arXiv subjects

Brad K. Gibson

Publications and source records attributed to Brad K. Gibson.

At least 19 recordsLinked to original sources

arXiv2025

Redshift Evolution of the Intrinsic Alignments of Early-Type Galaxies and Subhalos in the Horizon Run 5 Simulation

We investigate the redshift evolution of intrinsic alignments of the shapes of galaxies and subhalos with the large-scale structures of the universe using the cosmological hydrodynamic simulation, $\textit{Horizon Run 5}$. To this end, early-type galaxies are selected from the simulated galaxy catalogs based on stellar mass and kinematic morphology. The shapes of galaxies and subhalos are computed using the reduced inertia tensor derived from mass-weighted particle positions. We find that the misalignment between galaxies and their corresponding dark-matter subhalos decreases over time. We further analyze the two-point correlation between galaxy or subhalo shapes and the large-scale density field traced by their spatial distribution, and quantify the amplitude using the nonlinear alignment model across a wide redshift range from $z = 0.625$ to $z = 2.5$. We find that the intrinsic alignment amplitude, $A_{\rm NLA}$, of galaxies remains largely constant with redshift, whereas that of dark matter subhalos exhibits moderate redshift evolution, with a power-law slope that deviates from zero at a significance level exceeding $3σ$. Additionally, $A_{\rm NLA}$ is found to depend on both the stellar mass and kinematic morphology of galaxies. Notably, our results are broadly consistent with existing observational constraints. Our findings are in good agreement with previous results of other cosmological simulations.

astro-ph.CO↗

arXiv2025

Testing Lyman Alpha Emitters and Lyman-Break Galaxies as Tracers of Large-Scale Structures at High Redshifts

We test whether Lyman alpha emitters (LAEs) and Lyman-break galaxies (LBGs) can be good tracers of high-z large-scale structures, using the Horizon Run 5 cosmological hydrodynamical simulation. We identify LAEs using the Lyα emission line luminosity and its equivalent width, and LBGs using the broad-band magnitudes at z~2.4, 3.1, and 4.5. We first compare the spatial distributions of LAEs, LBGs, all galaxies, and dark matter around the filamentary structures defined by dark matter. The comparison shows that both LAEs and LBGs are more concentrated toward the dark matter filaments than dark matter. We also find an empirical fitting formula for the vertical density profile of filaments as a binomial power-law relation of the distance to the filaments. We then compare the spatial distributions of the samples around the filaments defined by themselves. LAEs and LBGs are again more concentrated toward their filaments than dark matter. We also find the overall consistency between filamentary structures defined by LAEs, LBGs, and dark matter, with the median spatial offsets that are smaller than the mean separation of the sample. These results support the idea that the LAEs and LBGs could be good tracers of large-scale structures of dark matter at high redshifts.

astro-ph.GA↗

arXiv2024

Emergence of the Galaxy Morphology-Star Formation Activity-Clustercentric Radius Relations in Galaxy Clusters

We investigate when and how the relations of galaxy morphology and star forming activity with clustercentric radius become evident in galaxy clusters. We identify 162 galaxy clusters with total mass $M_{\rm tot}^{\rm cl} > 5 \times 10^{13} {\rm M}_\odot$ at $z = 0.625$ in the Horizon Run 5 (HR5) cosmological hydrodynamical simulation and study how the properties of the galaxies with stellar mass $M_\ast > 5 \times 10^9 {\rm M}_\odot$ near the cluster main progenitors have evolved in the past. Galaxies are classified into disk, spheroid, and irregular morphological types according to the asymmetry and Sersic index of their stellar mass distribution. We also classify galaxies into active and passive ones depending on their specific star-formation rate. We find that the morphology-clustercentric radius relation (MRR) emerges at $z \simeq 1.8$ as the fraction of spheroidal types exceeds 50% in the central region ($d \lesssim 0.1 R_{200}$). Galaxies outside the central region remain disk-dominated. Numerous encounters between galaxies in the central region seem to be responsible for the morphology transformation from disks to spheroids. We also find that the star formation activity-clustercentric radius relation emerges at an epoch different from that of MRR. At $z\simeq0.8$, passive galaxies start to dominate the intermediate radius region ($0.1\lesssim d/R_{200} \lesssim0.3$) and this "quenching region" grows inward and outward thereafter. The region dominated by early-type galaxies (spheroids and passive disks) first appears at the central region at $z\simeq 1.8$, expands rapidly to larger radii as the population of passive disks grows in the intermediate radii, and clusters are dominated by early types after $z\simeq 0.8$.

