The radioisotope 44Ti is produced through α-rich freezeout and explosive helium burning in type Ia supernovae (SNe Ia). In this paper, we discuss how the detection of 44Ti, either through late-time light curves of SNe Ia, or directly via gamma-rays, can uniquely constrain the origin of SNe Ia. In particular, building upon recent advances in the hydrodynamical simulation of helium-ignited double white dwarf binaries, we demonstrate that the detection of 44Ti in a nearby SN Ia or in a young Galactic supernova remnant (SNR) can discriminate between the double-detonation and double-degenerate channels of sub-Chandrasekhar (sub-MCh) and near-Chandrasekhar (near-MCh) SNe Ia. In addition, we predict that the late-time light curves of calcium-rich transients are entirely dominated by 44Ti.
SPP Proceedings
Steady-state density perturbations induced by a point mass in a finite cylinder
Mark Ivan Ugalino, and Michael Francis Ian G Vega
Proceedings of the 38th Samahang Pisika ng Pilipinas, Feb 2020
We consider a massive point particle moving along a circular orbit, immersed in a finite cylindrical gaseous environment, as a model for astrophysical compact objects embedded in a gaseous disk. We compute, via a frequency-domain calculation, the density perturbation induced by the gravitational influence of the perturber as a first-approximation to the full hydrodynamical problem.
SPP Proceedings
Density perturbations in a collisional fluid induced by a particle on a slightly-eccentric orbit
Mark Ivan Ugalino, and Michael Francis Ian Vega
Proceedings of the 36th Samahang Pisika ng Pilipinas, Feb 2018
We consider a massive perturber moving along slightly-eccentric orbits through a collisional fluid in flat spacetime. We compute, via a frequency-domain calculation, the density perturbations induced by this massive perturber and reproduce the characteristic spiral wave structure previously computed for circular orbits with time-domain methods. These are needed for extending Barausse’s perturbation analysis of relativistic dynamical friction effects on bodies moving through collisional fluids.
Preprints
arXiv
Towards robust simulations of the galactic dynamo: a cross-code comparison between Eulerian and Lagrangian schemes
Mark Ivan Ugalino, Benedikt Diemer, Vadim A. Semenov, and 8 more authors
Galactic magnetic fields are thought to be seeded by microscopic processes such as the Biermann battery and are primarily amplified to observed microgauss strengths by dynamo processes. Much of this amplification likely occurs within proto-galaxies, where turbulent and rotational kinetic energy is converted into magnetic energy via dynamo action. However, two aspects of this process remain poorly constrained in simulations: the saturation level of the amplified field and the timescale on which it is reached. In particular, different numerical methods, resolution strategies, and subgrid prescriptions have not converged to similar results, making it difficult to establish robust, code-independent conclusions about dynamo amplification in galaxies. In this work, we present the first systematic comparison of both Eulerian and Lagrangian codes that employ diverse MHD schemes, including ART, RAMSES, AREPO, and SWIFT. Using identical initial conditions for Milky Way-type galaxies and without including star formation and stellar feedback, we find that the amplification history of the magnetic field within the galactic disk depends strongly on the choice of hydrodynamical scheme, with orders-of-magnitude differences between Eulerian and Lagrangian approaches. We further demonstrate that reducing the mesh velocity in the moving-mesh code AREPO leads to results consistent with those obtained using the static grid codes ART and RAMSES. These results highlight the importance of carefully assessing numerical effects when interpreting magnetic field amplification in galaxy simulations.
arXiv
First-Principles Turbulence-Driven Deflagration-to-Detonation Transition Mechanism for Near-Chandrasekhar Mass White Dwarf Progenitors
Krut Patel, Robert Fisher, Alexei Poludnenko, and 3 more authors
Type Ia supernovae (SNe Ia) play an important role throughout astrophysics, most notably as standardizable cosmological candles. Yet, their stellar progenitors and explosion mechanism remain areas of active investigation. For decades, the canonical model for normal brightness SNe Ia used in cosmology was a carbon-oxygen white dwarf (WD) accreting from a non-degenerate stellar companion, approaching the Chandrasekhar mass (M_Ch). Previously, all models of near-M_Ch SNe Ia invoked an ad hoc assumption on the critical process of detonation initiation, and could therefore be tuned to a variety of outcomes. Here, we present global 3D hydrodynamical simulations of near-M_Ch progenitors, which incorporate, for the first time, a laboratory-validated ab initio mechanism for the turbulence-driven deflagration-to-detonation transition (tDDT). The tDDT detonation mechanism is highly efficient, leading to detonation initiation which is prompt in comparison to most prior work. Despite spanning a factor of six in central ignition density and qualitatively distinct ignition topologies, all models converge on nearly identical synthetic spectra at peak luminosity, spectroscopically matched to the overluminous SN 1999aa. The turbulence-driven Chapman-Jouguet criterion drives each progenitor to a common detonation configuration from diverse initial conditions, providing a physical foundation for the ignition-insensitive detonation outcomes implicit in the empirical standardizability of SNe Ia. This provides the first physically motivated, self-consistent pathway for delayed detonation in SNe Ia simulations. Further work is necessary to understand how this mechanism might produce more delayed detonation initiation and potentially fail, thereby yielding SNe Iax.
Conference Proceedings
AAS Conference
Galaxy clusters as dark matter laboratories
Benedikt Diemer, Alexie Leauthaud, Matthew DeMartino, and 5 more authors
In American Astronomical Society Meeting Abstracts #245, Jan 2025
The structure of dark halos carries signatures of their mass, dynamical state, and the nature of dark matter itself. Some of the most constraining signals can be found in the outskirts of galaxy clusters, which have recently become observationally accessible via the distribution of satellite galaxies, weak lensing, and the SZ effect. To harness the rapid progress promised by future instruments such as LSST and Roman, we need to understand which signals can realistically tell us about halos and the nature of dark matter. I will briefly discuss a novel, dynamics-based understanding of halo density profiles. The main focus of the talk will be ongoing efforts to build a practical framework to infer cluster properties and fundamental physics from a combination of multi-wavelength observables.
