arXiv subjects

Daneng Yang

Publications and source records attributed to Daneng Yang.

At least 19 recordsLinked to original sources

arXiv2026

Path Measures for Stochastic Galaxy Formation on Layered Halo Graphs

Galaxy formation, viewed as an inference problem from incomplete information, is inherently stochastic. Reducing the full simulation state to a coarse-grained set of variables integrates out unresolved degrees of freedom, motivating an effective stochastic description of galaxy formation in reduced variables. Existing approaches have achieved substantial predictive success, but generally lack a unified statistical framework for trajectory-level galaxy assembly and history-conditioned fluctuations. We introduce a Graph Path Likelihood Model that formulates galaxy assembly histories as stochastic dynamical trajectories on hierarchical halo merger graphs, where temporal edges encode causal transport and coeval host edges encode environmental conditioning. Within this formulation, galaxy evolution is described by graph-conditioned path measures and effective actions, from which observables, likelihoods, and response diagnostics emerge from a common probabilistic description. As a first realization, we train a graph neural likelihood model for stellar and gas mass assembly histories on layered halo graphs extracted from hydrodynamic simulations. We show that it reproduces the main statistics of these histories while capturing environmentally conditioned correlated fluctuations. The path measure formulation also provides a natural setting for example fixed-graph applications, which we illustrate with the fraction of dark-matter-deficient galaxies, controlled gas-response deformations, and nonequilibrium diagnostics of environmentally dependent evolution. In particular, the present construction also admits extensions in which merger-history statistics and baryonic evolution are treated within a unified probabilistic description, potentially enabling studies of how graph structure, assembly histories, and galaxy observables respond jointly to variations in the underlying theory.

astro-ph.GA↗

arXiv2026

Flux-ratio anomalies in cusp quasars reveal dark matter beyond CDM

Strongly lensed quasars in cusp configurations provide a uniquely sensitive probe of small-scale dark matter structure. Using the largest microlensing-free flux ratios for 17 quadruply imaged cusps, we combine these with extensive Monte Carlo simulations of mock lens realizations under cold dark matter (CDM), self-interacting dark matter (SIDM), and fuzzy dark matter (FDM) scenarios. Building on this, we propose a region (minor-axis and narrow major-axis cusp lenses) where flux-ratio anomalies persist even under globally parameterized models ("macromodels") with multipole freedom (capturing disk, asymmetric, or merger-driven structures). Within this region, J1042+1641 is $>3\sigma$ incompatible with both CDM and SIDM. Our results yield a Bayes factor exceeding $100$, providing very strong evidence for FDM over even the most optimistic CDM and SIDM scenarios. As only 11 cusp lenses lie within this region, extending to larger samples will be essential for assessing its statistical generality and for decisively confirming these findings with future microlensing-free flux ratio data.

astro-ph.CO↗

arXiv2025

Dark-Matter-Deficient Galaxies from Collisions: A New Probe of Bursty Feedback and Dark Matter Physics

High-velocity collisions between gas-rich ultra-diffuse galaxies present a promising formation channel for dark-matter-deficient galaxies (DMDGs). Using hydrodynamical simulations, we show that the progenitors' baryonic binding energy, $|E_{\rm bind}|$, critically controls the outcome. Repeated potential fluctuations, e.g., from bursty feedback, inject energy and reduce $|E_{\rm bind}|$ by $\approx 15\%$, yielding fewer but substantially more massive DMDGs. By contrast, elastic self-interacting dark matter (SIDM) produces comparable cores without lowering $|E_{\rm bind}|$, perturbing DMDG masses without clear enhancement. This differs from what happens in host halos, where SIDM-induced cores enhance dark matter tidal stripping while keeping baryons compact and resilient to tidal effects. The contrasting roles of SIDM may provide a means to distinguish feedback-formed halo cores from those created by SIDM. Among 15 paired simulation runs, 13 show higher DMDG masses in the weakened-binding case, and about two thirds exhibit $>100\%$ mass enhancements. The simulations also predict systematically lower gas fractions due to sustained post-collision star formation, yielding a clean observational signature. Upcoming wide-field imaging (CSST, LSST), HI surveys (FAST), and kinematic follow-up will be crucial to test this scenario.

astro-ph.GA↗

arXiv2025

Self-Interacting Dark Matter with Mass Segregation: A Unified Explanation of Dwarf Cores and Small-Scale Lenses

