The slingshot effect as a probe of transverse motions of galaxies
Research output: Contribution to journal › Article › peer-review
Aims - Our aim is to show that the slingshot effect can be measured by stacking the signals of galaxies falling into a collapsing cluster. Furthermore, we evaluate whether the effect can probe modified gravity.
Methods - We used data from a simulated galaxy catalogue (MultiDark Planck 2) to mimic observations. We identified a 1015 M⊙ cluster, and made maps of the slingshot effect for photons passing near 8438 infalling galaxies. To emulate instrument noise, we added uncorrelated Gaussian noise to each map. We assumed that the average velocity is directed towards the centre of the cluster. The maps were rotated according to the expected direction of motion. This assures that the dipole signal adds up constructively when stacking the maps. We compared the stacked maps to a dipole stencil to determine the quality of the signal. We also evaluated the probability of fitting the stencil in the absence of the slingshot signal.
Results - Each galaxy gives a signal of around ΔT/T ≈ 10−9, while the current precision of CMB experiments is ΔT/T ≈ 4 × 10−6. By stacking around 10 000 galaxies and performing a stencil fit, the slingshot signal can be over the detectable threshold with today’s experiments. However, due to the difficulty of distinguishing an actual signal from false positives, future CMB experiments must be used to be certain of the strength of the observed signal.
|Number of pages||12|
|Journal||Astronomy and Astrophysics|
|Early online date||31 Jul 2019|
|Publication status||Published - 1 Aug 2019|
- The slingshot effect
Rights statement: Credit: R. Hagala, C. Llinares & D. F. Mota, A&A, 628, A30, 2019, reproduced with permission, © ESO.
Accepted author manuscript (Post-print), 1.19 MB, PDF document