, BOSS DR12-like) to reduce systematics and improve parameter constraints.
• Forecast continuum radio galaxy counts and redshift distribution under flux cuts to assess dark energy constraints via angular power spectra and multi-bin tomography.
• Discuss multi-tracer techniques combining MeerKAT with DES to improve PNG (f_NL) constraints beyond Planck.
• Explore cross-correlations with CMB lensing and other higher-order statistics for additional cosmological information.

Experimental results

Research questions

• RQ1 Can HI intensity mapping with MeerKLASS detect BAO and RSD signals, and with what precision across L-band and UHF-band?
• RQ2 How well can multi-tracer approaches with MeerKLASS and DES constrain primordial non-Gaussianity (f_NL) relative to Planck?
• RQ3 What constraints on the HI density parameter Omega_HI and HI bias b_HI can MeerKLASS achieve across redshift bins?
• RQ4 What dark energy constraints (w0, wa) can be achieved from the continuum survey through angular power spectra and redshift binning?
• RQ5 What additional insights into galaxy evolution, AGN, and clusters can be gained from the wide-area, multi-wavelength MeerKLASS data?

Key findings

• Forecasted fractional uncertainties on Omega_HI b_HI are provided for L-band and UHF-band across redshift bins, e.g., at z=0.1 (0.010 for L-band) and z=1.4 (0.042 for UHF-band).
• Cross-correlation with optical surveys (DES, BOSS-like) can yield competitive constraints on HI-related quantities and improve robustness against systematics.
• MeerKLASS envisages potential first detections of BAO and RSD via HI intensity mapping, with significant S/N improvements in L-band for BAO observables and growth rate fσ8.
• Multi-tracer approaches using MeerKAT and DES can yield f_NL constraints better than Planck in optimistic overlap scenarios.
• Continuum observations could detect ~10 million radio galaxies, enabling precise dark energy constraints via angular power spectra with redshift binning up to z>2.5.
• The survey will also enable studies of HI in resolved galaxies, galaxy clusters, high-z AGN, and RM maps, forming a transformational multi-wavelength dataset.