arXiv subjects

Kiyun Yun

Publications and source records attributed to Kiyun Yun.

4 recordsLinked to original sources

arXiv2026

SN Ia Population Machine. I. A Unified Cosmological Simulation-Binary Synthesis Framework Establishing Non-universal Delay-time Distributions and Cosmic Progenitor-channel Dominance Crossover

We present a forward-modeling framework for synthesizing Type Ia supernova (SN Ia) populations by coupling cosmological hydrodynamic simulations to binary population synthesis (BPS). Using IllustrisTNG star particles as simple stellar populations, we generate binaries and evolve them with COMPAS to produce synthetic SNe Ia tagged with explosion times and progenitor channels (single- and double-degenerate; SD and DD). This cosmology-BPS pipeline enables self-consistent, end-to-end tracking of SN Ia populations from individual galaxies to cosmic scales. The model reproduces key SN-related observables, including host-galaxy demographics, delay-time distributions (DTDs), SN-rate trends with host properties and redshift, and a progenitor-age 'step' implicated by the mass step in Hubble residuals. Our main findings are as follows. (1) Contrary to the standard assumption, DTDs appear intrinsically non-universal: their form depends on progenitor channel and metallicity, and thus varies systematically across hosts and with redshift. The commonly adopted DTD is therefore best regarded as a population-averaged approximation rather than a fundamental kernel. (2) We predict that the dominant SN Ia progenitor population shifts from SD to DD with cosmic time, with a demographic crossover near z = 0.5 (~5.2 Gyr ago). This non-monolithic SN Ia population with a redshift-dependent SD/DD mixture weakens the universality implicit in a single globally calibrated standardization. Taken together, evolution in both the DTD and the channel mixture can imprint redshift-dependent systematics on SN Ia luminosities, strengthening the case for jointly inferring progenitor/host-driven effects alongside cosmic acceleration. The full catalogue and analysis scripts are available via Zenodo.

astro-ph.GA↗

arXiv2022

Warped Disk Galaxies. I. Linking U type Warps in Groups/Clusters to Jellyfish Galaxies

arped disk galaxies are classified into two morphologies: S- and U-types. Conventional theories routinely attribute both types to galactic tidal interaction and/or gas accretion, but reproducing of U-types in simulations is extremely challenging. Here we investigate whether both types are governed by the same mechanisms using the most extensive sample of $\sim$8000 nearby (0.02\,$<$\,z\,$<$\,0.06) massive ($M_{*}/M_{\odot}$\,$>$\,$10^9$) edge-on disks from SDSS. We find that U-types show on average bluer optical colors and higher specific star formation rate (sSFR) than S-types, with more strongly warped U-types having higher sSFR. We also find that while the S-type warp properties correlate with the tidal force by the nearest neighbor regardless of the environment, there is no such correlation for U-types in groups/clusters, suggesting a non-tidal environmental could be at play for U-types, such as ram pressure stripping (RPS). Indeed, U-types are more common in groups/clusters than in fields and they have stellar mass, gas fraction, sSFR enhancement and phase-space distribution closely analogous to RPS-induced jellyfish galaxies in clusters. We furthermore show that the stellar disks of most RPS galaxies in the IllustirsTNG simulation are warped in U-shape and bent in opposite direction of stripped gas tails, satisfying theoretical expectations for stellar warps embeded in jellyfishes. We therefore suggest that despite the majority of U-types that live in fields being still less explained, RPS can be an alternative origin for those in groups/clusters.

astro-ph.GA↗

arXiv2018

Jellyfish galaxies with the IllustrisTNG simulations: I. Gas-stripping phenomena in the full cosmological context

We use IllustrisTNG, a suite of gravity and MHD simulations, to study the demographics and properties of jellyfish galaxies in the full cosmological context. By jellyfish galaxies, we mean satellites orbiting in massive groups and clusters that exhibit highly asymmetric distributions of gas and gas tails. We use the TNG100 run and select galaxies at redshifts $z\le0.6$ with stellar mass exceeding $10^{9.5}{\rm M_\odot}$ and with host halo masses of $10^{13}-10^{14.6}\,{\rm M_\odot}$. Among more than about 6000 (2600) galaxies with stars (and some gas), we identify 800 jellyfish galaxies by visually inspecting their gas and stellar mass maps in random projections. About $31\%$ of cluster satellites are found with signatures of ram-pressure stripping and gaseous tails stemming from the main luminous bodies. This is a lower limit, since the random orientation entails a loss of about $30\%$ of galaxies that in an optimal projection would otherwise be identified as jellyfish. The connection with ram-pressure stripping is further confirmed by a series of findings: jellyfish galaxies are more frequent at intermediate and large cluster-centric distances ($r/R_{\rm 200c}\gtrsim 0.25$); they move through the ICM with larger bulk velocities and Mach numbers than the general cluster population, typically orbiting supersonically and experiencing larger ram pressures. Furthermore, the gaseous tails usually extend in opposite directions to the galaxy trajectory, with no relation between tail orientation and the host's center. The frequency of jellyfish galaxies shows a very weak dependence on redshift $(0\le z\le0.6)$ but larger fractions of disturbed gaseous morphologies occur in more massive hosts and at smaller satellite masses. Finally, jellyfish galaxies are late infallers ($< 2.5-3$ Gyrs ago, at $z=0$) and the emergence of gaseous tails correlates well with the presence of bow shocks in the ICM.

astro-ph.GA↗

arXiv2016

Odyssey: A Public GPU-Based Code for General-Relativistic Radiative Transfer in Kerr Spacetime

General-relativistic radiative transfer (GRRT) calculations coupled with the calculation of geodesics in the Kerr spacetime are an essential tool for determining the images, spectra and light curves from matter in the vicinity of black holes. Such studies are especially important for ongoing and upcoming millimeter/submillimeter (mm/sub-mm) Very Long Baseline Interferometry (VLBI) observations of the supermassive black holes at the centres of Sgr A^{*} and M87. To this end we introduce Odyssey, a Graphics Processing Unit(GPU)-based code for ray tracing and radiative transfer in the Kerr spacetime. On a single GPU, the performance of Odyssey can exceed 1 nanosecond per photon, per Runge-Kutta integration step. Odyssey is publicly available, fast, accurate, and flexible enough to be modified to suit the specific needs of new users. Along with a Graphical User Interface (GUI) powered by a video-accelerated display architecture, we also present an educational software tool, Odyssey_Edu, for showing in real time how null geodesics around a Kerr black hole vary as a function of black hole spin and angle of incidence onto the black hole.

astro-ph.HE↗