In two-component self-interacting dark matter (SIDM) models with inter-species interactions, mass segregation arises naturally from collisional relaxation, enhancing central densities and gravothermal evolution. We demonstrate that models with velocity-dependent interactions, both within and between species, can connect several small-scale observations while remaining consistent with cluster-scale constraints. This combination enables core formation in dwarf halos, where the presence of baryons increases the inner densities and enhances the predicted strong lensing signatures. Using cosmological and controlled simulations alongside an accurate parametric model, we present proof-of-principle examples showing that this framework can explain the structure of dark perturbers observed in strong lensing systems, and can enhance the efficiency of small-scale lenses by a factor of a few, in line with the excess reported in galaxy-galaxy strong-lensing observations. Importantly, mass segregation can enhance the Einstein radii of SIDM halos relative to their cold dark matter (CDM) counterparts, overcoming a key challenge in one-component SIDM scenarios. Our results present mass segregation in two-component SIDM as a self-consistent, testable framework with the potential to address multiple small-scale challenges in structure formation.

astro-ph.CO↗

arXiv2025

Diversifying halo structures in two-component self-interacting dark matter models via mass segregation

Self-interacting dark matter (SIDM), through gravothermal evolution driven by elastic self-scatterings, offers a compelling explanation for the observed diversity of inner halo densities. In this work, we investigate SIDM dynamics in a two-component dark matter model with mass ratios of order unity, motivated by an asymmetric dark matter framework that naturally evades constraints from relic abundance and mediator decay, while enabling strong, velocity-dependent self-interactions. We show that cross-component scatterings significantly enhance mass segregation, driving the formation of dense, core collapsed-like halos. This effect couples naturally to SIDM-induced diversity, introducing a new mechanism for generating structural variations beyond those arising from gravothermal evolution alone. Our results reveal a novel mechanism for reconciling SIDM with small-scale observational tensions by enabling shifts in central densities while preserving the flexibility to generate diverse halo structures. We further highlight that halo structural diversity may serve as a diagnostic of dark sector composition, opening a new observational window into the particle nature of SIDM.

astro-ph.CO↗

arXiv2025

SIDM Concerto: Compilation and Data Release of Self-interacting Dark Matter Zoom-in Simulations

We present SIDM Concerto: $14$ cosmological zoom-in simulations in cold dark matter (CDM) and self-interacting dark matter (SIDM) models based on the Symphony and Milky Way-est suites. SIDM Concerto includes one Large Magellanic Cloud- (LMC-) mass system (host mass $\sim 10^{11}~M_{\mathrm{\odot}}$), two Milky Way (MW) analogs ($\sim 10^{12}~M_{\mathrm{\odot}}$), two group-mass hosts ($\sim 10^{13}~M_{\mathrm{\odot}}$), and one low-mass cluster ($\sim 10^{14}~M_{\mathrm{\odot}}$). Each host contains $\approx 2\times 10^7$ particles and is run in CDM and one or more strong, velocity-dependent SIDM models. Our analysis of SIDM (sub)halo populations over seven subhalo mass decades reveals that (1) the fraction of core-collapsed isolated halos and subhalos peaks at a maximum circular velocity corresponding to the transition of the SIDM cross section from a $v^{-4}$ to $v^0$ scaling; (2) SIDM subhalo mass functions are suppressed by $\approx 50\%$ relative to CDM in LMC, MW, and group-mass hosts but are consistent with CDM in the low-mass cluster host; (3) subhalos' inner density profile slopes, which are more diverse in SIDM than in CDM, are sensitive to both the amplitude and shape of the SIDM cross section. Our simulations provide a benchmark for testing SIDM predictions with astrophysical observations of field and satellite galaxies, strong lensing systems, and stellar streams. Data products are publicly available at https://doi.org/10.5281/zenodo.14933624.

astro-ph.CO↗

arXiv2025

A Universal Analytic Model for Gravitational Lensing by Self-Interacting Dark Matter Halos

We present a model for analytically calculating gravitational lensing by self-interacting dark matter (SIDM) halos. Leveraging the universal behavior of SIDM halos during gravothermal evolution, we calibrate the lensing potential using a fluid simulation, normalizing the evolution time to align with established scenarios. From this potential, we derive explicit equations for the deflection angle and surface density profile, quantifying their deviations from numerical results. Our model builds on the parametric approach of arXiv:2305.16176, providing refinements in the deep core-collapse regime and enabling more comprehensive lensing studies. We explore characteristic lensing features, including critical curves and caustics, for SIDM halos in isolation and within a main halo, tracking their evolution through the gravothermal phase. We also examine signatures in the self-similar regime of core collapsed halos and highlight the role of baryonic effects in realistic halos. The application of our model extends to generic halos, whose profiles fit one or a superposition of our parametric forms. We make our implementation publicly available on https://github.com/HouSiyuan2001/SIDM_Lensing_Model to support further research.

