Probing cold dark matter subhaloes with simulated ALMA observations of macrolensed sub-mm galaxies

Abstract

If the dark matter halos of galaxies contain large numbers of subhalos as predicted by the ΛCDM model, these subhalos are expected to appear in strong galaxy-galaxy lens systems as small-scale perturbations in individual images. We simulate observations of multiply-lensed sub-mm galaxies at z ∼ 2 as a probe of the dark matter halo of a lens galaxy at z ∼ 0.5. We present detection limits for dark substructures based on a visibility plane analysis of simulated Atacama Large Millimeter/submillimeter Array (ALMA) data in bands 7, 8 and 9. We explore two effects: local surface brightness anomalies on angular scales similar to the Einstein radius and the astrometric shift of macroimages. This improves the sensitivity of our lens modeling to the mass of the lens perturber. We investigate the sensitivity of the detection of low-mass subhalos to the projected position of the subhalo on the image plane as well as the source structure and inner density profile of the lens. We demonstrate that, using the most extended ALMA configuration, pseudo-Jaffe subhalos can be detected with 99% confidence down to M = 10 7 M . We show how the detection threshold for the three ALMA bands depends on the projected position of the subhalo with respect to the lensed images and conclude that, despite the highest nominal angular resolution, band 9 provides the poorest sensitivity due to observational noise. All simulations use the ALMA Full ops most extended ALMA configuration setup in casa. -sized CDM halos are best-fit by a mass function of the type:

Highly Magnified Stars in Lensing Clusters: New Evidence in a Galaxy Lensed by MACS J0416.1-2403

“…An alternative approach is to use the flux data for the whole arc and statistically test the symmetry of the two-dimensional surface brightness pattern, to check if asymmetry increases close to the critical curve. This idea is along the lines of detecting substructure in galaxy lenses from residuals in fitting a smooth lens model to the observed surface brightness pattern (Hezaveh et al 2013;Asadi et al 2017;Birrer et al 2017). In the subsections below we describe our method, and demonstrate how it provides additional evidence for flux asymmetry.…”

Probing the nature of dark matter particles with stellar streams

“…On these scales, such substructures would be completely dark matter dominated, and contain too few stars to be observed directly. A number of strategies have been proposed to indirectly probe low mass dark matter halos, including analyses of the impact on Lyα forest observations [14][15][16][17][18][19][20] and perturbations of strong gravitational lenses [21][22][23][24][25][26][27][28][29].…”

Axions: From Magnetars and Neutron Star Mergers to Beam Dumps and BECs

“…The work in [457][458][459] shows that for m = 10 −22 eV, the halo mass function is affected at scale as large as 10 10 M , and sharply cut off at 10 7 − 10 8 M . Probes of structure suppression at this scale include Lyman-α (excluding 10 −22 eV m 2.3 × 10 −21 eV) [426,[460][461][462][463][464], halo mass function from stellar stream [465,466] and strong lensing [466][467][468][469][470][471][472][473][474][475][476] (m 2.1 × 10 −21 eV), from Milky Way satellite counting [477][478][479][480][481][482], and galaxy UV luminosity function [483][484][485][486][487]. Alternatively, if one takes the empirical soliton-halo relation from simulation [420,447], the soliton-halo profile can be constrained by rotation curve data [419,440] and stellar orbits around Sgr A* (to exclude 2 × 10 −20 eV m 8 × 10 −19 eV) and M87* (to exclude m 4 × 10 −22 eV) [488].…”