About

Blakesley Burkhart is an Associate Professor in the Department of Physics and Astronomy at Rutgers University. She is a member of the Graduate Faculty and specializes in astrophysics. Her research has led to notable achievements including the discovery of Eos, a vast molecular cloud near the Solar System, and she has been recognized with several awards such as the 2023-2024 Board of Trustees Research Fellowship for Scholarly Excellence, the APS 2022 Maria Goeppert Mayer Award, and the Annie Jump Cannon Award of the American Astronomical Society. Burkhart has also been promoted to Associate Professor and has been named a Sloan Fellow and a Packard Fellow, highlighting her significant contributions to her field.

Research topics

• Astrophysics
• Astronomy
• Physics

Selected publications

• Radiative Feedback in Population III Protostellar Growth: The Impact of HI Shielding

  arXiv (Cornell University) · 2026-03-31

  preprintOpen access

  We present a suite of radiation-magnetohydrodynamics simulations from the POPSICLE project that follow the long-term growth (~50 kyr) of primordial protostars while self-consistently coupling radiation, turbulence, and magnetic fields. The simulation suite is designed to quantify the relative impacts of the pathways of radiative feedback in Pop III stars - the extreme-ultraviolet (EUV) ionization and Lyman-Werner (LW) dissociation - by considering simulations with and without their inclusion. We find that without HI shielding, LW feedback alone can suppress and ultimately terminate accretion. With HI shielding, the large column densities near the protostar significantly weaken LW feedback. In the polar direction, atomic hydrogen fully shields LW radiation where $H_2$ self-shielding alone is insufficient. This leads to lower gas temperatures near the protostar and higher accretion rates, yielding larger final stellar masses than in models without shielding. The HII regions remain compact and confined to less than about 100 AU measured outward from the sink accretion radius (75 AU) due to high gas densities and continuous gas replenishment that inhibit the thermal pressure-driven breakout of the ionization front even for high ionizing luminosities. These results demonstrate that the interplay of gas dynamics, shielding, and radiative feedback can significantly alter the growth of Pop III stars. We discuss the implications for the initial mass function of primordial stars and the influence of feedback from early stellar populations.

  PublisherDOI

• Exploring the Impact of Active Galactic Nucleus Feedback Model Variations on the Ly <i>α</i> Forest Flux Power Spectrum

  The Astrophysical Journal · 2026-04-27

  articleOpen access

  Abstract We study the effects of varying different active galactic nucleus (AGN) feedback parameters on the Ly α forest 1D transmitted flux power spectrum (P1D). We use the Cosmology and Astrophysics with MachinE Learning Simulations suite to explore variations on the Simba simulation AGN feedback model. The parameters explored include the AGN momentum flux, AGN jet speed, supermassive black hole (SMBH) radiative efficiency, jet velocity threshold, and minimum SMBH mass needed to produce jet feedback. Although all parameters affect the P1D, this work explores the radiative efficiency, jet velocity threshold, and minimum SMBH mass in this context for the first time and finds the following results. Primarily, the most massive SMBHs impact the Ly α forest through the jet feedback mode. While heating AGN jets to the virial temperature at injection aids in the removal of neutral hydrogen from the Ly α forest, this heating also inhibits further jet feedback. Similar behaviors are seen when varying the SMBH radiative efficiency, with higher values resulting in a suppression of the SMBH growth and thus a later reduction in the AGN feedback and lower values directly reducing the impact of the AGN feedback on the Ly α forest P1D. These results imply that increasing the AGN feedback strength in the Simba simulation model suppresses the Ly α forest P1D, but only if the feedback does not impact the number of massive-jet-producing BHs. Future studies of AGN feedback models will require careful exploration of the unique aspects of the specific subgrid model, and how they interact with one another, for a complete understanding of the potential astrophysical impacts of SMBH feedback.

  PublisherDOI

• Implications of the nanoHertz Gravitational-Wave Background for Galactic Feedback and Massive Black Hole Growth

  Open MIND · 2026-02-17

  preprint

  We investigate how pulsar timing array (PTA) measurements of the nanoHertz gravitational-wave background (GWB) can constrain models for the growth history of supermassive black holes (SMBHs) and how active galactic nucleus (AGN) and stellar feedback models can affect GWB predictions. Feedback regulates supermassive black hole (SMBH) growth, altering the black hole mass function (BHMF). Using BHMFs drawn from multiple cosmological simulation suites including IllustrisTNG, MillenniumTNG, Simba, and CAMELS, and combining these with a quasar-based SMBH binary population framework, we predict the resulting GWB amplitude under a range of different stellar and AGN feedback prescriptions. We find that the choice of both stellar and AGN feedback models alters the high-mass end of the BHMF and changes the predicted GWB amplitude by up to a factor of 2 for the fiducial simulations and a factor 10 for extreme feedback variations in CAMELS. Models with inefficient or absent AGN feedback produce abundant SMBHs and yield GWB amplitudes consistent with PTA data, yet fail in producing realistic galaxies. Fiducial models of AGN and stellar feedback suppress SMBH growth too much and under-predict the expected signal, an effect which could possibly be mitigated by more realistic black hole seeding and growth prescriptions. The mismatch between the GWB amplitudes predicted by cosmological simulations and those observed by PTAs suggests that SMBH growth is more efficient or occurs earlier than captured by current models. This demonstrates that PTA measurements provide a powerful new probe of feedback physics and the SMBH population.

