Painting a full radio sky -- Empirical mock catalogues with multiple source populations for future radio surveys

Abstract

Upcoming radio surveys will probe the sky with unprecedented depth and sky coverage, enabling a broad range of cosmological and astrophysical applications, as well as powerful synergies with experiments at other wavelengths. The preparation and scientific exploitation of these surveys require realistic mock catalogues that capture the complexity of the radio sky and the interplay of its emitting components. We present a modular and extensible algorithm for generating empirical simulations over the full radio sky, i.e. a solid angle of $4π$ steradians ($f_{\rm sky}=1$), down to redshift $z=5$, comprising both radio continuum and line emission. The framework combines a simulated dark-matter light-cone with empirically sampled galaxy populations and a probabilistic galaxy-halo assignment scheme, producing self-consistent mock catalogues including multiple radio populations on the same light-cone. We release two public catalogues: a shallow catalogue, fully constrained by existing observational data and limited to flux thresholds of $S_\text{1.4 GHz}^\text{lim} \sim 8\times10^{-5}\ \text{Jy}$ at $1.4\ \text{GHz}$ and $S_\text{21}^\text{lim} \sim 2\ \text{Jy}\cdot\text{Hz}$ for the HI 21 cm line; and a deep catalogue extending the calibrated empirical model to better sensitivities, broadly matching future SKAO surveys, with flux limits of $S_\text{1.4 GHz}^\text{lim} \sim 4\times10^{-5}\ \text{Jy}$ and $S_\text{21}^\text{lim} \sim 0.3\ \text{Jy}\cdot\text{Hz}$. The catalogues include radio continuum active galactic nuclei and star-forming galaxies, together with HI-emitting galaxies, for a total of more than 260 million sources in the shallow catalogue and more than 1 billion in the deep catalogue. We validate the simulations by analysing their statistical properties: the mocks reproduce the targeted clustering and population statistics while retaining minimal physical assumptions.

Figures (17)

• Figure 1: Average halo occupation distribution with the parameterisation defined in Eq.s \ref{['eq:hod_cen']} and \ref{['eq:hod_sat']} and parameter values: $M_\text{min}=10^{10}~M_\odot h^{-1}$, $\sigma_{\log M} = 1$, $M_1 = 10^{10}~M_\odot h^{-1}$, $M_\text{cut}=10^{12}~M_\odot h^{-1}$ and $\alpha = 1$. The blue and green solid lines mark the contributes from central and satellite galaxies, respectively, while the dashed black line is the sum of the two. The dotted gray line highlights the threshold above which at least 1 galaxy is hosted, on average, by an halo of a given mass $M_h$.
• Figure 2: Left: Projection of the whole light-cone in the redshift range $0 < z \leq 0.5$, the colour-scale shows the distribution of HI galaxies from lighter (lower number density) to darker (higher number density). Right: FoV $= 12\ \deg$ zoom-in of the region marked by the black circle in the left-side projection showing the positions of AGNs (red markers) and SFGs (orange markers) distributed on top of the HIGs.
• Figure 3: Average halo occupation distribution (HOD) separated between centrals (left panel) and satellites (right panel) as a function of the halo mass for CoG in the catalogues. The black solid line marks the distribution of sub-haloes within haloes in the original DM-only catalogue. The gray dashed and dotted lines mark the best-fitting HOD models obtained for the shallow and deep catalogue, respectively. Light orange circles and dark orange crosses mark the distribution of mock CoG in the final shallow and deep catalogue, respectively.
• Figure 4: Same as Fig. \ref{['fig:CoG_NcNs']} but for HIG. The measurement on the shallow and deep catalogue are marked by light blue circles and dark blue crosses, respectively.
• Figure 5: Redshift distribution of the CoG population in both the shallow simulation (left panel) and the deep simulation (right panel). Th normalized redshift distribution, $\mathcal{N}(z)$ of the whole population (orange) is divided into AGNs (hatched red) and SFGs (hatched yellow). The measurements on the simulated light-cones are compared against the prediction of the fitted halo model (dashed gray line).