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Polarized emission from dust and synchrotron radiation from the ISM are the dominant foregrounds for CMB polarization and are a major challenge for extracting the primordial signal on large angular scales. A key characteristic of the galactic foreground emission is its $EE/BB$ ratio. We argue that MHD shocks play an important role in setting the observed $EE/BB$ ratio. To support this, we first analyze quasi-linear magnetohydrodynamics (MHD) simulations to obtain an $EE/BB$ ratio that increases as $\sim k^2$, then show that with increasing energy injection rates, the $EE/BB$ ratio flattens to a value $\gtrsim 1$, approaching observational results. Looking at the distribution of the velocity divergence, a tail with power law $-7/2$ develops around the same injection rates where the $EE/BB$ ratio flattens. While the system becomes more isotropic, MHD shocks are intrinsically anisotropic and lead to the $E/B$ power asymmetry. We also observe total pressure balance among all our simulations, indicating slow wave dominance. Therefore, in the regime we consider, it is important to go beyond linear MHD equations to understand the foreground radiation.

The connection between $γ$-ray flares and blazars is a topic of active research, with few sources exhibiting distinct enough such outbursts to be able to conclusively connect them to features in their jet morphology. Here we present an investigation of the sole $γ$-ray flare of the blazar OJ 248 thus far, in association with its jet structure, as revealed by very long baseline interferometry (VLBI). We find that throughout the course of the $γ$-ray flare, the fractional linear polarisation increases in the jet of OJ 248, and the VLBI electric vector position angles (EVPAs) turn perpendicular to the bulk jet flow. We interpret this behaviour as a moving shock, travelling through a recollimation shock and upscattering photons via the inverse Compton scattering process, producing a $γ$-ray flare; we discuss possible mechanisms. Our hypothesised shock-shock interaction scenario is a viable mechanism to induce such EVPA rotations in both optical and radio bands.

We analyze the H2 emission observed in the HH46 Class I system as part of PROJECT-J (Protostellar Jets Cradle Tested with JWST), to investigate the origin and excitation of the warm molecular outflow. We used NIRSpec and MIRI spectral maps (1.6-27.9 microns) to trace the structure and physical conditions of the outflow. By fitting the H2 rotational diagrams with a multi-temperature gas model, we derived key physical parameters including temperature, extinction, column densities, and the ortho-to-para ratio. This information is combined with a detailed kinematical analysis and comparison with irradiated shock models. We find no evidence of H2 temperature or velocity stratification from the axis to the edge of the outflow, as would be expected in MHD disk-wind models and as observed in other outflows. Instead, the observations suggest that the H2 emission arises from shock interactions between jet bow shocks and/or wide-angle winds with the ambient medium and cavity walls. NIRSpec emission and velocity maps reveal expanding molecular shells, likely driven by the less luminous source in the binary system. We infer an accretion rate of less than 10^-9 solar masses per year for the seco

Exploring shock-shock interactions has been limited by experimental constraints, particularly in laser-induced shock experiments due to specialized equipment requirements. Herein, we introduce a tabletop approach to systematically investigate the excitation and superposition of dual laser-induced shock waves in water. Utilizing two laser pulses, spatio-temporally separated and focused into a confined water layer, we identify the optimal superposition leading to the highest combined shock pressure. Our results demonstrate that combining two shock waves each of $\sim$0.6~GPa pressure yields an overall shock pressure of $\sim$3~GPa. Our findings, suggesting an inherent nonlinear summation from the laser excitation process itself and highlights a new pathway for energy-efficient laser shock wave excitation.

The new era of galaxy evolution studies hearkened in by JWST has led to the discovery of z > 5 galaxies exhibiting excess nitrogen with log(N/O)~1 dex or more than expected from log(N/O) vs 12+log(O/H) trends in the local Universe. A variety of novel enrichment pathways have been presented to explain the apparent nitrogen excess, invoking a wide range of processes from very massive stars to stripped binaries to fine-tuned star-formation histories. However, understanding the excitation mechanism responsible for the observed nebular emission is necessary to accurately infer chemical abundances. As of yet, the ionization sources of these galaxies have not been thoroughly explored, with radiative shocks left out of the picture. We present a suite of homogeneous excitation models for star-forming galaxies, active galactic nuclei, and radiative shocks, with which we explore possible explanations for the apparent nitrogen excess. We propose new BPT-style diagnostics to classify galaxies at z > 5, finding that, when combined with O iii] 1660,66 and He ii 1640, N iii] 1747-54 / C iii] 1907,09 best selects shock-dominated galaxies while N iv] 1483,86 / C iii] 1907,09 best distinguishes

We calculate orbits, tidal radii, and bulge-bar and disk shocking destruction rates for 63 globular clusters in our Galaxy. Orbits are integrated in both an axisymmetric and a non-axisymmetric Galactic potential that includes a bar and a 3D model for the spiral arms. With the use of a Monte Carlo scheme, we consider in our simulations observational uncertainties in the kinematical data of the clusters. In the analysis of destruction rates due to the bulge-bar, we consider the rigorous treatment of using the real Galactic cluster orbit, instead of the usual linear trajectory employed in previous studies. We compare results in both treatments. We find that the theoretical tidal radius computed in the nonaxisymmetric Galactic potential compares better with the observed tidal radius than that obtained in the axisymmetric potential. In both Galactic potentials, bulge-shocking destruction rates computed with a linear trajectory of a cluster at its perigalacticons give a good approximation to the result obtained with the real trajectory of the cluster. Bulge-shocking destruction rates for clusters with perigalacticons in the inner Galactic region are smaller in the non-axisymmetric potent