astro-ph.GA↗

arXiv2024

Star-formation Properties of z ~ 1 Galaxy Clusters and Groups from Horizon Run 5

Quiescent galaxies are predominantly observed in local galaxy clusters. However, the fraction of quiescent galaxies in high-redshift clusters significantly varies among different clusters. In this study, we present the results of an analysis of the star formation (SF) properties of $z \sim 0.87$ clusters and groups from a cosmological hydrodynamical simulation Horizon Run 5. We investigate the correlation between the quiescent galaxy fraction (QF) of these model clusters/groups and their various internal or external properties. We find that halo mass is one of the most important characteristics as higher mass clusters and groups have higher QFs. We also find that other properties such as stellar-mass ratio and Friends-of-Friends fraction, which measures the proportion of the area around a cluster occupied by dense structures, may mildly affect the QFs of clusters and groups. This may indicate that the evolutionary history as well as the large-scale environment of clusters and groups also play a certain role in determining the SF status of high-redshift galaxy clusters and groups.

astro-ph.GA↗

arXiv2024

Predictions for CO emission and the CO-to-H$_2$ conversion factor in galaxy simulations with non-equilibrium chemistry

Our ability to trace the star-forming molecular gas is important to our understanding of the Universe. We can trace this gas using CO emission, converting the observed CO intensity into the H$_2$ gas mass of the region using the CO-to-H$_2$ conversion factor (Xco). In this paper, we use simulations to study the conversion factor and the molecular gas within galaxies. We analysed a suite of simulations of isolated disc galaxies, ranging from dwarfs to Milky Way-mass galaxies, that were run using the FIRE-2 subgrid models coupled to the CHIMES non-equilibrium chemistry solver. We use the non-equilibrium abundances from the simulations, and we also compare to results using abundances assuming equilibrium, which we calculate from the simulation in post-processing. Our non-equilibrium simulations are able to reproduce the relation between CO and H$_2$ column densities, and the relation between Xco and metallicity, seen within observations of the Milky Way. We also compare to the xCOLD GASS survey, and find agreement with their data to our predicted CO luminosities at fixed star formation rate. We also find the multivariate function used by xCOLD GASS overpredicts the H$_2$ mass for our simulations, motivating us to suggest an alternative multivariate function of our fitting, though we caution that this fitting is uncertain due to the limited range of galaxy conditions covered by our simulations. We also find that the non-equilibrium chemistry has little effect on the conversion factor (<5\%) for our high-mass galaxies, though still affects the H$_2$ mass and Lco by $\approx$25\%.

astro-ph.GA↗

arXiv2024

The Environmental Dependence of the Stellar Mass - Gas Metallicity Relation in Horizon Run 5

Metallicity offers a unique window into the baryonic history of the cosmos, being instrumental in probing evolutionary processes in galaxies between different cosmic environments. We aim to quantify the contribution of these environments to the scatter in the mass-metallicity relation (MZR) of galaxies. By analysing the galaxy distribution within the cosmic skeleton of the Horizon Run 5 cosmological hydrodynamical simulation at redshift $z = 0.625$, computed using a careful calibration of the T-ReX filament finder, we identify galaxies within three main environments: nodes, filaments and voids. We also classify galaxies based on the dynamical state of the clusters and the length of the filaments in which they reside. We find that the cosmic environment significantly contributes to the scatter in the MZR; in particular, both the gas metallicity and its average relative standard deviation increase when considering denser large-scale environments. The difference in the average metallicity between galaxies within relaxed and unrelaxed clusters is $\approx 0.1 \text{ dex}$, with both populations displaying positive residuals, $δZ_{g}$, from the averaged MZR. Moreover, the difference in metallicity between node and void galaxies accounts for $\approx 0.14 \, \text{dex}$ in the scatter of the MZR at stellar mass $M_{\star} \approx 10^{9.35}\,\text{M}_{\odot}$. Finally, both the average [O/Fe] in the gas and the galaxy gas fraction decrease when moving to higher large-scale densities in the simulation, suggesting that the cores of cosmic environments host, on average, older and more massive galaxies, whose enrichment is affected by a larger number of Type Ia Supernova events.

