arXiv subjects

Yuka Kaneda

Publications and source records attributed to Yuka Kaneda.

5 recordsLinked to original sources

arXiv2026

Formation of Parallel Stellar Streams through Encounters with Dark Matter Subhalos and Intermediate-Mass Black Holes

Dark matter subhalos and intermediate-mass black holes wandering in the Milky Way and the Andromeda galaxy are difficult to directly detect through electromagnetic observations, yet knowing their abundance is essential for understanding galaxy formation and evolution. We propose parallel stellar streams as dynamical imprints left on stellar streams by dark perturbers, including starless dark matter subhalos and wandering intermediate-mass black holes. We report that a single stream can split into two parallel structures after an encounter with a dark perturber. This scenario is supported by analytical modelling and N-body simulations. We also discuss how we can distinguish parallel stellar streams from other formation processes based on observables. We extend the theoretical picture of stream-subhalo interactions by showing that encounters with dark perturbers can generate density depletions perpendicular to the stream elongation, leading to parallel stellar stream morphologies beyond conventional gap-like signatures.

astro-ph.GA↗

arXiv2026

The Characteristic Mass and Energy Conversion Efficiency in the Cusp-Core Transition of Dark Matter Haloes: Implications for Scaling Relations and Supernova feedbacks

Galaxies in the nearby Universe, particularly dwarf systems, exhibit inner mass profiles of dark matter haloes that systematically depart from canonical cold dark matter expectations, signalling an interplay between baryonic feedback and the collisionless halo. We update an analytical cusp-core transition model by incorporating the effect of supernova-driven mass loss. Adapting this model to SPARC galaxies, we measure the energy conversion efficiency epsilon, defined as the fraction of supernova feedback energy that is used to change the central dark-matter potential. We find epsilon ~ 0.01 for nearby SPARC galaxies. Building on these measurements, we compare the dynamical energy required for a cusp-core transformation with the feedback energy available over burst cycles and identify a cusp-core transition forbidden region on the halo-stellar mass plane where transformation cannot occur. Galaxies with halo masses from 10^8 to 10^11 M_sun lie outside the forbidden region, whereas ultra-faint dwarf galaxies < 10^8 M_sun, galaxy groups and clusters > 10^11 M_sun fall within it, consistent with their high central densities and the inefficiency of core formation at very low and very high masses. This approach also explains the observed diversity of inner density profiles in low-mass systems, showing that both the star formation rate and the energy conversion efficiency govern them, with the latter emerging as a key parameter setting the strength of the cusp-core transition. Beyond the cusp-core problem, our observationally inferred energy conversion efficiency provides a model independent benchmark that strongly constrains galaxy formation models.

astro-ph.GA↗

arXiv2025

Cusp-to-Core Transition of Dark Matter Halos across Galaxy Mass Scales

We investigate the diversity of dark matter (DM) density profiles in a large sample of late-type galaxies from the SPARC database, with the goal of testing whether a cusp-to-core transition occurs across galaxy mass scales. We perform Bayesian fits to high-quality rotation curves using flexible halo models that allow for variations in the inner slopes of DM density profiles. We quantify the central dark matter structure using the surface density within the inner region of the halo, defined as $\Sigma_{\rm DM}(<0.01r_{V_{\rm max}})$, and compare the SPARC galaxies with Milky Way dwarf satellites as well as galaxy groups and clusters. Our results reveal significant diversity in the inner density slopes of SPARC galaxies, ranging from steep cusps to shallow cores, and show that many of them lie below the cuspy profiles predicted by the cold dark matter model, consistent with core-like structures. In contrast, both lower-mass dwarf galaxies and higher-mass galaxy clusters tend to follow the cuspy DM halos. These findings suggest that baryonic feedback may induce a cusp-to-core transition in Milky Way-mass galaxies, as predicted by hydrodynamical simulations. However, observational limitations and modeling uncertainties still prevent a definitive conclusion. This study provides new empirical insights into the halo mass-dependent nature of DM inner structures and the role of baryonic processes in shaping them.

astro-ph.GA↗

arXiv2024

Cosmological evolution of dark matter subhaloes under tidal stripping by growing Milky Way-like galaxies

We present the findings of a comprehensive and detailed analysis of merger tree data from ultra-high-resolution cosmological $N$-body simulations. The analysis, conducted with a particle mass resolution of $5 \times 10^3 h^{-1} M_{\odot}$ and a halo mass resolution of $10^7 h^{-1} M_{\odot}$, provides sufficient accuracy to suppress numerical artefacts. This study elucidates the dynamical evolution of subhaloes associated with the Milky Way-like host haloes. Unlike more massive dark matter haloes, which have been extensively studied, these subhaloes follow a distinct mass evolution pattern: an initial accretion phase, followed by a tidal stripping phase where mass is lost due to the tidal forces of the host halo. The transition from accretion to stripping, where subhaloes reach their maximum mass, occurs around a redshift of $z\simeq1$. Smaller subhaloes reach this point earlier, while larger ones do so later. Our analysis reveals that over 80 per cent of subhaloes have experienced mass loss, underscoring the universality of tidal stripping in subhalo evolution. Additionally, we derived the eccentricities and pericentre distances of subhalo orbits from the simulations and compare them with those of nearby satellite galaxies observed by the Gaia satellite. The results demonstrate a significant alignment between the orbital elements predicted by the cold dark matter model and the observed data, providing robust support for the model as a credible candidate for dark matter.

astro-ph.GA↗

arXiv2024

A universal scaling relation incorporating the cusp-to-core transition of dark matter haloes

The dark matter haloes associated with galaxies have hitherto established strong correlations within a range of observed parameters, known as scaling relations of dark matter haloes. The origin of these scaling relations still contains significant ambiguities and requires comprehensive exploration for complete understanding. Utilising the correlation between the concentration and mass of dark matter haloes inferred from cosmological $N$-body simulations based on the cold dark matter paradigm ($c$-$M$ relation), we derive theoretical scaling relations among other physical quantities such as the surface mass density, the maximum circular velocity, and the scale radius of the dark matter halo. By comparing theoretical and observed scaling relations at various mass scales, it is found that the scaling relations observed in dwarf galaxies and galaxies originate in the $c$-$M$ relation of the dark matter halo. We predict that this theoretical scaling relation is also established in galaxy clusters. Moreover, we propose a novel theoretical scaling relation that incorporates the effects of the cusp-to-core transition, which is supposed to occur in cold dark matter haloes. Our discussion concludes with the exploration of potential observational verification of the cusp-to-core transition process in dark matter haloes.

astro-ph.GA↗