Carrier wave shocking is studied using the Pseudo-Spectral Spatial Domain (PSSD) technique. We describe the shock detection diagnostics necessary for this numerical study, and verify them against theoretical shocking predictions for the dispersionless case. These predictions show Carrier Envelope Phase (CEP) and pulse bandwidth sensitivity in the single-cycle regime. The flexible dispersion management offered by PSSD enables us to independently control the linear and nonlinear dispersion. Customized dispersion profiles allow us to analyze the development of both carrier self-steepening and shocks. The results exhibit a marked asymmetry between normal and anomalous dispersion, both in the limits of the shocking regime and in the (near) shocked pulse waveforms. Combining these insights, we offer some suggestions on how carrier shocking (or at least extreme self-steepening) might be realised experimentally.

Using the adaptive mesh refinement code MG, we perform 3D hydrodynamic simulations of a supernova-cloud interaction in the "large cloud regime". The cloud is initially atomic and evolving due to the thermal instability (TI) and gravity. We study interactions in a "pre-TI" and "post-TI" stage when cold and dense clumps are present, and compare these results to idealised shock-cloud scenarios in the "small cloud regime", and a scenario without shocks. On aggregate, the supernova disruption is significantly weaker than that from an idealised shock due to the supernova impact being instantaneous, and not continuous. In both supernova-cloud interactions, we observe two shocks impact the cloud, followed by the development of a weak 10 km s$^{-1}$ upstream flow on the cloud interface, and a global ambient pressure drop. When the cloud is still atomic, it expands due to this drop. Additionally, the TI is triggered at the front of the cloud, causing the formation of a cap-like structure with clumps embedded inside. The upstream flow converges in this region, resulting in a lobe-like cloud morphology. When the cloud is molecular, the transmitted shock disrupts the inter-clump material and ca

I propose a definition for a "shocking coefficient" $S$ intended to make determinations of the degree of waveform shocking, and comparisons thereof, more quantitative. This means we can avoid having to make ad hoc judgements on the basis of the visual comparison of wave profiles.

A new theory of gravitational shocking based on time-dependent perturbation theory shows that the changes in energy and angular momentum due to a slowly varying disturbance are not exponentially small for stellar dynamical systems in general. It predicts significant shock heating by slowly varying perturbations previously thought to be negligible according to the adiabatic criterion. The theory extends the scenarios traditionally computed only with the impulse approximation and is applicable to a wide class of disturbances. The approach is applied specifically to the problem of disk shocking of star clusters.

The cold dark matter (CDM) scenario predicts that galactic halos should host a huge amount of subhalos possibly lighter than planets, depending on the nature of dark matter. Predicting their abundance and distribution has important implications for dark matter searches and searches for subhalos themselves, as they could provide a decisive test of the CDM paradigm. A major difficulty in subhalo population model building is to account for the gravitational stripping induced by baryons, which strongly impact on the overall dynamics inside galaxies. In this paper, we focus on these "baryonic" tides from analytical perspectives, summarizing previous work on galactic disk shocking, and thoroughly revisiting the impact of individual encounters with stars. For the latter, we go beyond the reference calculation of Gerhard and Fall (1983) to deal with penetrative encounters, and provide new analytical results. Based upon a full statistical analysis of subhalo energy change during multiple stellar encounters possibly occurring during disk crossing, we show that subhalos lighter than $\sim 1$~M$_\odot$ are very efficiently pruned by stellar encounters. This modifies their mass function in a st

Researchers have shown that blending quantum computing with AI can dramatically improve predictions of complex, chaotic systems。 By letting a quantum computer identify hidden patterns in data, the AI becomes more accurate and stable over time。 The method outperformed standard models while using far less memory

Using HST/COS/STIS and HIRES/Keck high-resolution spectra, we have studied a remarkable HI absorbing complex at z=0.672 toward the quasar Q1317+277. The HI absorption has a velocity spread of 1600 km/s, comprises 21 Voigt profile components, and resides at an impact parameter of D=58 kpc from a bright, high mass [log(M_vir/M_sun) ~ 13.7] elliptical galaxy that is deduced to have a 6 Gyr old, solar metallicity stellar population. Ionization models suggest the majority of the structure is cold gas surrounding a shock heated cloud that is kinematically adjacent to a multi-phase group of clouds with detected CIII, CIV and OVI absorption, suggestive of a conductive interface near the shock. The deduced metallicities are consistent with the moderate in situ enrichment relative to the levels observed in the z ~ 3 Ly-alpha forest. We interpret the HI complex as a metal-poor filamentary structure being shock heated as it accretes into the halo of the galaxy. The data support the scenario of an early formation period (z > 4) in which the galaxy was presumably fed by cold-mode gas accretion that was later quenched via virial shocking by the hot halo such that, by intermediate redshift, the

Representative results of a search for structures suggestive of shocked gas in the circumnuclear regions of Seyfert galaxies are presented. At issue is whether we can identify regions that appear to be shocked by outflows from the active nucleus. Such regions will be good targets for future spectrophotometric studies to determine what role shocks play in the physics of the AGN/host galaxy interaction.