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Plasma surrounding a black hole modifies light propagation and can alter the observed shadow, potentially affecting the interpretation of Event Horizon Telescope data. We study the effects of dark matter and nonmagnetized pressureless plasma on the shadow of a Kerr-like black hole by analyzing null geodesics in both homogeneous and inhomogeneous plasma distributions. For the homogeneous plasma profile, the asymptotic Bardeen coordinates acquire a refractive normalization factor arising from the leading-order coupling between the metric function <inline-formula><mml:math><mml:mi>∆</mml:mi><mml:mo>(</mml:mo><mml:mi>r</mml:mi><mml:mo>)</mml:mo></mml:math></inline-formula> and the radial plasma function <inline-formula><mml:math><mml:msub><mml:mi>f</mml:mi><mml:mi>r</mml:mi></mml:msub><mml:mo>(</mml:mo><mml:mi>r</mml:mi><mml:mo>)</mml:mo><mml:mo>∝</mml:mo><mml:msup><mml:mi>r</mml:mi><mml:mn>2</mml:mn></mml:msup></mml:math></inline-formula>. We show that increasing the black hole spin generally enlarges the shadow radius and increases its deformation, while moving the observer away from the equatorial plane decreases both quantities. For the parameter ranges considered, astrophysically reasonable dark matter densities in this model do not produce appreciable changes in the photon trajectories. Plasma effects, however, are significant; increasing the plasma density increases the shadow radius and deformation for homogeneous plasma, but decreases them for inhomogeneous plasma. The energy emission rate likewise depends strongly on the plasma model, with homogeneous plasma producing a substantially larger rate as the plasma strength increases. As an illustrative benchmark, we compare the resulting geometric critical-curve sizes with EHT-inferred shadow-size intervals for M87* and Sgr A*.

Accreted stars in the Milky Way (MW) preserve information about their galaxies of origin in their chemo-dynamical properties. In this study, we use the chemo-dynamical signatures in the merger debris to approximate the posterior distribution of the properties of disrupted satellites at their accretion. Adopting a simulation-based inference framework, we train an ensemble of normalizing flows using samples of merger debris from the Auriga simulations. Applying this methodology to a local sample of accreted stars in the MW, we infer the lookback times, stellar and halo masses, and halo mass merger ratios of several known accretion events: Gaia-Enceladus-Sausage (GES), Helmi streams, Heracles, I'itoi, LMS-1/Wukong, Sagittarius, Sequoia, and Thamnos. Our predictions for accretion time and mass align with previous estimates and follow the expected stellar mass─metallicity relation across redshifts. The total accreted stellar mass from these events is predicted to be <inline-formula><tex-math>$2.2^{+1.1}_{-0.6}\times 10^{9}~\rm {M_{\odot }}$</tex-math></inline-formula>, with the GES and Sagittarius dwarfs being the largest contributors. The total accreted stellar mass from all disrupted progenitors is <inline-formula><tex-math>$1.4^{+1.1}_{-0.4}\times 10^{9}~\rm {M_{\odot }}$</tex-math></inline-formula>, which is consistent with previous mass measurements of this component. We provide a prediction for the evolution of the MW halo mass until the accretion of Sagittarius (<inline-formula><tex-math>$z\approx 1$</tex-math></inline-formula>): We find that the halo mass growth from the time of its first merger (<inline-formula><tex-math>$z\approx 5$</tex-math></inline-formula>) to <inline-formula><tex-math>$z\approx 2$</tex-math></inline-formula> significantly exceeds the total mass of the known progenitors accreted during that interval, suggesting the presence of unidentified substructures. Our estimate of the Galaxy halo mass after the Sagittarius merger, but prior to the accretion of the Magellanic Clouds, is <inline-formula><tex-math>$5.9^{+1.4}_{-1.1}\times 10^{11}~\rm {M_{\odot }}$</tex-math></inline-formula>.

We investigate the cosmological information in higher-order statistics of the cosmic microwave background (CMB) lensing convergence field for a near-term experiment with noise properties similar to the Simons Observatory (SO). Using a fully field-level forward-modeling pipeline based on ray-traced simulations from the MassiveNuS suite and realistic SO-like CMB lensing reconstruction, we naturally include nonlinear structure formation, post-Born effects, and higher-order reconstruction noise. We measure several non-Gaussian statistics, including Minkowski functionals, peak and minima counts, moments, and wavelet-scattering coefficients. We train Gaussian-process emulators to model each statistic's dependence on the matter density fraction <inline-formula><mml:math><mml:msub><mml:mi>Ω</mml:mi><mml:mi>m</mml:mi></mml:msub></mml:math></inline-formula>, the scalar power spectrum amplitude <inline-formula><mml:math><mml:msub><mml:mi>A</mml:mi><mml:mi>s</mml:mi></mml:msub></mml:math></inline-formula>, and the neutrino mass sum <inline-formula><mml:math><mml:msub><mml:mi>M</mml:mi><mml:mi>ν</mml:mi></mml:msub></mml:math></inline-formula>. We quantify the relative information gain these statistics provide beyond the lensing power spectrum and identify which are most robust to reconstruction noise. We find that morphology-based statistics, particularly Minkowski functionals and peak/minima counts, offer significant complementary constraining power: combining all non-Gaussian statistics with the power spectrum yields reductions of 40% and 38% in the marginalized uncertainties on <inline-formula><mml:math><mml:msub><mml:mi>Ω</mml:mi><mml:mi>m</mml:mi></mml:msub></mml:math></inline-formula> and <inline-formula><mml:math><mml:msub><mml:mi>A</mml:mi><mml:mi>s</mml:mi></mml:msub></mml:math></inline-formula>, respectively, and a 70% reduction in the one-sided uncertainty on <inline-formula><mml:math><mml:msub><mml:mi>M</mml:mi><mml:mi>ν</mml:mi></mml:msub></mml:math></inline-formula>. These gains remain non-negligible even when the power spectrum is extended to larger scales and combined with primary CMB and BAO data, with Minkowski functionals providing an additional 11% improvement in <inline-formula><mml:math><mml:mi>σ</mml:mi><mml:mo>(</mml:mo><mml:msub><mml:mi>M</mml:mi><mml:mi>ν</mml:mi></mml:msub><mml:mo>)</mml:mo></mml:math></inline-formula> and 35% in <inline-formula><mml:math><mml:mi>σ</mml:mi><mml:mo>(</mml:mo><mml:msub><mml:mi>Ω</mml:mi><mml:mi>m</mml:mi></mml:msub><mml:mo>)</mml:mo></mml:math></inline-formula> beyond the extended power spectrum. By contrast, moments and wavelet-scattering coefficients provide more limited gains at SO noise levels. Our results highlight the potential of non-Gaussian statistics to enhance cosmological constraints from SO and future CMB surveys.