astro-ph.GA↗

arXiv2024

Modelling Triatomic Biosignatures: Ozone and Isotopomers

In this work we present a new approach to produce spectroscopic constants and model first-principles synthetic spectra for all molecules of astrophysical interest. We have generalized our previous diatomic molecule simulation framework, employing Transition-Optimised Shifted Hermite (TOSH) theory, thereby enabling the modelling of polyatomic rotational constants for molecules with three or more atoms. These capabilities, are now provided by our new code Epimetheus. As a first validation of our approach, we confront our predictions and assess their accuracy against the well-studied triatomic molecule, ozone 666 ($^{16}$O$_3$), in addition to eight of its potential isotopomers: ozone 668 ($^{16}$O$^{16}$O$^{18}$O), 686 ($^{16}$O$^{18}$O$^{16}$O), 667 ($^{16}$O$^{16}$O$^{17}$O), 676 ($^{16}$O$^{17}$O$^{16}$O), 688 ($^{16}$O$^{18}$O$^{18}$O), 868 ($^{18}$O$^{16}$O$^{18}$O), 888 ($^{18}$O$_3$), and 777 ($^{17}$O$_3$). We then assess the accuracy of these rotational constants using the Epimetheus data in our code Pandora, and generate synthetic molecular spectra. The ozone spectra presented here are purely infrared and not Raman. Epimetheus builds upon the work from our previous code Prometheus, which used the TOSH theory to account for anharmonicity for the fundamental $ν=0 \rightarrow ν=1$ band, going further to now account for triatomic molecules. This is combined with thermal profile modeling for the rotational transitions. We have found that this extended method performs promisingly, typically approximating the spectroscopic constants and spectra well. Some issues do arise depending on the symmetry group of the ozone isotopomer. In general, we show that Epimetheus can provide the data to produce appreciable molecular spectra, to help drive future high-resolution studies.

physics.chem-ph↗

arXiv2024

Spatial Distribution of Intracluster Light versus Dark Matter in Horizon Run 5

One intriguing approach for studying the dynamical evolution of galaxy clusters is to compare the spatial distributions among various components, such as dark matter, member galaxies, gas, and intracluster light (ICL). Utilizing the recently introduced Weighted Overlap Coefficient (WOC) \citep{2022ApJS..261...28Y}, we analyze the spatial distributions of components within 174 galaxy clusters ($M_{\rm tot}> 5 \times 10^{13} M_{\odot}$, $z=0.625$) at varying dynamical states in the cosmological hydrodynamical simulation Horizon Run 5. We observe that the distributions of gas and the combination of ICL with the brightest cluster galaxy (BCG) closely resembles the dark matter distribution, particularly in more relaxed clusters, characterized by the half-mass epoch. The similarity in spatial distribution between dark matter and BCG+ICL mimics the changes in the dynamical state of clusters during a major merger. Notably, at redshifts $>$ 1, BCG+ICL traced dark matter more accurately than the gas. Additionally, we examined the one-dimensional radial profiles of each component, which show that the BCG+ICL is a sensitive component revealing the dynamical state of clusters. We propose a new method that can approximately recover the dark matter profile by scaling the BCG+ICL radial profile. Furthermore, we find a recipe for tracing dark matter in unrelaxed clusters by including the most massive satellite galaxies together with BCG+ICL distribution. Combining the BCG+ICL and the gas distribution enhances the dark matter tracing ability. Our results imply that the BCG+ICL distribution is an effective tracer for the dark matter distribution, and the similarity of spatial distribution may be a useful probe of the dynamical state of a cluster.

astro-ph.CO↗

arXiv2023

Identification of Galaxy Protoclusters Based on the Spherical Top-hat Collapse Theory

We propose a new method for finding galaxy protoclusters that is motivated by structure formation theory and also directly applicable to observations. We adopt the conventional definition that a protocluster is a galaxy group whose virial mass $M_{\rm vir} < M_{\rm cl}$ at its epoch, where $M_{\rm cl}=10^{14}\,M_{\odot}$, but would exceed that limit when it evolves to $z=0$. We use the critical overdensity for complete collapse at $z = 0$ predicted by the spherical top-hat collapse model to find the radius and total mass of the regions that would collapse at $z=0$. If the mass of a region centered at a massive galaxy exceeds $M_{\rm cl}$, the galaxy is at the center of a protocluster. We define the outer boundary of protocluster as the zero-velocity surface at the turnaround radius so that the member galaxies are those sharing the same protocluster environment and showing some conformity in physical properties. We use the cosmological hydrodynamical simulation Horizon Run 5 (HR5) to calibrate this prescription and demonstrate its performance. We find that the protocluster identification method suggested in this study is quite successful. Its application to the high-redshift HR5 galaxies shows a tight correlation between the mass within the protocluster regions identified according to the spherical collapse model and the final mass to be found within the clusters at $z=0$, meaning that the regions can be regarded as the bona fide protoclusters with high reliability. We also confirm that the redshift-space distortion does not significantly affect the performance of the protocluster identification scheme.

