arXiv subjects

Gray Thoron

Publications and source records attributed to Gray Thoron.

4 recordsLinked to original sources

arXiv2026

Simulations agree: the Milky Way's satellites are disrupting

Recent analyses of simulated Milky Way-mass galaxies have highlighted the prevalence of satellites undergoing tidal disruption. However, these have focused on single hydrodynamical codes with a number of limitations, making it unclear how generic this result is. We compare satellite disruption in four models: two cosmological hydrodynamical simulations (Auriga and FIRE), cosmological $N$-body simulations with stellar particle tagging (Aquarius), and a semi-analytic model with varying host disk properties (SatGen). For all systems, we compute the fraction of stellar mass retained by the progenitor ($f_\text{bound}$) at the present day. We find a remarkable agreement between FIRE, Aquarius, and SatGen; all predict that $\sim$20 to 30 per cent of classical-mass satellites have $f_\text{bound} < 0.9$ ($\sim$5 to 10 per cent have $f_\text{bound} < 0.5$). Satellites in Auriga experience substantially more mass loss than other simulations, which we attribute to their massive central galaxies and large satellite sizes prior to infall. In the ultra-faint regime captured by Aquarius and SatGen, disruption rates are comparable to or exceeding those for classical satellites. The ubiquity of mass loss across models presents both an exciting opportunity (a plethora of stellar streams awaiting discovery) and a nuisance (for theorists using satellite counts to constrain dark matter).

astro-ph.GA↗

arXiv2026

Hidden Disruption in Milky Way-like Satellite Galaxy Populations

Determining whether a satellite galaxy is tidally disrupting from photometric observations alone remains a fundamental challenge in near-field cosmology. Cosmological simulations of Milky Way-mass galaxies predict that satellite populations should be highly disrupted, yet the observed Milky Way satellite population appears largely intact. Understanding this tension requires either uncovering disruption that has gone undetected in Milky Way satellites, or identifying limitations in the simulations themselves. We use the Auriga suite of cosmological simulations to evaluate several commonly used indicators of disruption. We find that, in the simulated satellite population, the shape, size, and proper motion alignment of a satellite's bound component are unreliable indicators of its present-day disruption state despite their widespread use in the literature. In contrast, the extended stellar distribution, specifically the ratio of stellar mass between $3r_{1/2}$ and $10r_{1/2}$ to that within $r_{1/2}$, is strongly correlated with disruption. We introduce the extended mass ratio $μ_{\rm EMR}$ as a metric for comparing extended stellar distributions across satellites of varying masses and exploring their connection to disruption in Milky Way observations. Applying this metric to a sample of Milky Way satellites with measured extended stellar distributions, we find that many are consistent with significant ongoing disruption, even among systems traditionally classified as intact. These results suggest that tidal disruption may be substantially more widespread in the observed Milky Way satellite population than currently recognized, and establish extended stellar distributions as a promising new tool for uncovering this hidden disruption.

astro-ph.GA↗

arXiv2025

Crowded Field Photometry with Rubin: Exploring 47 Tucanae with Data Preview 1

We analyze imaging from Data Preview 1 of the Vera C. Rubin Observatory to explore the performance of early LSST pipelines in the 47 Tucanae field. The coadd-\texttt{object} catalog demonstrates the depth and precision possible with Rubin, recovering well-defined color magnitude diagrams for 47 Tuc Small Magellanic Cloud. Unfortunately, the existing pipelines fail to recover sources within $\sim$28 pc of the cluster center, due to the extreme source density. Using Rubin's forced photometry on stars identified via Difference Imaging, we can recover sources down to $\sim$14 pc from the cluster center, and find 14744 potential cluster members with this extended dataset. While this forced photometry has significant systematics, our analysis showcases the potential for detailed structural studies of crowded fields with the Rubin Observatory.

astro-ph.GA↗

arXiv2023

Examining the Self-Interaction of Dark Matter through Central Cluster Galaxy Offsets

While collisionless cold dark matter models have been largely successful in explaining a wide range of observational data, some tensions still exist, and it remains possible that dark matter possesses a non-negligible level of self interactions. In this paper, we investigate a possible observable consequence of self-interacting dark matter: offsets between the central galaxy and the center of mass of its parent halo. We examine 23 relaxed galaxy clusters in a redshift range of 0.1 to 0.3 drawn from clusters in the Dark Energy Survey and the Sloan Digital Sky Survey which have archival Chandra X-ray data of sufficient depth for center and relaxation determination. We find that most clusters in our sample show non-zero offsets between the X-ray center, taken to be the centroid within the cluster core, and the central galaxy position. All of the measured offsets are larger, typically by an order of magnitude, than the uncertainty in the X-ray position due to Poisson noise. In all but six clusters, the measured offsets are also larger than the estimated, combined astrometric uncertainties in the X-ray and optical positions. A more conservative cut on concentration to select relaxed clusters marginally reduces but does not eliminate the observed offset. With our more conservative sample, we find an estimated mean X-ray to central galaxy offset of $μ= 5.5 \pm 1.0$ kpc. Comparing to recent simulations, this distribution of offsets is consistent with some level of dark matter self interaction, though further simulation work is needed to place constraints.

astro-ph.CO↗