Supercomputing
Ares – Simulating Type Ia Supernovae on Heterogeneous HPC Architectures
Landon Dyken, Alexander Holas, Mark Ivan Ugalino, and 1 more author
In SC ’23: Proceedings of the International Conference for High Performance Computing, Networking, Storage and Analysis, Nov 2023
Type Ia Supernovae are highly luminous thermonuclear explosions of white dwarfs which serve as standardizable distance markers for investigating the accelerating expansion of our Universe. Most existing supernovae simulation codes are only designed to run on homogeneous CPU-only systems and do not take advantage of the increasing shift towards heterogeneous architectures in HPC. To address this, we present Ares, the first performance portable massively-parallel code for simulating thermonuclear burn fronts. By creating multi-physics modules using the Kokkos and Parthenon frameworks, we are able to scale supernovae simulations to distributed HPC clusters operating on any of CUDA, HIP, SYCL, HPX, OpenMP and serial backends. We evaluate our application by conducting weak and strong scaling studies on both CPU and GPU clusters, showing the efficiency of our method for a diverse set of targets.
AAS Conference
Turbulently driven deflagration to detonation transition in near-Chandrasekhar mass white dwarfs
Mark Ivan Ugalino, Chris Byrohl, Robert Fisher, and 2 more authors
In American Astronomical Society Meeting Abstracts #242, Jun 2023
Type Ia supernova events (SNe Ia) are highly luminous explosions used as standardizable candles that play a key role in measuring the equation of state of dark energy and the cosmological expansion of our universe. Despite their significance in cosmology and astrophysics, a complete understanding of the explosion physics that triggers these thermonuclear explosions has remained elusive until now. In this study, we analyze the turbulence statistics of thermonuclear flames in full 3D simulations of near-Chandrasekhar white dwarfs, varying the central density and ignition offset. Additionally, we discuss the implications of these measurements for the delay time between central ignition and detonation, as well as the general SNe Ia progenitor problem.
APS Conference
Turbulently-driven deflagration-to-detonation transition in near-Chandrasekhar mass white dwarfs
Mark Ivan Ugalino, Robert Fisher, Alexei Poludnenko, and 1 more author
Type Ia supernovae are luminous transients which enrich the interstellar medium with their nucleosynthetic products. They serve as crucial probes for observational cosmology, providing high-precision measurements of both the Hubble constant and cosmic acceleration. While multiple scenarios explaining type Ia supernovae have been proposed, a key physical process underpinning all channels is a detonation within the electron degenerate carbon-oxygen white dwarf interior. However, a first-principles understanding of how detonations are initiated in the turbulent conditions prevalent in SN Ia progenitors has remained elusive until now. In this work, we apply for the first time a laboratory-validated turbulently-driven deflagration-to-detonation (tDDT) mechanism to full 3D simulations of a near-Chandrasekhar mass carbon-oxygen white dwarf. We will present an analysis of the turbulently-driven flame propagation and characterize its local conditions at tDDT onset. We will also discuss the nucleosynthesis and the spectra that can be observed from tDDT-initiated type Ia supernovae events.
Theses
MSc Thesis
Turbulently driven deflagration-to-detonation transition in near-Chandrasekhar white dwarfs: a thesis in Physics
Type Ia supernova (SNe Ia) events are highly luminous explosions used as standardizable candles which play a key role in measuring the equation of state of dark energy and the cosmological expansion of our universe. Despite their key role in cosmology and astrophysics, a complete understanding of the explosion physics that triggers these thermonuclear explosions remains elusive until now. In this thesis, I present the first application of a novel laboratory-validated turbulently driven deflagration-to-detonation transition (tDDT) mechanism for thermonuclear flames to full-star three-dimensional hydrodynamical simulations of near-Chandrasekhar (near-M꜀ₕ) mass SNe Ia explosions. I discuss the role of turbulence-flame interactions in near-M꜀ₕ SNe Ia explosions, and the statistical characteristics of turbulently-driven flames in our simulations.
MSc Thesis
Dynamical friction effects on circular orbits immersed in a finite gaseous background
Models describing the dynamical friction experienced by a moving massive ob- ject involve an assumption that, throughout its trajectory, the background mediumis infinite; that is, the characteristic length of the background is much larger thanthe orbital radius. However, in most cases, astrophysical objects like planets andstars evolve in gaseous disks whose dimensions are finite. In this thesis, we derivedan expression for the hydrodynamical drag experienced by a point particle movingthrough a finite fluid background with cylindrical symmetry. We assume in thismethod that the particle has completed several orbits before measuring the force exerted.
BSc Thesis
Density perturbation induced by relativistic bodies in slightly-eccentric orbits
We consider a massive perturber moving along slightly-eccentric orbits through a collisional fluid in flat spacetime. We evaluate, via a frequency-domain calculation, the density perturbations induced by this massive perturber and reproduce the characteristic spiral wave structure previously computed for circular orbits with time-domain methods. This work serves as a precursor to a full calculation of the relativistic dynamical friction (DF) experienced by a perturber moving along a slightlyeccentric orbit. Our slightly-eccentric analysis is restricted by three conditions: (a) the perturbations are kept in linear order, (b) the weak-field region of the perturbed Schwarzschild spacetime is approximated as a perturbed Minkowski background, and (c) the fluid and the moving particle exist perpetually, ie. the perturbation was turned on long before the system was observed.