astro-ph.GA↗

arXiv2023

The Horizon Run 5 Cosmological Hydrodynamic Simulation: Probing Galaxy Formation from Kilo- to Giga-parsec Scales

Horizon Run 5 (HR5) is a cosmological hydrodynamical simulation which captures the properties of the Universe on a Gpc scale while achieving a resolution of 1kpc. Inside the simulation box we zoom-in on a high-resolution cuboid region with a volume of $1049\times119\times127\,{\rm cMpc}^3$.The sub-grid physics chosen to model galaxy formation includes radiative heating/cooling, UV background, star formation, supernova feedback, chemical evolution tracking the enrichment of oxygen and iron, the growth of supermassive black holes and feedback from active galactic nuclei (AGN) in the form of a dual jet-heating mode. For this simulation we implemented a hybrid MPI-OMP version of RAMSES, specifically targeted for modern many-core many thread parallel architectures. In addition to the traditional simulation snapshots, light-cone data was generated on the fly. For the post-processing, we extended the Friends-of-Friend (FoF) algorithm and developed a new galaxy finder PGalF to analyse the outputs of HR5. The simulation successfully reproduces observations, such as the cosmic star formation history and connectivity of galaxy distribution, We identify cosmological structures at a wide range of scales, from filaments with a length of several cMpc, to voids with a radius of ~100 cMpc. The simulation also indicates that hydrodynamical effects on small scales impact galaxy clustering up to very large scales near and beyond the baryonic acoustic oscillation (BAO) scale. Hence, caution should be taken when using that scale as a cosmic standard ruler: one needs to carefully understand the corresponding biases. The simulation is expected to be an invaluable asset for the interpretation of upcoming deep surveys of the Universe.

astro-ph.GA↗

arXiv2023

On the Effects of Local Environment on Active Galactic Nucleus (AGN) in the Horizon Run 5 Simulation

We use the Horizon Run 5 cosmological simulation to study the effect of galaxy intrinsic properties and the local environment on AGNs characterized by their threshold of the accretion rate. We select galaxies in the stellar mass range $10^{9.5} \le M^{}{*}/M^{}{\odot} \le 10^{10.5}$ in the snapshot at redshift $z$=0.625. Among various intrinsic properties, we find that the star formation rate of the host galaxy is most correlated to the AGN activity. To quantify the environment, we use background galaxy number density (large-scale environment) and distance and morphological type of the nearest neighbors (small-scale environment), and study their relative effects on the AGN properties. We find that, compared to the background density, the nearest neighbor environment is the dominant quantity determining the bolometric luminosity, star formation rate, and kinematic properties of AGNs and better dictates the gas mass of the host galaxy. We show that the cold gas content in the host galaxies is crucial in triggering AGN activity. However, when the nearest neighbor environment effects start to act at the neighbor distance of less than about half the virial radius of the neighbor, the neighbor environmental effects are the most dominant factor for quasar activity.

astro-ph.GA↗

arXiv2023

The chemical evolution of the solar neighbourhood for planet-hosting stars

Theoretical physical-chemical models for the formation of planetary systems depend on data quality for the Sun's composition, that of stars in the solar neighbourhood, and of the estimated "pristine" compositions for stellar systems. The effective scatter and the observational uncertainties of elements within a few hundred parsecs from the Sun, even for the most abundant metals like carbon, oxygen and silicon, are still controversial. Here we analyse the stellar production and the chemical evolution of key elements that underpin the formation of rocky (C, O, Mg, Si) and gas/ice giant planets (C, N, O, S). We calculate 198 galactic chemical evolution (GCE) models of the solar neighbourhood to analyse the impact of different sets of stellar yields, of the upper mass limit for massive stars contributing to GCE ($M_{\rm up}$) and of supernovae from massive-star progenitors which do not eject the bulk of the iron-peak elements (faint supernovae). Even considering the GCE variation produced via different sets of stellar yields, the observed dispersion of elements reported for stars in the Milky Way disk is not reproduced. Among others, the observed range of super-solar [Mg/Si] ratios, sub-solar [S/N], and the dispersion of up to 0.5 dex for [S/Si] challenge our models. The impact of varying $M_{\rm up}$ depends on the adopted supernova yields. Thus, observations do not provide a constraint on the M$_{\rm up}$ parametrization. When including the impact of faint supernova models in GCE calculations, elemental ratios vary by up to 0.1-0.2 dex in the Milky Way disk; this modification better reproduces observations.

