Anna Frebel
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View article: Decoding the Galactic Twirl: The Downfall of Milky Way–Mass Galaxy Rotation Curves in the FIRE Simulations
Decoding the Galactic Twirl: The Downfall of Milky Way–Mass Galaxy Rotation Curves in the FIRE Simulations Open
Recent measurements of the Milky Way rotation curve found a sharp decline at around 15–20 kpc from the center of the Galaxy, suggesting that the Galactic dark matter halo is much less massive than predicted by other dynamical tracers. To a…
View article: A Bimodal Metallicity Distribution Function in the Ultra-Faint Dwarf Galaxy Reticulum II
A Bimodal Metallicity Distribution Function in the Ultra-Faint Dwarf Galaxy Reticulum II Open
Star formation in ultra-faint dwarf galaxies (UFDs, ) is suppressed by reionization, but may not be completely quenched. The metallicity distribution function (MDF) of stars in ultra-faint dwarf galaxies could show these signat…
View article: <scp>Aeos</scp>: The Impact of Population III Initial Mass Function and Star-by-star Models in Galaxy Simulations
<span>Aeos</span>: The Impact of Population III Initial Mass Function and Star-by-star Models in Galaxy Simulations Open
We explore the effect of variations in the Population III initial mass function (IMF) and star-by-star feedback on early galaxy formation and evolution using the A eos simulations. We compare simulations with two different Population III I…
View article: Aeos is Mixing it Up: The (In)homogeneity of Metal Mixing Following Population III Star Formation
Aeos is Mixing it Up: The (In)homogeneity of Metal Mixing Following Population III Star Formation Open
Stellar surface abundances are records of the state of the gas from which stars formed, and thus trace how individual elements have mixed into the surrounding medium following their ejection from stars. In this work, we test the common ass…
View article: Deciphering the origins of the elements through galactic archeology
Deciphering the origins of the elements through galactic archeology Open
Low-metallicity stars preserve the signatures of the first stellar nucleosynthesis events in the Galaxy, as their surface abundances reflect the composition of the interstellar medium from the time when they were born. Aside from primordia…
View article: The <i>R</i>-process Alliance: Enrichment of <i>r</i>-process Elements in a Simulated Milky Way–like Galaxy
The <i>R</i>-process Alliance: Enrichment of <i>r</i>-process Elements in a Simulated Milky Way–like Galaxy Open
We study the formation of stars with varying amounts of heavy elements synthesized by the rapid neutron-capture process ( r -process) based on our detailed cosmological zoom-in simulation of a Milky Way–like galaxy with an N -body/smoothed…
View article: Discovery of an [Fe/H] ∼ −4.8 Star in Gaia XP Spectra<sup>*</sup>
Discovery of an [Fe/H] ∼ −4.8 Star in Gaia XP Spectra<sup>*</sup> Open
We report on the discovery of GDR3_526285 (Gaia DR3 Source ID 5262850721755411072), a star with [Fe/H] = −4.82 ± 0.25 and one of the lowest metal (atomic number > 2) mass fractions ever found ( Z GDR3 _ 526585 ≲ 1.0 × 10 −6 ). We first ide…
View article: GLIMPSE: An Ultrafaint ≃10<sup>5</sup> <i>M</i> <sub>⊙</sub> Pop III Galaxy Candidate and First Constraints on the Pop III UV Luminosity Function at <i>z</i> ≃ 6–7
GLIMPSE: An Ultrafaint ≃10<sup>5</sup> <i>M</i> <sub>⊙</sub> Pop III Galaxy Candidate and First Constraints on the Pop III UV Luminosity Function at <i>z</i> ≃ 6–7 Open
Detecting the first generation of stars, Population III (Pop III), has been a long-standing goal in astrophysics, yet they remain elusive even in the JWST era. Here we present a novel NIRCam-based selection method for Pop III galaxies, and…
View article: A Gravitational-wave-detectable Candidate Type Ia Supernova Progenitor
A Gravitational-wave-detectable Candidate Type Ia Supernova Progenitor Open
Type Ia supernovae (SNe Ia), critical for studying cosmic expansion, arise from thermonuclear explosions of white dwarfs, but their precise progenitor pathways remain unclear. Growing evidence supports the “double-degenerate scenario,” whe…
View article: Probing Abundance Variations Among Multiple Stellar Populations in the Metal-poor Globular Cluster NGC 2298 Using Gemini-South/GHOST*
Probing Abundance Variations Among Multiple Stellar Populations in the Metal-poor Globular Cluster NGC 2298 Using Gemini-South/GHOST* Open
Studying the abundances in metal-poor globular clusters is crucial for understanding the formation of the Galaxy and the nucleosynthesis processes in the early Universe. We observed 13 red-giant stars from the metal-poor globular cluster N…
