Measuring the tidal response of structure formation: anisotropic separate universe simulations using TREEPM
Abstract
We present anisotropic 'separate universe' simulations that modify the N-body code GADGET4 in order to represent a large-scale tidal field through an anisotropic expansion factor. These simulations are used to measure the linear, quasi-linear, and non-linear response of the matter power spectrum to a spatially uniform trace-free tidal field up to wavenumber $k = {7\, h\, {\rm Mpc}^{-1}}$ . Together with the response to a large-scale overdensity measured in previous work, this completely describes the non-linear matter bispectrum in the squeezed limit. We find that the response amplitude does not approach zero on small scales in physical coordinates, but rather a constant value at z = 0, RK ≈ 0.5 for $k \ge 3\, h\, {\rm Mpc}^{-1}$ up to the scale where we consider our simulations reliable, $k \le 7\, h\, {\rm Mpc}^{-1}$ . This shows that even the inner regions of haloes are affected by the large-scale tidal field. We also measure directly the alignment of halo shapes with the tidal field, finding a clear signal that increases with halo mass.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- May 2021
- DOI:
- 10.1093/mnras/stab473
- arXiv:
- arXiv:2003.06427
- Bibcode:
- 2021MNRAS.503.1473S
- Keywords:
-
- methods: numerical;
- large-scale structure of Universe;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 19 pages, 9 figures