astro-ph.GA↗

arXiv2022

Chemical Evolution of Fluorine in the Milky Way

Fluorine has many different potential sites and channels of production, making narrowing down a dominant site of fluorine production particularly challenging. In this work, we investigate which sources are the dominant contributors to the galactic fluorine by comparing chemical evolution models to observations of fluorine abundances in Milky Way stars covering a metallicity range -2$<$[Fe/H]$<$0.4 and upper limits in the range -3.4$<$[Fe/H]$<$-2.3. In our models, we use a variety of stellar yield sets in order to explore the impact of varying both AGB and massive star yields on the chemical evolution of fluorine. In particular, we investigate different prescriptions for initial rotational velocity in massive stars as well as a metallicity dependent mix of rotational velocities. We find that the observed [F/O] and [F/Fe] abundance ratios at low metallicity and the increasing trend of [F/Ba] at [Fe/H]$\gtrsim$-1 can only be reproduced by chemical evolution models assuming, at all metallicities, a contribution from rapidly rotating massive stars with initial rotational velocities as high as 300km s$^{-1}$. A mix of rotational velocities may provide a more physical solution than the sole use of massive stars with $v_{\text{rot}}$=300$\text{km s}^{-1}$, which are predicted to overestimate the fluorine and average s-process elemental abundances at [Fe/H]$\gtrsim$-1. The contribution from AGB stars is predicted to start at [Fe/H]$\approx$-1 and becomes increasingly important at high metallicity, being strictly coupled to the evolution of the nitrogen abundance. Finally, by using modern yield sets, we investigate the fluorine abundances of Wolf-Rayet winds, ruling them out as dominant contributors to the galactic fluorine.

astro-ph.GA↗

arXiv2022

Formation and Morphology of the First Galaxies in the Cosmic Morning

We investigate the formation and morphological evolution of the first galaxies in the cosmic morning ($10 \gtrsim z \gtrsim 4$) using the Horizon Run 5 (HR5) simulation. For galaxies above the stellar mass $M_{\star, {\rm min}} = 2\times 10^9\,M_{\odot}$, we classify them into disk, spheroid, and irregular types according to their asymmetry and stellar mass morphology. We find that about 2/3 of the galaxies have a Sérsic index $< 1.5$, reflecting the dominance of disk-type morphology in the cosmic morning. The rest are evenly distributed as incidental and transient irregulars or spheroids. These fractions are roughly independent of redshift and stellar mass up to $\sim10^{10}\,M_{\odot}$. Almost all the first galaxies with $M_{\star}> M_{\star, {\rm min}}$ at $z>4$ form at initial peaks of the matter density field. Large-scale structures in the universe emerge and grow like cosmic rhizomes as the underlying matter density fluctuations grow and form associations of galaxies in rare overdense regions and the realm of the galactic world is stretched into relatively lower-density regions along evolving filaments. The cosmic web of galaxies forms at lower redshifts when most rhizomes globally percolate. The primordial angular momentum produced by the induced tidal torques on protogalactic regions is correlated with the internal kinematics of galaxies and tightly aligned with the angular momentum of the total galaxy mass. The large-scale tidal field imprinted in the initial conditions seems responsible for the dominance of disk morphology, and for the tendency of galaxies to re-acquire a disk post-distortion.

astro-ph.GA↗

arXiv2022

Radioactive nuclei in the early Solar System: analysis of the 15 isotopes produced by core-collapse supernovae