View article: Probing Abundance Variations among Multiple Stellar Populations in the Metal-Poor Globular Cluster NGC 2298 using Gemini-South/GHOST
Probing Abundance Variations among Multiple Stellar Populations in the Metal-Poor Globular Cluster NGC 2298 using Gemini-South/GHOST Open
Studying the abundances in metal-poor globular clusters is crucial for understanding the formation of the Galaxy and the nucleosynthesis processes in the early Universe. We observed 13 red giant stars from the metal-poor globular cluster N…
View article: Early <i>r</i>-process Enrichment and Hierarchical Assembly Across the Sagittarius Dwarf Galaxy*
Early <i>r</i>-process Enrichment and Hierarchical Assembly Across the Sagittarius Dwarf Galaxy* Open
Dwarf galaxies like Sagittarius (Sgr) provide a unique window into the early stages of galactic chemical evolution, particularly through their metal-poor stars. By studying the chemical abundances of stars in the Sgr core and tidal streams…
View article: AEOS: Transport of Metals from Minihalos following Population III Stellar Feedback
AEOS: Transport of Metals from Minihalos following Population III Stellar Feedback Open
We investigate how stellar feedback from the first stars (Population III) distributes metals through the interstellar and intergalactic medium using the star-by-star cosmological hydrodynamics simulation, A eos . We find that energy inject…
View article: AEOS: Star-by-star Cosmological Simulations of Early Chemical Enrichment and Galaxy Formation
AEOS: Star-by-star Cosmological Simulations of Early Chemical Enrichment and Galaxy Formation Open
The A eos project introduces a series of high-resolution cosmological simulations that model star-by-star chemical enrichment and galaxy formation in the early Universe, achieving 1 pc resolution. These simulations capture the complexities…
View article: Early r-process Enrichment and Hierarchical Assembly Across the Sagittarius Dwarf Galaxy
Early r-process Enrichment and Hierarchical Assembly Across the Sagittarius Dwarf Galaxy Open
Dwarf galaxies like Sagittarius (Sgr) provide a unique window into the early stages of galactic chemical evolution, particularly through their metal-poor stars. By studying the chemical abundances of stars in the Sgr core and tidal streams…
View article: GLIMPSE: An ultra-faint $\simeq$ 10$^{5}$ $M_{\odot}$ Pop III Galaxy Candidate and First Constraints on the Pop III UV Luminosity Function at $z\simeq6-7$
GLIMPSE: An ultra-faint $\simeq$ 10$^{5}$ $M_{\odot}$ Pop III Galaxy Candidate and First Constraints on the Pop III UV Luminosity Function at $z\simeq6-7$ Open
Detecting the first generation of stars, Population III (PopIII), has been a long-standing goal in astrophysics, yet they remain elusive even in the JWST era. Here we present a novel NIRCam-based selection method for PopIII galaxies, and c…
View article: A gravitational wave detectable candidate Type Ia supernova progenitor
A gravitational wave detectable candidate Type Ia supernova progenitor Open
Type Ia supernovae, critical for studying cosmic expansion, arise from thermonuclear explosions of white dwarfs, but their precise progenitor pathways remain unclear. Growing evidence supports the ``double-degenerate'' scenario, where two …
View article: Metal-Poor Stars in the Milky Way System
Metal-Poor Stars in the Milky Way System Open
Ancient, long-lived stars remain present in all components of our home galaxy, the Milky Way. Born a few hundred million after the Big Bang and during a time that marked the very beginning of the chemical evolution, these stars display ver…
View article: Aeos: Transport of Metals from Minihalos following Population III Stellar Feedback
Aeos: Transport of Metals from Minihalos following Population III Stellar Feedback Open
We investigate how stellar feedback from the first stars (Population III) distributes metals through the interstellar and intergalactic medium using the star-by-star cosmological hydrodynamics simulation, Aeos. We find that energy injected…
View article: AEOS: Star-by-Star Cosmological Simulations of Early Chemical Enrichment and Galaxy Formation
AEOS: Star-by-Star Cosmological Simulations of Early Chemical Enrichment and Galaxy Formation Open
The AEOS project introduces a series of high-resolution cosmological simulations that model star-by-star chemical enrichment and galaxy formation in the early Universe, achieving 1 pc resolution. These simulations capture the complexities …
