Secondary halo bias in line-intensity mapping
Rui Lan Jun
Line-intensity mapping (LIM) promises to map larger cosmic volumes more cheaply, whilst also providing additional insights on all scales by detecting the contribution from faint galaxies undetected in traditional galaxy surveys. In LIM, galaxies are weighted by their emission line luminosities, which are strongly correlated with the star formation rate (SFR) for many emission lines. As a result, baryonic physics influences the measured power spectrum, affecting inferences about the underlying matter distribution. Models often assume that the SFR of a galaxy can be predicted by its halo mass. We use the IllustrisTNG simulations to test this assumption, finding that using halo mass alone leads to systematic errors of around 5% in the LIM power spectrum on scales of 10s of Mpc. We show that this bias is partially due to the secondary dependence of SFR on concentration at fixed mass for lower mass halos, and on the contribution of satellites to the SFR for higher mass halos. Our results show the need for more comprehensive models of the galaxy-halo connection in order to exploit the potential of LIM for constraining cosmological parameters.
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