Short-lived radioactive isotopes (SLRs) with half-lives between 0.1 to 100 Myr can be used to probe the origin of the Solar System. In this work, we examine the core-collapse supernovae production of the 15 SLRs produced: $^{26}$Al, $^{36}$Cl, $^{41}$Ca, $^{53}$Mn, $^{60}$Fe, $^{92}$Nb, $^{97}$Tc, $^{98}$Tc, $^{107}$Pd, $^{126}$Sn, $^{129}$I, $^{135}$Cs, $^{146}$Sm, $^{182}$Hf, and $^{205}$Pb. We probe the impact of the uncertainties of the core-collapse explosion mechanism by examining a collection of 62 core-collapse models with initial masses of 15, 20, and 25M$_{\odot}$, explosion energies between 3.4$\times$10$^{50}$ and 1.8$\times$10$^{52}$ ergs and compact remnant masses between 1.5M$_{\odot}$and 4.89M$_{\odot}$. We identify the impact of both explosion energy and remnant mass on the final yields of the SLRs. Isotopes produced within the innermost regions of the star, such as $^{92}$Nb and $^{97}$Tc, are the most affected by the remnant mass, $^{92}$Nb varying by five orders of magnitude. Isotopes synthesised primarily in explosive C-burning and explosive He-burning, such as $^{60}$Fe, are most affected by explosion energies. $^{60}$Fe increases by two orders of magnitude from the lowest to the highest explosion energy in the 15M$_{\odot}$model. The final yield of each examined SLR is used to compare to literature models.

astro-ph.SR↗

arXiv2021

A Large-scale Approach to Modelling Molecular Biosignatures: The Diatomics

This work presents the first steps to modelling synthetic rovibrational spectra for all molecules of astrophysical interest using a new approach implemented in the Prometheus code. The goal is to create a new comprehensive source of first-principles molecular spectra, thus bridging the gap for missing data to help drive future high-resolution studies. Our primary application domain is for molecules identified as signatures of life in planetary atmospheres (biosignatures), but our approach is general and can be applied to other systems. In this work we evaluate the accuracy of our method by studying four diatomic molecules H$_2$, O$_2$, N$_2$ and CO, all of which have well-known spectra. Prometheus uses the Transition-Optimised Shifted Hermite (TOSH) theory to account for anharmonicity for the fundamental $ν=0 \rightarrow ν=1$ band, along with thermal profile modeling for the rotational transitions. To this end, we expand TOSH theory to enable the modeling of rotational constants. We show that our simple model achieves results that are a better approximation of the real spectra than those produced through a harmonic approach. We compare our results with high-resolution HITRAN and ExoMol spectral data. We find that modelling accuracy tends to diminish for rovibrational transition away from the band origin, thus highlighting the need for the theory to be further adapted.

physics.chem-ph↗

arXiv2021

Project ThaiPASS: International Outreach Blending Astronomy and Python

$\textit{Thailand-UK Python+Astronomy Summer School}$ (ThaiPASS), a collaborative project comprising UK and Thai institutions and assess its impact and possible application to schools in the United Kingdom. Since its inception in 2018, the annual ThaiPASS have trained around 60 Thai high-school students in basic data handling skills using Python in the context of various astronomy topics, using current research from the teaching team. Our impact assessment of the 5 day summer schools show an overwhelmingly positive response from students in both years, with over $80\%$ of students scoring the activities above average in all activities but one. We use this data to suggest possible future improvements. We also discuss how ThaiPASS may inspire further outreach and engagement activities within the UK and beyond.

physics.ed-ph↗

arXiv2020

The $R$-Process Alliance: Fourth Data Release from the Search for $r$-Process-Enhanced Stars in the Galactic Halo

This compilation is the fourth data release from the $R$-Process Alliance (RPA) search for $r$-process-enhanced stars, and the second release based on "snapshot" high-resolution ($R \sim 30,000$) spectra collected with the du Pont 2.5m Telescope. In this data release, we propose a new delineation between the $r$-I and $r$-II stellar classes at $\mathrm{[Eu/Fe]} = +0.7$, instead of the empirically chosen $\mathrm{[Eu/Fe]} = +1.0$ level previously in use, based on statistical tests of the complete set of RPA data released to date. We also statistically justify the minimum level of [Eu/Fe] for definition of the $r$-I stars, [Eu/Fe] $> +0.3$. Redefining the separation between $r$-I and $r$-II stars will aid in analysis of the possible progenitors of these two classes of stars and whether these signatures arise from separate astrophysical sources at all. Applying this redefinition to previous RPA data, the number of identified $r$-II and $r$-I stars changes to 51 and 121, respectively, from the initial set of data releases published thus far. In this data release, we identify 21 new $r$-II, 111 new $r$-I (plus three re-identified), and 7 new (plus one re-identified) limited-$r$ stars out of a total of 232 target stars, resulting in a total sample of 72 new $r$-II stars, 232 new $r$-I stars, and 42 new limited-$r$ stars identified by the RPA to date.

astro-ph.SR↗