astro-ph.CO↗

arXiv2024

COZMIC. III. Cosmological Zoom-in Simulations of Self-interacting Dark Matter with Suppressed Initial Conditions

We present eight cosmological dark matter (DM)--only zoom-in simulations of a Milky Way--like system that include suppression of the linear matter power spectrum $P(k)$, and/or velocity-dependent DM self-interactions, as the third installment of the COZMIC suite. We consider a model featuring a massive dark photon that mediates DM self-interactions and decays into massless dark fermions. The dark photon and dark fermions suppress linear matter perturbations, resulting in dark acoustic oscillations in $P(k)$, which ultimately affect dwarf galaxy scales. The model also features a velocity-dependent elastic self-interaction between DM particles (SIDM), with a cross section that can alleviate small-scale structure anomalies. For the first time, our simulations test the impact of $P(k)$ suppression on gravothermal evolution in an SIDM scenario that leads to core collapse in (sub)halos with present-day virial masses below $\approx 10^9~M_{\mathrm{\odot}}$. In simulations with $P(k)$ suppression and self-interactions, the lack of low-mass (sub)halos and the delayed growth of structure reduce the fraction of core-collapsed systems relative to SIDM simulations without $P(k)$ suppression. In particular, $P(k)$ suppression that saturates current warm DM constraints almost entirely erases core collapse in isolated halos. Models with less extreme $P(k)$ suppression produce core collapse in $\approx 20\%$ of subhalos and $\approx 5\%$ of isolated halos above $10^8~M_{\mathrm{\odot}}$, and also increase the abundance of extremely low-concentration isolated low-mass halos relative to SIDM. These results reveal a complex interplay between early and late-Universe DM physics, revealing new discovery scenarios in the context of upcoming small-scale structure measurements.

astro-ph.CO↗

arXiv2024

The GD-1 stellar stream perturber as a core-collapsed self-interacting dark matter halo

The GD-1 stellar stream exhibits spur and gap structures that may result from a close encounter with a dense substructure. When interpreted as a dark matter subhalo, the perturber is denser than predicted in the standard cold dark matter (CDM) model. In self-interacting dark matter (SIDM), however, a halo could evolve into a phase of gravothermal collapse, resulting in a higher central density than its CDM counterpart. We conduct high-resolution controlled N-body simulations to show that a collapsed SIDM halo could account for the GD-1 perturber's high density. We model a progenitor halo with a mass of $3\times10^8~M_\odot$, motivated by a cosmological simulation of a Milky Way analog, and evolve it in the Milky Way's tidal field. For a cross section per mass of $\sigma/m\approx30-100~{\rm cm^2~g^{-1}}$ at $V_{\rm max }\sim10~{\rm km~s^{-1}}$, the enclosed mass of the SIDM halo within the inner $10~{\rm pc}$ can be increased by more than an order of magnitude compared to its CDM counterpart, leading to a good agreement with the properties of the GD-1 perturber. Our findings indicate that stellar streams provide a novel probe into the self-interacting nature of dark matter.

astro-ph.GA↗

arXiv2024

EDEN: Exploring Disks Embedded in N-body simulations of Milky-Way-mass halos from Symphony

We investigate the impact of galactic disks on the tidal stripping of cold dark matter subhalos within Milky Way (MW)-mass halos ($M_{\rm vir}\sim 10^{12}\mathrm{M_{\odot}}$) using a new simulation suite, EDEN. By re-simulating 45 MW-mass zoom-in halos from the N-body Symphony compilation with embedded disk potentials, which evolve according to star formation histories predicted by the UniverseMachine model, we self-consistently tie disk growth to halo accretion rate and significantly expand the range of disk masses and formation histories studied. We use the particle-tracking-based subhalo finder Symfind to enhance the robustness of subhalo tracking. We find that disks near the median disk-to-halo mass ratio of our sample ($M_{\ast, \rm Disk}/M_{\rm vir, host} = 2\%$) reduce subhalo peak mass functions within 100 kpc by about $10\%$ for peak masses above $ 10^8\mathrm{M_{\odot}}$. Heavier, MW/M31-like disks ($M_{\ast, \rm Disk}/M_{\rm vir, host} \gtrsim 5\%$) lead to a reduction of more than $40\%$. Subhalo abundance suppression is more pronounced near halo centers, with particularly enhanced stripping for subhalos accreted over 8 Gyr ago on orbits with pericenters < 100 kpc. Suppression is further amplified when disk mass is increased within fixed halo and disk assembly histories. In all cases, the suppression we measure should be interpreted as stripping below the mass resolution limit rather than complete subhalo disruption. This study reshapes our understanding of the MW's impact on its satellites, suggesting it strips subhalos more efficiently than typical MW-mass galaxies due to its larger disk-to-halo mass ratio and earlier disk formation.