View article: The $R$-Process Alliance: Enrichment of $r$-process Elements in a Simulated Milky Way-like Galaxy
The $R$-Process Alliance: Enrichment of $r$-process Elements in a Simulated Milky Way-like Galaxy Open
We study the formation of stars with varying amounts of heavy elements synthesized by the rapid neutron-capture process ($r$-process) based on our detailed cosmological zoom-in simulation of a Milky Way-like galaxy with an $N$-body/smoothe…
View article: All the Little Things in Abell 2744: $>$1000 Gravitationally Lensed Dwarf Galaxies at $z=0-9$ from JWST NIRCam Grism Spectroscopy
All the Little Things in Abell 2744: $>$1000 Gravitationally Lensed Dwarf Galaxies at $z=0-9$ from JWST NIRCam Grism Spectroscopy Open
Dwarf galaxies hold the key to crucial frontiers of astrophysics, however, their faintness renders spectroscopy challenging. Here we present the JWST Cycle 2 survey, All the Little Things (ALT, PID 3516), which is designed to seek late-for…
View article: The Rise of the r-process in the Gaia-Sausage/Enceladus Dwarf Galaxy <sup>∗</sup>
The Rise of the r-process in the Gaia-Sausage/Enceladus Dwarf Galaxy <sup>∗</sup> Open
Neutron star mergers (NSMs) produce r -process elements after a time-delayed inspiral process. Once a significant number of NSMs are present in a galaxy, r -process elements, such as Eu, are expected to significantly increase with time. Ye…
View article: The R-process Alliance: Fifth Data Release from the Search for R-process-enhanced Metal-poor Stars in the Galactic Halo with the GTC*
The R-process Alliance: Fifth Data Release from the Search for R-process-enhanced Metal-poor Stars in the Galactic Halo with the GTC* Open
Understanding the abundance pattern of metal-poor stars and the production of heavy elements through various nucleosynthesis processes offers crucial insights into the chemical evolution of the Milky Way, revealing primary sites and major …
View article: Discovery of a Metal-poor Red Giant Star with the Highest Ultralithium Enhancement
Discovery of a Metal-poor Red Giant Star with the Highest Ultralithium Enhancement Open
We present the discovery of 2MASS J05241392−0336543 (hereafter J0524−0336), a very metal-poor ([Fe/H] = −2.43 ± 0.16), highly r -process-enhanced ([Eu/Fe] = +1.34 ± 0.10) Milky Way halo field red giant star, with an ultrahigh Li abundance …
View article: The R-Process Alliance: 2MASS J22132050–5137385, the Star with the Highest-known r-process Enhancement at [Eu/Fe] = +2.45*
The R-Process Alliance: 2MASS J22132050–5137385, the Star with the Highest-known r-process Enhancement at [Eu/Fe] = +2.45* Open
We present stellar parameters and chemical abundances of 47 elements detected in the bright ( V = 11.63) very metal-poor ([Fe/H] = −2.20 ± 0.12) star 2MASS J22132050−5137385. We observed this star using the Magellan Inamori Kyocera Echelle…
View article: The R-Process Alliance: 2MASS J22132050-5137385, the Star with the Highest-known r-process Enhancement at [Eu/Fe] = +2.45
The R-Process Alliance: 2MASS J22132050-5137385, the Star with the Highest-known r-process Enhancement at [Eu/Fe] = +2.45 Open
We present stellar parameters and chemical abundances of 47 elements detected in the bright (V = 11.63) very metal-poor ([Fe/H] = -2.20 +- 0.12) star 2MASS J22132050-5137385. We observed this star using the Magellan Inamori Kyocera Echelle…
View article: The <i>R</i>-Process Alliance: Analysis of limited-<i>r</i> stars
The <i>R</i>-Process Alliance: Analysis of limited-<i>r</i> stars Open
Context. In recent years, the R -Process Alliance (RPA) has conducted a successful search for stars that are enhanced in elements produced by the rapid neutron-capture ( r -)process. In particular, the RPA has uncovered a number of stars t…
View article: The oldest stars with low neutron-capture element abundances and origins in ancient dwarf galaxies
The oldest stars with low neutron-capture element abundances and origins in ancient dwarf galaxies Open
We present a detailed chemical abundance and kinematic analysis of six extremely metal-poor (−4.2 ≤ [Fe/H] ≤−2.9) halo stars with very low neutron-capture abundances ([Sr/H] and [Ba/H]) based on high-resolution Magellan/MIKE spectra. Three…
View article: Signatures of Tidal Disruption of the Hercules Ultrafaint Dwarf Galaxy*
Signatures of Tidal Disruption of the Hercules Ultrafaint Dwarf Galaxy* Open
The Hercules ultrafaint dwarf galaxy (UFD) has long been hypothesized to be tidally disrupting, yet no conclusive evidence has been found for tidal disruption owing partly to difficulties in identifying Hercules member stars. In this work,…