  DOI

• Radiative Feedback in Population III Protostellar Growth: The Impact of HI Shielding

  ArXiv.org · 2026-03-31

  articleOpen access

  We present a suite of radiation-magnetohydrodynamics simulations from the POPSICLE project that follow the long-term growth (~50 kyr) of primordial protostars while self-consistently coupling radiation, turbulence, and magnetic fields. The simulation suite is designed to quantify the relative impacts of the pathways of radiative feedback in Pop III stars - the extreme-ultraviolet (EUV) ionization and Lyman-Werner (LW) dissociation - by considering simulations with and without their inclusion. We find that without HI shielding, LW feedback alone can suppress and ultimately terminate accretion. With HI shielding, the large column densities near the protostar significantly weaken LW feedback. In the polar direction, atomic hydrogen fully shields LW radiation where $H_2$ self-shielding alone is insufficient. This leads to lower gas temperatures near the protostar and higher accretion rates, yielding larger final stellar masses than in models without shielding. The HII regions remain compact and confined to less than about 100 AU measured outward from the sink accretion radius (75 AU) due to high gas densities and continuous gas replenishment that inhibit the thermal pressure-driven breakout of the ionization front even for high ionizing luminosities. These results demonstrate that the interplay of gas dynamics, shielding, and radiative feedback can significantly alter the growth of Pop III stars. We discuss the implications for the initial mass function of primordial stars and the influence of feedback from early stellar populations.

  PublisherOA PDF

• A cosmological framework for stellar collisions at high redshift in proto-globular clusters, nuclear star clusters, and Little Red Dots

  arXiv (Cornell University) · 2026-03-27

  articleOpen access

  Observations and cosmological simulations indicate that the early Universe hosted numerous compact, high-density stellar systems, where close encounters and physical collisions between stars were likely common. We develop a bottom-up framework for stellar dynamics in such environments, spanning systems with and without intermediate- and supermassive black holes, and covering regimes where stellar collisions may or may not dominate the evolution. This radially-resolved analytic model connects dense star clusters in their cosmological context to observable outcomes mediated by stellar collisions. Initial conditions and environmental properties are drawn from high-resolution cosmological simulations, enabling exploration across a broad region of parameter space. The analytic predictions are validated against Monte Carlo simulations, demonstrating good agreement across key regimes. We find that stellar collisions are ubiquitous in many high-redshift environments, with runaway sequences naturally leading to the formation of very massive stars at early times. Finally, we show that high rates of destructive collisions can rapidly build up extremely dense gaseous environments around massive black holes, potentially providing an analogue to the observed population of Little Red Dots.

  PublisherOA PDF

• Implications of the nanoHertz Gravitational-Wave Background for Galactic Feedback and Massive Black Hole Growth

  arXiv (Cornell University) · 2026-02-17

  articleOpen access

  We investigate how pulsar timing array (PTA) measurements of the nanoHertz gravitational-wave background (GWB) can constrain models for the growth history of supermassive black holes (SMBHs) and how active galactic nucleus (AGN) and stellar feedback models can affect GWB predictions. Feedback regulates supermassive black hole (SMBH) growth, altering the black hole mass function (BHMF). Using BHMFs drawn from multiple cosmological simulation suites including IllustrisTNG, MillenniumTNG, Simba, and CAMELS, and combining these with a quasar-based SMBH binary population framework, we predict the resulting GWB amplitude under a range of different stellar and AGN feedback prescriptions. We find that the choice of both stellar and AGN feedback models alters the high-mass end of the BHMF and changes the predicted GWB amplitude by up to a factor of 2 for the fiducial simulations and a factor 10 for extreme feedback variations in CAMELS. Models with inefficient or absent AGN feedback produce abundant SMBHs and yield GWB amplitudes consistent with PTA data, yet fail in producing realistic galaxies. Fiducial models of AGN and stellar feedback suppress SMBH growth too much and under-predict the expected signal, an effect which could possibly be mitigated by more realistic black hole seeding and growth prescriptions. The mismatch between the GWB amplitudes predicted by cosmological simulations and those observed by PTAs suggests that SMBH growth is more efficient or occurs earlier than captured by current models. This demonstrates that PTA measurements provide a powerful new probe of feedback physics and the SMBH population.

