Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher.
Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?
Some links on this page may take you to nonfederal websites. Their policies may differ from this site.

Time delay cosmography uses the arrival time delays between images in strong gravitational lenses to measure cosmological parameters, in particular the Hubble constant H0. The lens models used in time delay cosmography omit dark matter subhalos and lineofsight halos because their effects are assumed to be negligible. We explicitly quantify this assumption by analyzing realistic mock lens systems that include full populations of dark matter subhalos and lineofsight halos, applying the same modeling assumptions used in the literature to infer H0. We base the mock lenses on six quadruplyimaged quasars that have delivered measurements of the Hubble constant, and quantify the additional uncertainties and/or bias on a lensbylens basis. We show that omitting dark substructure does not bias inferences of H0. However, perturbations from substructure contribute an additional source of random uncertainty in the inferred value of H0 that scales as the square root of the lensing volume divided by the longest time delay. This additional source of uncertainty, for which we provide a fitting function, ranges from 0.6−2.4%. It may need to be incorporated in the error budget as the precision of cosmographic inferences from single lenses improves, and sets a precision limit on inferences from single lenses.

ABSTRACT The primordial matter power spectrum quantifies fluctuations in the distribution of dark matter immediately following inflation. Over cosmic time, overdense regions of the primordial density field grow and collapse into dark matter haloes, whose abundance and density profiles retain memory of the initial conditions. By analysing the image magnifications in 11 strongly lensed and quadruply imaged quasars, we infer the abundance and concentrations of lowmass haloes, and cast the measurement in terms of the amplitude of the primordial matter power spectrum. We anchor the power spectrum on large scales, isolating the effect of smallscale deviations from the Lambda cold dark matter (ΛCDM) prediction. Assuming an analytic model for the power spectrum and accounting for several sources of potential systematic uncertainty, including three different models for the halo mass function, we obtain correlated inferences of $\log _{10}\left(P / P_{\Lambda \rm {CDM}}\right)$, the power spectrum amplitude relative to the predictions of the concordance cosmological model, of $0.0_{0.4}^{+0.5}$, $0.1_{0.6}^{+0.7}$, and $0.2_{0.9}^{+1.0}$ at k = 10, 25, and 50 $\rm {Mpc^{1}}$ at $68 {{\ \rm per\ cent}}$ confidence, consistent with CDM and singlefield slowroll inflation.

Abstract The massconcentration relation of dark matter halos reflects the assembly history of objects in hierarchical structure formation scenarios, and depends on fundamental quantities in cosmology such as the slope of the primordial matter powerspectrum. This relation is unconstrained by observations on subgalactic scales. We derive the first measurement of the massconcentration relation using the image positions and flux ratios from eleven quadrupleimage strong gravitational lenses (quads) in the mass range 106 − 1010M⊙, assuming cold dark matter. We model both subhalos and line of sight halos, finitesize background sources, and marginalize over nuisance parameters describing the lens macromodel. We also marginalize over the the logarithmic slope and redshift evolution of the massconcentration relation, using flat priors that encompass the range of theoretical uncertainty in the literature. At z = 0, we constrain the concentration of 108M⊙ halos $c=12_{5}^{+6}$ at $68 \%$ CI, and $c=12_{9}^{+15}$ at $95 \%$ CI. For a 107M⊙ halo, we obtain $68 \%$ ($95 \%$) constraints $c=15_{8}^{+9}$ ($c=15_{11}^{+18}$), while for 109M⊙ halos $c=10_{4}^{+7}$ ($c=10_{7}^{+14}$). These results are consistent with the theoretical predictions from massconcentration relations in the literature, and establish strong lensing by galaxies as a powerful probe of halo concentrations on subgalactic scales across cosmologicalmore »

ABSTRACT The freestreaming length of dark matter depends on fundamental dark matter physics, and determines the abundance and concentration of dark matter haloes on subgalactic scales. Using the image positions and flux ratios from eight quadruply imaged quasars, we constrain the freestreaming length of dark matter and the amplitude of the subhalo mass function (SHMF). We model both main deflector subhaloes and haloes along the line of sight, and account for warm dark matter freestreaming effects on the mass function and mass–concentration relation. By calibrating the scaling of the SHMF with host halo mass and redshift using a suite of simulated haloes, we infer a global normalization for the SHMF. We account for finitesize background sources, and marginalize over the mass profile of the main deflector. Parametrizing dark matter freestreaming through the halfmode mass mhm, we constrain the thermal relic particle mass mDM corresponding to mhm. At $95 \, {\rm per\, cent}$ CI: mhm < 107.8 M⊙ ($m_{\rm {DM}} \gt 5.2 \ \rm {keV}$). We disfavour $m_{\rm {DM}} = 4.0 \,\rm {keV}$ and $m_{\rm {DM}} = 3.0 \,\rm {keV}$ with likelihood ratios of 7:1 and 30:1, respectively, relative to the peak of the posterior distribution. Assuming cold dark matter, we constrainmore »

ABSTRACT Core formation and runaway core collapse in models with selfinteracting dark matter (SIDM) significantly alter the central density profiles of collapsed haloes. Using a forward modelling inference framework with simulated datasets, we demonstrate that flux ratios in quadruple image strong gravitational lenses can detect the unique structural properties of SIDM haloes, and statistically constrain the amplitude and velocity dependence of the interaction crosssection in haloes with masses between 106 and 1010 M⊙. Measurements on these scales probe selfinteractions at velocities below $30 \ \rm {km} \ \rm {s^{1}}$, a relatively unexplored regime of parameter space, complimenting constraints at higher velocities from galaxies and clusters. We cast constraints on the amplitude and velocity dependence of the interaction crosssection in terms of σ20, the crosssection amplitude at $20 \ \rm {km} \ \rm {s^{1}}$. With 50 lenses, a sample size available in the near future, and flux ratios measured from spatially compact midIR emission around the background quasar, we forecast $\sigma _{20} \lt 11\rm {\small {}}23 \ \rm {cm^2} \rm {g^{1}}$ at $95 {{\ \rm per\ cent}}$ CI, depending on the amplitude of the subhalo mass function, and assuming cold dark matter (CDM). Alternatively, if $\sigma _{20} = 19.2 \ \rmmore »