Dark Matter Substructure Detection Using Spatially Resolved Spectroscopy of Lensed Dusty Galaxies

Abstract

We investigate how strong lensing of dusty, star-forming galaxies by foreground galaxies can be used as a probe of dark matter halo substructure. We find that spatially resolved spectroscopy of lensed sources allows dramatic improvements to measurements of lens parameters. In particular we find that modeling of the full, three-dimensional (angular position and radial velocity) data can significantly facilitate substructure detection, increasing the sensitivity of observables to lower mass subhalos. We carry out simulations of lensed dusty sources observed by early ALMA (Cycle 1) and use a Fisher matrix analysis to study the parameter degeneracies and mass detection limits of this method. We find that, even with conservative assumptions, it is possible to detect galactic dark matter subhalos of ∼ 10 8 M with high significance in most lensed DSFGs. Specifically, we find that in typical DSFG lenses, there is a ∼ 55% probability of detecting a substructure with M > 10 8 M with more than 5σ detection significance in each lens, if the abundance of substructure is consistent with previous lensing results. The full ALMA array, with its significantly enhanced sensitivity and resolution, should improve these estimates considerably. Given the sample of ∼ 100 lenses provided by surveys like the South Pole Telescope, our understanding of dark matter substructure in typical galaxy halos is poised to improve dramatically over the next few years.

Source-position transformation: an approximate invariance in strong gravitational lensing

“…0. 001) with ALMA (Hezaveh et al 2013), the Extremely Large Telescope (ELT), or the James Webb Space Telescope (JWST). It still has to be investigated how critical the SPT could be for sources observed at those resolutions if substructures are not explicitly included in the lens models and/or if reasonable freedom is allowed regarding the angular structure of the lens (e.g.…”

How well can cold dark matter substructures account for the observed radio flux-ratio anomalies

“…The resulting CDM substructure fraction is in consistent with the ones derived from N-body simulations (see Section 3.2.2). More highresolution images of lensed dusty star-forming galaxies will also soon be available from the Atacama Large Millimeter/submillimeter Array (ALMA), which can also be used to constrain CDM substructures via the induced image distortion (Hezaveh et al 2013). Xu et al (2012) investigated the effects from CDM haloes along the line of sight to a lensed quasar.…”

Simulating nonlinear cosmological structure formation with massive neutrinos

“…However, it is not yet clear if this method is accurate inside collapsed and virialized regions such as halos or subhalos, whose abundance will likely provide stringent constraints on WDM models in upcoming years (e.g. Hezaveh et al 2013Hezaveh et al , 2016. Alternatively, Hobbs et al (2016) have proposed that adaptive softening of the gravitational force can help to suppress spurious structure found in cold start simulations of WDM cosmologies.…”