Cosmological Prediction from the joint observation of MeerKAT and CSST at $z$ = 0.4 $\sim$ 1.2

TL;DR

This work forecasts cosmological constraints from the joint observation of MeerKAT HI intensity mapping and CSST spectroscopic galaxies across $z\approx0.4$–$1.2$ by simulating realistic data with the Jiutian-1G box. It develops an end-to-end pipeline that includes HI mass modeling, instrument effects (beam patterns and polarization leakage), Galactic and extragalactic foregrounds, and PCA/SVD-based foreground removal, followed by transfer-function–based signal compensation. By fitting the cross-power spectrum $P_{\rm HI,g}(k)$ together with the galaxy auto-spectrum, the study constrains the products $\Omega_{\rm HI} b_{\rm HI} b_g r_{\rm HI,g}$ and $\Omega_{\rm HI} b_{\rm HI} r_{\rm HI,g}$ with about $6$–$8\%$ relative accuracy in three redshift bins, a factor of 3–4 improvement over current MeerKAT results. The results demonstrate that a large overlapping MeerKAT-CSST survey can robustly probe the co-evolution of HI and galaxies and the evolution of large-scale structure, providing a practical framework for forthcoming data analyses.

Abstract

Cross-correlating neutral hydrogen (HI) 21cm intensity mapping with galaxy surveys provides an effective probe of astrophysical and cosmological information. This work presents a cross-correlation analysis between MeerKAT single-dish HI intensity mapping and Chinese Space Station Survey Telescope (CSST) spectroscopic galaxy surveys in $z=0.4\sim1.2$, which will share a survey area of several thousand square degrees. Utilizing Jiutian-1G cosmological simulation, we simulate the observational data of MeerKAT and CSST with survey areas from $\sim1600$ to $600$ deg$^2$ at $z=0.5$, 0.7, and 1. The effects of beam pattern, polarization leakage, and different foregrounds in the MeerKAT HI intensity mapping are considered in the simulation. After employing foreground removal with the principal component analysis (PCA) method and performing signal compensation, we derive the cross-power spectra of MeerKAT and CSST. We perform the joint constraint using the CSST galaxy auto-power spectra and MeerKAT-CSST cross-power spectra with the least-squares fitting method. The constraint results show that, in the simulated survey area, the relative accuracy can achieve $6\%\sim 8\%$ for the parameter products $Ω_{\rm HI}b_{\rm HI}b_{g}r_{\mathrm{HI},g}$ and $Ω_{\rm HI}b_{\rm HI}r_{\mathrm{HI},g}$ at the three redshifts, which is $3\sim4$ times smaller than the current result. These findings indicate that the full MeerKAT-CSST joint observation with thousands of square degrees overlapping survey area can be a powerful probe of large-scale structure, and has the ability to provide information on cosmic evolution of HI and galaxies in a wide redshift range.

Figures (13)

• Figure 1: The survey trails in the middle day of the MeerKAT observational plan. The blue, orange, green, and red lines are the azimuth angles at $21^{\circ}$, $43^{\circ}$, $62^{\circ}$, and $80^{\circ}$, respectively. The blue, orange, and red dashed lines denote the sky area which the box size of Jiutian-1G corresponds to at $z=0.5$, $z=0.7$ and $z=1$, respectively.
• Figure 2: The patterns of the MeerKAT primary beam model at 930 MHz obtained using the EIDOS package. The upper row are the beam patterns of I and polarization Q and U. The lower row are the beam patterns of polarization leakage from Q and U to I.
• Figure 3: The simulated HI signal map in MeerKAT intensity mapping for the central frequency slice of each simulation box at z=0.5, 0.7, and 1.
• Figure 4: The brightness temperature maps of the Galactic emission at 930 MHz. The upper row are the maps of I and polarization Q and U. The lower row are the maps of polarization leakage from Q and U to I.
• Figure 5: The brightness temperature maps of the extragalactic point sources at 930 MHz. The first row are total intensity maps of point sources, the left panel is the non-masking map and the right panel is the map masked point sources $>10$ mJy. The second row are the polarization Q and U of non-masking point sources map and the third row are the corresponding polarization leakage maps from Q, U to I.