arXiv subjects

Dafa Wardana

Publications and source records attributed to Dafa Wardana.

3 recordsLinked to original sources

arXiv2026

Galactic Archaeology with the Subaru `\=Onohi`ula Prime Focus Spectrograph Strategic Program

The recently commissioned Subaru `\=Onohi`ula Prime Focus Spectrograph (PFS) will obtain spectra from nearly 2,400 fibers that cover 1.24 square degrees. The 360 night Subaru Strategic Program for PFS is dedicating approximately one-third of its allocation (130 nights) to study the structure and evolution of galaxies in the Local Group. This Galactic Archaeological survey has three pillars. (1) We will determine whether the mass density profiles of dwarf galaxies are consistent with cusps, as expected for cold dark matter, or cores, as expected from alternative dark matter theories or baryonic feedback. We will deduce the density profiles as a function of radius from modeling of the full line-of-sight velocity and abundance distributions for six dwarf galaxies. Our total sample will consist of 18,000 member stars to beyond the nominal tidal radius of each system. (2) From measurements of the [alpha/Fe] abundance ratio, we will learn the difference in assembly history of the two most massive galaxies in the Local Group: M31 and the Milky Way. We will observe 30,000 member stars over 45 square degrees of M31's halo and outer disk. (3) We will uncover how the most fragile (outer) part of the Milky Way responded to accretion events both in the distant past (such as Gaia-Sausage Enceladus) and in more recent history (such as the Sagittarius dwarf spheroidal galaxy). To support this study, PFS will provide velocities and metallicities--from which, in combination with photometry, we will deduce ages--for tens of thousands of main-sequence stars out to a Galactocentric distance of ~30 kpc.

astro-ph.GA↗

arXiv2026

Fuzzy Dark Matter and the Impact of Core--Halo Diversity on Its Particle Mass Constraints

We investigate how diversity in the core--halo mass relation and the inclusion of higher-order velocity moments affect constraints on the fuzzy dark matter particle mass ($m_\psi$) inferred from the internal kinematics of dwarf galaxies. Using stellar line-of-sight velocities and projected positions for eight Milky Way dwarf spheroidal galaxies, we model their dark matter halos as solitonic cores embedded within outer Navarro--Frenk--White envelopes. We apply both second- and fourth-order Jeans analyses to derive the posterior distribution of $m_\psi$. Our results show that there are two ranges of $m_\psi$ consistent with the observed kinematics: $\log_{10}(m_\psi/\mathrm{eV}) = -19.72^{+0.64}_{-0.56}$, and a narrower low-mass window $\log_{10}(m_\psi/\mathrm{eV}) = -21.81^{+0.39}_{-0.26}$, both within the 68\% credible intervals. The latter becomes prominent only when core--halo diversity is taken into account, which highlights the sensitivity of the inferred fuzzy dark matter particle mass constraints to our understanding of the core--halo relation. Future observations, providing larger stellar samples and more precise kinematic measurements, will be essential for clarifying the allowed parameter space of fuzzy dark matter.

astro-ph.GA↗

arXiv2025

Disentangling gamma-beta: the 4th-order velocity moments based on spherical Jeans analysis

Distinguishing a core and a cusp within dark matter halos is complexified by the existence of mass-anisotropy degeneracy, where various combinations of velocity anisotropy ($β$) and inner density slope ($γ$) yield similar observational signatures. We construct a dynamical model that incorporates the 4th-order velocity moments to alleviate this challenge. The inclusion of the 4th-order velocity moments enables stars' line-of-sight velocity distribution (LOSVD) to be flexible. This flexible LOSVD can cover from a thin-tailed to a heavy-tailed distribution that is inaccessible if only the 2nd-order moments are considered. We test the model on four mock galaxies having isotropic orbits, $β= 0$: two resembling dwarf spheroidal galaxies (dSphs) and two resembling ultra-faint dwarfs (UFDs) in terms of velocity dispersion. Each category includes one galaxy with a cuspy NFW profile and one with a cored density profile. Results show that a ratio of the global velocity dispersion to velocity error, $σ_{\rm los,global} / δv_{\rm los} \gtrsim 4$, is crucial to avoid systematic biases arising from the strong sensitivity of 4th-order moments to the LOSVD tails. In cases where this velocity ratio condition is met, our model reliably recovers $γ$ in dSph mock galaxies, with the true value recovered within $\sim 1σ$, and strongly excludes a cuspy NFW profile for the cored dSph mock galaxy. However, recovering the density profiles of UFDs remains challenging due to their intrinsically low velocity dispersions.

astro-ph.GA↗