Power spectrum of dark matter substructure in strong gravitational lenses
Abstract
Studying the smallest selfbound dark matter structure in our Universe can yield important clues about the fundamental particle nature of dark matter. Galaxyscale strong gravitational lensing provides a unique way to detect and characterize dark matter substructures at cosmological distances from the Milky Way. Within the cold dark matter (CDM) paradigm, the number of lowmass subhalos within lens galaxies is expected to be large, implying that their contribution to the lensing convergence field is approximately Gaussian and could thus be described by their power spectrum. We develop here a general formalism to compute from first principles the substructure convergence power spectrum for different populations of dark matter subhalos. As an example, we apply our framework to two distinct subhalo populations: a truncated NavarroFrenkWhite subhalo population motivated by standard CDM, and a truncated cored subhalo population motivated by selfinteracting dark matter (SIDM). We study in detail how the subhalo abundance, mass function, internal density profile, and concentration affect the amplitude and shape of the substructure power spectrum. We determine that the power spectrum is mostly sensitive to a specific combination of the subhalo abundance and moments of the mass function, as well as to the average tidal truncation scale of the largest subhalos included in the analysis. Interestingly, we show that the asymptotic slope of the substructure power spectrum at large wave number reflects the internal density profile of the subhalos. In particular, the SIDM power spectrum exhibits a characteristic steepening at large wave number absent in the CDM power spectrum, opening the possibility of using this observable, if at all measurable, to discern between these two scenarios.
 Publication:

Physical Review D
 Pub Date:
 January 2018
 DOI:
 10.1103/PhysRevD.97.023001
 arXiv:
 arXiv:1707.04590
 Bibcode:
 2018PhRvD..97b3001D
 Keywords:

 Astrophysics  Cosmology and Nongalactic Astrophysics;
 High Energy Physics  Phenomenology
 EPrint:
 15 pages + appendices, 7 figures