  PublisherOA PDF

• A cosmological framework for stellar collisions at high redshift in proto-globular clusters, nuclear star clusters, and Little Red Dots

  arXiv (Cornell University) · 2026-03-27

  preprintOpen access

  Observations and cosmological simulations indicate that the early Universe hosted numerous compact, high-density stellar systems, where close encounters and physical collisions between stars were likely common. We develop a bottom-up framework for stellar dynamics in such environments, spanning systems with and without intermediate- and supermassive black holes, and covering regimes where stellar collisions may or may not dominate the evolution. This radially-resolved analytic model connects dense star clusters in their cosmological context to observable outcomes mediated by stellar collisions. Initial conditions and environmental properties are drawn from high-resolution cosmological simulations, enabling exploration across a broad region of parameter space. The analytic predictions are validated against Monte Carlo simulations, demonstrating good agreement across key regimes. We find that stellar collisions are ubiquitous in many high-redshift environments, with runaway sequences naturally leading to the formation of very massive stars at early times. Finally, we show that high rates of destructive collisions can rapidly build up extremely dense gaseous environments around massive black holes, potentially providing an analogue to the observed population of Little Red Dots.

  PublisherDOI

• Observing Compact Population III Star Clusters and the Presence of Cosmic Streaming

  The Astrophysical Journal · 2026-01-23 · 1 citations

  articleOpen access

  Abstract The formation of the Universe’s first luminous stellar structures depends on the unique conditions at “Cosmic Dawn,” which are set by the underlying cosmological model and early baryonic physics. Observations suggest that high- z star clusters reached stellar surface densities above 10 5 M ⊙ pc −2 , suggesting scenarios where models predict that the ability of stellar feedback to counter gravitational collapse is severely limited. We investigate the first star clusters in a suite of AREPO simulations, which explore the capacity for ΛCDM halos to maximally form high-density systems without feedback. We include the effects of the supersonic baryon–dark matter streaming velocity, an effect that impacts gas density and distribution in early minihalos. We show that early star clusters can reach high densities even in regions of strong supersonic streaming, provided feedback is weak. We analyze the interplay of the stream velocity and the dynamical processes of structure formation, finding that JWST has the opportunity to detect the brightest, most massive objects in our computational box. The detection of individual z ≥ 12 Population III star clusters below 10 7 M ⊙ is challenging, although lensing could reveal these objects in rare configurations, especially if a top-heavy initial mass function is present. We find that accounting for baryonic clusters separately from dark matter halos complicates predictions for the faint end of the high- z UV luminosity function, with competing effects from the stream velocity and low-mass clusters outside of halos. Finally, we explore clustering of star clusters as a promising probe of the stream velocity in these systems.

  PublisherDOI

• Observing compact Pop III star clusters and the presence of cosmic streaming

  ArXiv.org · 2025-09-26

  preprintOpen access

  The formation of the Universe's first luminous stellar structures depends on the unique conditions at "Cosmic Dawn," which are set by the underlying cosmological model and early baryonic physics. Observations suggest that high-$z$ star clusters reached stellar surface densities above $10^5 M_\odot$ pc$^{-2}$, suggesting scenarios where models predict that the ability of stellar feedback to counter gravitational collapse is severely limited. We investigate the first star clusters in a suite of AREPO simulations, which explore the capacity for $Λ$CDM halos to maximally form high-density systems without feedback. We include the effects of the supersonic baryon-dark matter streaming velocity, an effect that impacts gas density and distribution in early minihalos. We show that early star clusters can reach high densities even in regions of strong supersonic streaming, provided feedback is weak. We analyze the interplay of the stream velocity and the dynamical processes of structure formation, finding that JWST has the opportunity to detect the brightest, most massive objects in our computational box. The detection of individual $z\geq12$ Pop III star clusters below $10^7M_\odot$ is challenging, although lensing could reveal these objects in rare configurations, especially if a top-heavy IMF is present. We find that accounting for baryonic clusters separately from dark matter halos complicates predictions for the faint-end of the high-$z$ UVLF, with competing effects from the stream velocity and low-mass clusters outside of halos. Finally, we explore clustering of star clusters as a promising probe of the stream velocity in these systems.

  PublisherOA PDFDOI

• EOS: hiding in plain sight

  Astronomy & Geophysics · 2025-09-30

  articleSenior author

  Abstract Our nearest molecular cloud has eluded detection until now – but why?

  PublisherDOI

Recent grants

• Collaborative Research: Stars from Clouds - Turbulence, Magnetic Fields and Dynamics of Forming Star Clusters

  NSF · $300k · 2020–2024

Frequent coauthors

• Greg L. Bryan

  118 shared

• Mark R. Krumholz

  70 shared

• Rachel S. Somerville

  Flatiron Health (United States)

  68 shared

• M. Orr

  Flatiron Institute

  57 shared

• Romeel Davé

  University of Edinburgh

  53 shared

• Christopher C. Hayward

  Flatiron Institute

  52 shared

• Lars Hernquist

  50 shared

• Shy Genel

  Columbia University

  49 shared

Awards & honors

• 2023-2024 Board of Trustees Research Fellowship for Scholarl…
• APS 2022 Maria Goeppert Mayer Award
• Sloan Fellows (with Jed Pixley)
• 2020 Packard Fellow
• Annie Jump Cannon Award of the American Astronomical Society