astro-ph.GA↗

arXiv2024

Testing the parametric model for self-interacting dark matter using matched halos in cosmological simulations

We systemically evaluate the performance of the self-interacting dark matter (SIDM) halo model proposed in arXiv:2305.16176 with matched halos from high-resolution cosmological CDM and SIDM simulations. The model incorporates SIDM effects along mass evolution histories of CDM halos and it is applicable to both isolated halos and suhbhalos. We focus on the accuracy of the model in predicting halo density profiles at $z=0$ and the evolution of maximum circular velocity. We find the model predictions agree with the simulations within $10\%-50\%$ for most of the simulated (sub)halos, $50\%-100\%$ for extreme cases. This indicates that the model effectively captures the gravothermal evolution of the halos with very strong, velocity-dependent self-interactions. For an example application, we apply the model to study the impact of various SIDM scenarios on strong lensing perturber systems, demonstrating its utility in predicting SIDM effects for small-scale structure analyses. Our findings confirm that the model is an effective tool for mapping CDM halos into their SIDM counterparts.

astro-ph.CO↗

arXiv2024

Exploring Self-Interacting Dark Matter Halos with Diverse Baryonic Distributions: A Parametric Approach

Galaxies residing in dark matter halos exert significant gravitational effects that alter halo structure and dynamics. The complexity of these interactions escalates with the diversity of galactic structures and the variability in dark matter halo profiles under self-interacting dark matter (SIDM) models. This work extends the parametric model for dark matter-only halos presented in arXiv:2305.16176 to incorporate baryons. We adapt this model to consistently represent the SIDM halo density profile over time, highlighting the role of a gravothermal phase in characterizing the state of an SIDM halo. Given this phase, the density profile in SIDM is determined by a fictitious progenitor -- consisting of an NFW halo influenced by a baryonic potential -- that has evolved to its present state. In the temporal dimension, the model incorporates a form factor that rescales the evolution time in the dark matter-only case, thereby enabling the introduction of a universal phase. In the radial dimension, the halo density profile is parametrized to reflect the influences of baryons. We calibrate the model through N-body simulations with baryon potentials to fit various stellar-to-halo mass ratios and size-mass relationships. Our parametric approach is numerically efficient, enabling the exploration of SIDM effects across a diverse set of halos, as exemplified by a case study using an illustrative sample that spans five orders of magnitude in the mass range. We also demonstrate that the effects of evolution history and the specific SIDM model can be separated from the current states of galaxies and halos, leaving the task of identifying consistent SIDM models to dedicated post-processing analyses.

astro-ph.CO↗

arXiv2024

SASHIMI-SIDM: Semi-analytical subhalo modelling for self-interacting dark matter at sub-galactic scales

We combine the semi-analytical structure formation model, SASHIMI, which predicts subhalo populations in collisionless, cold dark matter (CDM), with a parametric model that maps CDM halos to self-interacting dark matter (SIDM) halos. The resulting model, SASHIMI-SIDM, generates SIDM subhalo populations down to sub-galactic mass scales, for an arbitrary input cross section, in minutes. We show that SASHIMI-SIDM agrees with SIDM subhalo populations from high-resolution cosmological zoom-in simulations in resolved regimes. Crucially, we predict that the fraction of core-collapsed subhalos peaks at a mass scale determined by the input SIDM cross section and decreases toward higher halo masses, consistent with the predictions of gravothermal models and cosmological simulations. For the first time, we also show that the core-collapsed fraction decreases toward lower halo masses. While the dependence of the collapse time on mass and concentration implies such behaviour, our semi-analytical approach allows us to quantify and illustrate this trend clearly across the full mass spectrum of subhalos, including for subhalo masses below the resolution limit of any current cosmological SIDM simulation. As a proof of principle, we apply SASHIMI-SIDM to predict the boost to the local dark matter density and annihilation rate from core-collapsed SIDM subhalos, which can be enhanced relative to CDM by an order of magnitude for viable SIDM models. Thus, SASHIMI-SIDM provides an efficient and reliable tool for scanning SIDM parameter space and testing it with astrophysical observations. The code is publicly available at https://github.com/shinichiroando/sashimi-si.

