Abstract
Inspired by the recent detection of the 21-cm absorption signal from primordial neutral hydrogen at z~17 by EDGES, a class of dark matter (DM) models with non-gravitational baryon-DM scattering (BDMS) becomes more appealing. The intergalactic medium (IGM) can be cooler in these BDMS models compared with the case of the standard cold DM, producing deep absorption depths as measured by EDGES. The effect of BDMS previously has only been studied in the linear regime for the IGM, and the constraints on parameters are incomplete, leaving a open region in the phenomenological parameter space consistent with the EDGES signal. We investigate the effect of BDMS in the non-linear regime of early structure formation to place new constraints on BDMS. We find that BDMS can significantly affect the abundance of star-forming minihaloes, and a large region in the parameter space is ruled out, in which star formation is significantly suppressed at zgtrsim 20, inconsistent with the timing of the EDGES signal. Our work is exploratory (semi-analytical) and far from a full answer. However, with future detailed cosmological simulations and improved 21-cm observations, more insights into the particle-physics nature of DM will be obtained from the perspective of early structure formation.
If you would like to know more details of this work, please read our paper: https://arxiv.org/abs/1902.09650