Separate Universe simulations with IllustrisTNG: baryonic effects on power spectrum responses and higherorder statistics
Abstract
We measure power spectrum response functions in the presence of baryonic physical processes using separate universe simulations with the IllustrisTNG galaxy formation model. The response functions describe how the smallscale power spectrum reacts to longwavelength perturbations and they can be efficiently measured with the separate universe technique by absorbing the effects of the long modes into a modified cosmology. Specifically, we focus on the total firstorder matter power spectrum response to an isotropic density fluctuation R_{1}(k, z), which is fully determined by the logarithmic derivative of the nonlinear matter power spectrum dlnP_{m}(k, z)/dlnk and the growthonly response function G_{1}(k, z). We find that G_{1}(k, z) is not affected by the baryonic physical processes in the simulations at redshifts z < 3 and on all scales probed (k ≲ 15 h Mpc^{1}; i.e. length scales ≳ 0.4 Mpc h^{1}). In practice, this implies that the power spectrum fully specifies the baryonic dependence of its response function. Assuming an idealized lensing survey setup, we evaluate numerically the baryonic impact on the squeezedlensing bispectrum and the lensing supersample power spectrum covariance, which are given in terms of responses. Our results show that these higherorder lensing statistics can display varying levels of sensitivity to baryonic effects compared to the power spectrum, with the squeezed bispectrum being the least sensitive. We also show that ignoring baryonic effects on lensing covariances slightly overestimates the error budget (and is therefore conservative from the point of view of parameter error bars) and likely has negligible impact on parameter biases in inference analyses.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 September 2019
 DOI:
 10.1093/mnras/stz1807
 arXiv:
 arXiv:1904.02070
 Bibcode:
 2019MNRAS.488.2079B
 Keywords:

 gravitational lensing: weak;
 largescale structure of Universe;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 15 pages, 6 figures, 1 table