astro-ph.CO↗

arXiv2024

CDM and SIDM Interpretations of the Strong Gravitational Lensing Object JWST-ER1

van Dokkum et al. (arXiv:2309.07969) reported the discovery of JWST-ER1, a strong lensing object at redshift $z\approx2$, using data from the James Webb Space Telescope. The lens mass within the Einstein ring is $5.9$ times higher than the expected stellar mass from a Chabrier initial mass function, indicating a high dark matter density. In this work, we show that a cold dark matter halo, influenced by gas-driven adiabatic contraction, can account for the observed lens mass. We interpret the measurement of JWST-ER1 in the self-interacting dark matter scenario and show that the cross section per particle mass $\sigma/m\approx0.1~{\rm cm^2/g}$ is generally favored. Intriguingly, $\sigma/m\approx0.1~{\rm cm^2/g}$ can also be consistent with the strong lensing observations of early-type galaxies at redshift $z\approx0.2$, where adiabatic contraction is not observed overall.

astro-ph.GA↗

arXiv2024

Self-interacting dark matter interpretation of Crater II

The satellite galaxy Crater II of the Milky Way is extremely cold and exceptionally diffuse. These unusual properties are challenging to understand in the standard model of cold dark matter. We investigate the formation of Crater II in self-interacting dark matter (SIDM), where dark matter particles can scatter and thermalize. We conduct a series of controlled N-body simulations to model the tidal evolution of Crater II, varying the self-interacting cross section, orbit parameters, and initial stellar distribution. Dark matter self-interactions lead to halo core formation and the distribution of stars expands accordingly. A cored SIDM halo also boosts tidal mass loss, allowing for a high orbit. Our simulations show that SIDM halos with a $1~{\rm kpc}$ core can simultaneously explain the low stellar velocity dispersion and the large half-light radius of Crater II, remaining robust to the initial distribution of stars. For the orbit motivated by the measurements from Gaia Early Data Release 3, the favored self-interacting cross section is approximately $60~{\rm cm^2/g}$ on the mass scale of Crater II.

astro-ph.GA↗

arXiv2023

Enhanced Early Galaxy Formation in JWST from Axion Dark Matter?

We demonstrate that enhanced early galaxy formation can generically arise in axion-like particle (ALP) dark matter (DM) models with a delayed onset of axion field oscillation. In these models, the formation of localized massive objects enhances structure formation, potentially addressing the excess recently observed by the James Webb Space Telescope (JWST), while remaining consistent with existing constraints. We identify viable parameter space with the ALP mass in the range of $10^{-22}~{\rm eV}<m_a<10^{-19}~\rm eV$. In addition, we show that the ALP parameter regions of interest can lead to intriguing complementary signatures in the small-scale structure of DM halos and existing experimental searches for ALPs.

hep-ph↗

arXiv2023

The impact of baryonic potentials on the gravothermal evolution of self-interacting dark matter haloes

The presence of a central baryonic potential can have a significant impact on the gravothermal evolution of self-interacting dark matter (SIDM) haloes. We extend a semi-analytical fluid model to incorporate the influence of a static baryonic potential and calibrate it using controlled N-body simulations. We construct benchmark scenarios with varying baryon concentrations and different SIDM models, including constant and velocity-dependent self-interacting cross sections. The presence of the baryonic potential induces changes in SIDM halo properties, including central density, core size, and velocity dispersion, and it accelerates the halo's evolution in both expansion and collapse phases. Furthermore, we observe a quasi-universality in the gravothermal evolution of SIDM haloes with the baryonic potential, resembling a previously known feature in the absence of the baryons. By appropriately rescaling the physical quantities that characterize the SIDM haloes, the evolution of all our benchmark cases exhibits remarkable similarity. Our findings offer a framework for testing SIDM predictions using observations of galactic systems where baryons play a significant dynamical role.

astro-ph.CO↗

arXiv2023

A Self-interacting Dark Matter Solution to the Extreme Diversity of Low-mass Halo Properties

The properties of low-mass dark matter (DM) halos appear to be remarkably diverse relative to cold, collisionless DM predictions, even in the presence of baryons. We show that self-interacting DM (SIDM) can simultaneously explain observations of halo diversity at two opposite extremes$-$the inner density profile of the dense substructure perturbing the strong lens galaxy SDSSJ0946+1006 and the rotation curves of isolated, gas-rich ultradiffuse galaxies (UDGs). To achieve this, we present the first cosmological zoom-in simulation featuring strong DM self-interactions in a galaxy group environment centered on a $10^{13}~M_{\mathrm{\odot}}$ host halo. In our SIDM simulation, most surviving subhalos of the group-mass host are deeply core-collapsed, yielding excellent candidates for the observed dense strong-lens perturber. Self-interactions simultaneously create kiloparsec-scale cores in low-concentration isolated halos, which could host the observed UDGs. Our scenario can be further tested with observations of DM structure and galaxies over a wide mass range.

astro-ph.GA↗